Gas Hydrates in the GeosystemStatus SeminarGEOMAR Research Centre Kiel 6-7 May 2002

Programme & Abstracts

GEOTECHNOLOGIENScience Report

No. 1

Gas Hydrates in the Geosystem

ISSN: 1619-7399

Natural gas hydrates as a potential (i) energy resource, (ii) factor in global climatechange and (iii) trigger of submarine geohazard have received wide internationalattention in the past years.

In Germany, the national gas hydrate programme “Gas Hydrates in the Geosystem”has been initiated in 2000 as part of the new R&D programme GEOTECHNOLO-GIES, financed by the Federal Ministry for Education and Research (BMBF) and theGerman Research Council (DFG). The gas hydrate programme promotes a betterunderstanding of the nature of hydrates, hydrate-bearing sediments, and the inter-action between the global methane hydrate reservoir and the world’s oceans andatmosphere. Research projects covering a wide spectrum of science and technolo-gy, including geology, biogeochemistry, geophysics, physical chemistry andmechanical engineering. These are carried out in close collaboration betweenvarious national and international partners from academia and industry. Field stu-dies are underway at the Cascadia Margin off western North America, in the BlackSea, the Mackenzie Delta of the northwestern Canadian Arctic, and off-shoreCentral-America and Central-Africa.

This abstract volume contains the presentations given during four topical sessionsof the first status seminar “Gas Hydrates in the Geosystem” held at the GEOMARResearch Centre in Kiel, Germany. The abstracts reflect the multidisciplinary appro-ach of the programme and provides an excellent overview of where current gashydrate research in Germany stands.

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The GEOTECHNOLOGIES programme is financed by the Federal Ministry

for Education and Research (BMBF) and the German Research Council (DFG)

GEOTECHNOLOGIENScience Report

Gas Hydrates in the GeosystemStatus SeminarGEOMAR Research Centre Kiel6-7 May 2002

Programme & Abstracts

No. 1

Number 1

Impressum

SchriftleitungDr. Alexander RudloffDr. Ludwig Stroink

© Koordinierungsbüro GEOTECHNOLOGIEN, Potsdam 2002ISSN 1619-7399

The Editors and the Publisher can not be held responsible for the opinions expressed and the statements made in the articles published, such responsibility resting with the author.

Die Deutsche Bibliothek – CIP Einheitsaufnahme

GEOTECHNOLOGIEN; Gas Hydrates in the Geosystem, Status Seminar, GEOMAR Research Centre Kiel,6-7 May 2002, Programme & Abstracts – Potsdam: Koordinierungsbüro GEOTECHNOLOGIEN, 2002(GEOTECHNOLOGIEN Science Report No. 1)ISSN 1619-7399

Bezug / DistributionKoordinierungsbüro GEOTECHNOLOGIENTelegrafenberg A614471 Potsdam, GermanyFon +49 0331-288 10 71Fax +49 0331-288 10 77www.geotechnologien.degeotech@gfz-potsdam.de

Preface

Natural gas hydrates have received wide inter-national attention because of their potentialeffects on human welfare. In Germany a national programme “Gas Hydrates in theGeosystem” was launched in 2000 as part ofthe new R&D Programme GEOTECHNOLOGIES.Goal of the programme is to improve our basicknowledge concerning the distribution andphysical/chemical nature of naturally occurringmethane hydrates.

In an initial phase (2000-2003) a total sum of€ 15 million will be invested by the FederalMinistry of Education and Research (BMBF) ona balanced portfolio of laboratory and fieldstudies, tool design and testing, and computermodel development.The currently funded investigations focus onfour key themes: (i) the quantification of che-mical and physical properties of natural gashydrates, (ii) the carbon cycle and the role of

hydrates in global climate forcing, (iii) thedevelopment of new technologies (e.g. sea-floor fluid flux measurements), and (iv) as trig-ger of submarine geohazards.

The main objective of the first status seminar“Gas Hydrates in the Geosystem” is to bringtogether the national gas hydrate communityto present their ongoing work and exchangeresults; because several projects are interlinkedand depend on each other’s progress. We verymuch welcome further visitors from Europeand overseas to share their results and inter-ests. To all of them, this meeting will provide alively forum to help define future goals and tostimulate ongoing collaborative efforts.

Ludwig StroinkErwin Suess

Table of Contents

Scientific Programme........................... 1 - 7

Abstracts of Oral Presentations and Posters (in alphabetical order) ....... 8 - 147

Authors’ Index................................. 148 - 151

Notes

1

Monday, 6 May 200210.00Registration and poster mounting

11.00 – 11.15Welcome

GLOBAL CARBON CIRCLE AND CLIMATE EFFECTS (E. SUESS)

11.15 – 11.30Boetius A. & MUMM working group: The enigmatic process of anaerobic oxidation of methane: first results of project MUMM

11.30 – 11.45Kasten S., Hensen C., Schneider R., Spieß V.: Geochemical relicts of gas hydrate dissociationin sediments of pockmark sites of the Congo Fan (CONGO)

11.45 – 12.00Michaelis W., Seifert R., and the shipboard scientific party of the GHOSTDABS cruise:Structures and processes at methane seeps of the Black Sea (GHOSTDABS)

12.00 – 12.15Seifert R., Nauhaus K., Thiel V., Blumenberg M., Widdel F., Michaelis W.: Biomarkers and biogeochemical activity in methane fed microbial mats of the Black Sea (GHOSTDABS)

12.15 – 12.30Bohrmann G. & METEOR 52/1 cruise participants: Mud volcanoes and gas hydrates in theBlack Sea – an important linkage to the methane cycle (OMEGA, INGGAS)

12.30 – 12.45Wallmann K., Bohrmann G., Drews M., Suess E.: Fluid-geochemistry of active mud volcanoes in the Black Sea (OMEGA)

12.45 – 13.00Haeckel M., Suess E., Wallmann K., Rickert D.: Gas hydrate dynamics – Modelling hydrateformation in near surface sediments

13.00 – 14.00Lunch break

Scientific programme of the status seminar„Gas Hydrates in the Geosystem“ at GEOMARResearch Centre Kiel:

2

14.00 – 14.15Reichel Th., Halbach P., Holzbecher E.: Tectonically induced migration of the sulfate-methane-reaction zone in marine sediments of the Sea of Marmara - a case study (GHOSTDABS)

14.15 – 14.30Eisenhauer A., Teichert B.M.A., Bohrmann G., Liebetrau V., Linke P.: AuthigenicCarbonates in a Cold Seep Environment: Sensitive Recorders of Rapid Anoxia and SealevelChanges Determined by U- and Th-isotope Measurements (LOTUS)

TECHNOLOGICAL AND METHOLOGICAL DEVELOPMENTS (J. ERZINGER)

14.30 – 14.45Amann H., Hohnberg H.-J.: Autoclave sampling and in-situ preservation system, status andoutlook, March 2002 (OMEGA)

14.45 – 15.00Linke P., Pfannkuche O., Gust G., Sommer S., Gubsch S., Poser M., Greinert J.: Status ofdevelopment of long-term observatories for gas hydrate research within the collaborative project LOTUS

15.00 – 15.15Gubsch S., Viergutz T., Gust G., Müller V., Holscher B.: An in-situ laboratory array for biogeochemical processes under deep sea conditions with and without fluid venting (LOTUS)

15.15 – 15.30Reston T., Gajewski D., Hübscher C., Flüh E., Bialas J., Villinger H., Theilen Fr., and theINGGAS Group: An Introduction to INGGAS: INtegrated Geophysical characterisation andquantification of GAS hydrates

15.30 – 15.45Villinger H., Gennerich H.-H., Grevemeyer I., Kaul N.: INGGAS-Flux: New tools for energyand fluid-flux: pore pressure and thermal gradient probes

5.45 – 16.00Breitzke M., Bialas J., and INGGAS working group: A Deep-Towed Digital MultichannelSeismic Streamer for Very High-Resolution Studies of Marine Subsurface Structures - SystemDevelopment and First Results of RV Sonne Cruise SO162 (INGGAS Test)

16.00 – 16.30Coffee break

16.30 – 18.00Short presentation of the posters

18.00 – 19.15Poster show

approx. 19.30Dinner in the Kantine of GEOMAR

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Tuesday, 7 May 2002

TECHNOLOGICAL AND METHOLOGICAL DEVELOPMENTS (M. BREITZKE)

08.30 – 08.45Weber M.H. & the Mallik working group: Mallik 2002: An In-situ Gas Hydrate Laboratory

08.45 – 09.00Bauer K., Pratt R.G., Weber M.H., Harris J.M., Shimizu S., and the Mallik workinggroup: Crosshole seismic monitoring before and during a gas hydrate stimulation test

09.00 – 09.15Wiersberg T., Zimmer M., Schicks J., Dahms E., Erzinger J., and the Mallik workinggroup: Real-time mud gas monitoring at Mallik 4L-38 and 5L-38 wells

09.15 – 09.30Löwner R., Conze R., Wächter J., Krysiak F., Laframboise R., and the Mallik workinggroup: Mallik 2002: The Mallik Data and Information System

09.30 – 09.45Schultz H.J., Deerberg G., Schlüter S., Fahlenkamp H.: Simulation of the oceanic gashydrate removal using the mammoth-pump-principle (550 A)

QUANTIFICATION AND CHARACTERISTICS OF GAS HYDRATES (H. VILLINGER, W.F. KUHS)

09.45 – 10.00Kuhs W.F., Klapproth A., Itoh H., Goreshnik E.: Physico-chemistry and properties of gas hydrates : Preliminary answers to some open questions

10.00 – 10.15Klaucke I., Weinrebe W., Bohrmann G.: Geoacoustic mapping of near-surface gashydrates and associated features in the Black Sea using deep-towed, high-resolution sidescan sonar(OMEGA)

10.15 – 10.30Brückmann W., Linke P., Mörz T., Türk M., Poser M.: In-Situ Characterization of GasHydrates (OMEGA)

10.30 – 10.45Steffen H., Gust G.: Experimental and theoretical concepts to quantify deep-sea environmentsin an Autoclaved Experimental Chamber (AEC) (OMEGA)

10.45 – 11.15Coffee break

4

11.15 – 11.30Erzinger J. (co-ordinator), Spangenberg E., Schicks J., Naumann R., Lüders V., Möller P.,Kukowski N.: Experimental determination of physical and physico-chemical properties of gashydrate-bearing sediments (Project 555A- Overview)

11.30 – 11.45Schicks J., Lüders V., Möller P.: Raman Spectroscopic measurements of gas hydrates (555 A)

11.45 – 12.00Baumert J., Gutt C., Press W., Tse J., Janssen S.: Dynamics of Gas Hydrates (551 A)

12.00 – 12.15Müller C., Bönnemann C., Neben S.: Detailed Seismic Study of a Gas Hydrate DepositOffshore Costa Rica (DEGAS)

12.15 – 12.30Lüdmann T., Wong H.K., Konerding P.: A first estimate of the volume of methane gas associated with gas hydrate occurrence in the Dnieper Canyon area, northwestern Black Sea(GHOSTDABS)

12.30 – 12.45Grupe B., Kreiter S., Feeser V., Hoffmann K., Becker H.J., Savidis S., Schupp J.: SlopeStability and Land Slides in the Deep Sea: Influence Parameter Gas Hydrates (GASSTAB)

12.45 – 13.00Zühlsdorff L., Spieß V., Schwenk T., Chapman N.R., Riedel M., Hyndman R.D.: Multi-Frequency Seismic Data in the Vicinity of a Gas Hydrate Site at the Northern CascadiaAccretionary Prism (LOTUS)

13.00 – 14.00Lunch break

14.00 – 15.00Closing session & final discussion

ca. 15.00End of the meeting

5

POSTER PRESENTATION

GLOBAL CARBON CIRCLE AND CLIMATE EFFECTS

1. Krüger M., Treude T., Nauhaus K., Eppelin A., Boetius A., Widdel F.: Microbial methane turnover in different types of marine sediments – The MUMM-Project

2. Treude T., Boetius A., Knittel K., Rickert D.: Anaerobic oxidation of methane above gas (MUMM)

3. Nauhaus K., Treude T., Gieseke A., Knittel K., Boetius A., Michaelis W., Widdel F.:Massive Structures in the anoxic Black Sea: Biomass and carbonate formation based on theanaerobic oxidation of methane (MUMM)

4. Knittel K., Boetius A., Lemke A., Amann R.: Molecular Ecology of Anaerobic Oxidationof Methane (BMBF/Geotechnologien project ”MUMM”)

5. Lösekann T., Nadalig T., Knittel K., Boetius A., Sauter E., Schlüter M., Klages M.,Amann R.: Distribution of Methanotrophic Microbial Communities at the Haakon MosbyMud Volcano (MUMM project)

6. Niemann H., Elvert M., Boetius A.: Biomarker evidence of methane oxidation in sediments of Haakon Mosby Mud Volcano (MUMM)

7. Seifert R., Blumenberg M., Pape T., Peterknecht K., Thiel V., Schmale O., SültenfußJ., Rhein M., Michaelis W.: Gases and dissolved carbon compounds in the north-westernBlack Sea – concentrations and isotopic compositions (I + II) (GHOSTDABS)

8. Fischer H., Richter K.-U.: The role of gas hydrates in the course of rapid climate changes- Isotopic studies on methane in polar ice cores (549 A)

9. Mangelsdorf K., Dieckmann V., Wilkes H., Horsfield B., and the Mallik working group: Deep microbial ecosystem: biogeochemical characterisation and itspotential substrate feedstock (Mallik Research Well 5L-38)

10. Luff R., Wallmann K.: Biogeochemical turn over in methane rich sediments at HydrateRidge, Cascadia Margin: Quantification using a model approach (LOTUS)

11. Drews M., Schmaljohann R., Aloisi G., Wallmann K.: Microbiological and geochemical investigations at gas hydrate sites in the Black Sea (OMEGA)

TECHNOLOGICALl AND METHOLOGICAL DEVELOPMENTS

12. Drews M., Holscher B., Gust G., Wallmann K.: Gas hydrate formation and dissolution experiments in a pressure chamber (OMEGA)

13. Sommer, S., Pfannkuche, O., Linke, P., Gust, G., Gubsch S.: A novel benthic chamberfor long-term in situ observation and experiments (LOTUS)

14. Löwner R., Conze R., Wächter J., Krysiak F., Laframboise R. and the Mallik workinggroup: Mallik 2002: The Mallik Data and Information System

15. Schultz H.J., Deerberg G., Schlüter S., Fahlenkamp H.: Program for the simulation ofgas hydrate equilibrium (550 A)

16. Schmidt-Brauns J., de Beer D.: Development of a Methane Biomicrosensor for Deep SeaApplications (MUMM)

17. Mörz T., Brückmann W., Linke P., Türk M., Poser M.: HDSD – Hydrate Detection andStability Determination - A Tool For In-Situ Gas Hydrate Destabilisation (SFB 574)

18. Theilen Fr., Klein G., Thießen O., Schmidt M., Bohlen T.: NATLAB: Seismic Parametersand Physical Properties of Marine Sediments (INGGAS)

19. Gennerich H.-H., Grevemeyer I., Kaul N., Villinger H.: INGGAS-Flux: New tools forenergy and fluid-flux: pore pressure and thermal gradient probes

20. Kulenkampff J., Spangenberg E., Naumann R.: Experimental methods for the laboratory investigation of gas hydrate containing sediments (555 A)

21. Greinert J., Keir R., Spieß V.: Quantification of dissolved and free methane at gas hydrateassociated cold vents: The use of lander and ship mounted hydro acoustic systems andmethane sensors

QUANTIFICATION AND CHARACTERISTICS OF GAS HYDRATES

22. Spangenberg E., Kulenkampff J.: Physical Properties of Hydrate Bearing Sediments (555 A)

23. Henninges, J., Schrötter J., Erbas K., Huenges E., and the Mallik working group:Temperature profiles during a gas hydrate production test (MALLIK)

24. Bönnemann C., Behain D., Meyer H., Neben S., Müller C.: Recent seismic investigations on gas hydrates at convergent margins by BGR

25. Spieß V., Zühlsdorff L., von Lom-Keil H., Schwenk T.: Imaging of the internal structureof fluid upflow zones with detailed digital Parasound echosounder surveys (LOTUS)

26. Bünz S., Mienert J., Andreassen K.: Gas hydrate reservoir characterization using multi-component wide-angle and ocean bottom cable seismic data

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27. Itoh H., Goreshnik E., Klapproth A., Kuhs W.F.: Structure and dynamics of gas hydrates: Recent results

28. Staykova D.K., Goreshnik E., Salamatin A.N., Kuhs W.F.: Formation Kinetics of PorousGas Hydrates

29. Bohrmann G., Suess E., Kuhs W.F., Rickert D., Gunkel T., Techmer K., Heinrich T.,Abegg F., Linke P., Wallmann K.: Properties of Sea Floor Methane Hydrates at HydrateRidge, Cascadia Margin (OMEGA)

30. Abegg F., Freitag J., Bohrmann G., Kipfstuhl S., Brückmann W.: Structures of GasHydrates (OMEGA)

31. Krastel S., Spieß V., Zühlsdorff L.: MARGASCH – Marine gas hydrates of the Black Sea:First results from a high resolution 3D multichannel seismic survey (LOTUS)

32. Lom-Keil H. von, Spieß V., Krastel S., Greinert J., Artemov Y.: Acoustical studies inthe water column in vicinity of Cold Vents and Mudvolcanoes (LOTUS)

ASSOCIATED THEMES

33. Hübner A., Halbach P.: Pyrite Crusts from the Black Sea: Mineralogy and Genesis (GHOSTDABS)

34. Reimer A., Peckmann J., Reitner J.: Methane-derived carbonate mineralisation in the northwestern Black Sea (GHOSTDABS)

8

Structures of Gas Hydrates

Geophysical methods provide information ongas hydrate distribution on a scale rangingfrom tenths of meters up to kilometers. Basedon cores from discrete locations the distribu-tion and properties of the hydrates can beinvestigated on a scale from meters down tomicrons. Within OMEGA subproject 2 we useX-ray computed tomographic (CT) imaging tolook at the small scale interaction of gas bub-bles, hydrates and sediment to be able to con-tribute to questions of quantification, structureand physical properties.

We have applied two different types of CTscanner. One scanner, normally used for medi-cal purposes, is used to investigate samples oftenths of a centimeter in one dimension andup to 1.6 m in the other dimension. Up to nowthe samples are all preserved in liquid nitrogenand are also scanned in deep frozen condition.The other scanner is a micro CT scanner fornon-destructive three-dimensional microscopy.The sample volume is limited to a size of30x20.5 mm3. The scanner is located in theAWI-Bremerhaven in a cold laboratory with apermanent temperature of –25°C.Samples from two different regions have beenscanned. From R/V SONNE cruise 148 (projectTECFLUX, July/August 2000) to the HydrateRidge off the Oregon Coast a large set of 23gas hydrate samples, taken with a TV-guidedgrab sampler, is used. The second set of sam-ples has been taken during METEOR cruise 52to the Black Sea (project OMEGA and ING-GAS). The samples have been taken with gra-vity corer and TV-guided grab sampler.

In general the gas hydrates used in this studycan be grouped into three classes with certaintransitions. Without establishing a hierarchy,the first class consists of hydrates with large

bubble-like voids. Fig. 1 shows a wide space inthe sediment filled with an array of bubbles.The arch of the bubble skin, built from gashydrate, indicates the orientation during for-mation.The second group consists of dense non-homogeneous gas hydrate which has no bub-ble-like spaces and the third group to be men-tioned are gas hydrate layers alternating withsediment layers. These groups have been cho-sen for the sake of description but there are

also examples where transitions could be seenbetween groups in one sample. Subsequentdata processing of the scan data providesinformation about the percentages of gas, gashydrate and sediment within the sample.Besides samples with gas hydrate close to100%, the gas content may reach values ofabout 10%.

Abegg F. (1), Freitag J. (2), Bohrmann G. (1), Kipfstuhl S. (2), Brückmann W. (1)

(1) GEOMAR Research Center for Marine Geosciences, Wischhofstr. 1-3, 24148 Kiel, Germany

(2) Alfred Wegener Institute for Polar and Marine Research, Columbusstraße, 27568 Bremerhaven, Germany

Figure 1: CT slice indicating gas in white, gas hydrate in light gray, sediment in dark gray and black.

9

Autoclave sampling and in-situ preservationsystem, status and outlook, March 2002

Gashydrate research in the ocean needs auto-clave sampling and monitoring probes forgroundtruthing ephemeral gashydrates by pristine cores. In-situ conditions, first of allpres-sure but also temperature, sedimentmechanical properties and geochemistry, mustbe preserved in order to understand structure,formation, eventual uses and environmentalconditions of marine gashydrates. FachgebietMaritime Technik of Technische UniversitätBerlin, a partner in OMEGA, is developing suchtools, which, in addition, are being safety cer-tified by TÜV as pressure vessels. The Multi-Autoclave-Corer MAC takes four 50 cm longcores, diameter 100 mm, from the seafloor surface, by slow penetration and thus preser-ving the sediment structure. A 4 liter head-space for sea-floor- and downhole water con-stitutes a reservoir for in-situ chemical condi-tions. Figure 1 shows the engineering conceptbefore the last redesign in 2000. The ultimatehardware system will be presented on theStatus Symposium on May 6 in Kiel. DAPC is adynamic autoclave piston corer for 2m corerecovery, (Fig.2). Autoclave cores taken fromboth tools will be pressure stored onboard andthere will be scientific access opportunities forMAC cores, eg for pressurized subsampling.The main scientific investigation method of thein-situ core in the autoclave should be compu-ter tomography, CT, to xray the phase contents and possibly the in-situ sediment structure.

MAC and DAPC integrate a number of noveltechnical elements: a failsafe hingeless flap-valve to warrant the autoclave function indownhole conditions; a GRP pipe as transpa-rent pressure vessel (200 bar), complementedby an aluminium pipe segment as axial-tension

element, for CT analyses; a zero degree sea-water container, shielding the autoclave section for temperature control; an access portat the upper side for pressurized subsampling;avoidance of flanges for weight reduction andsmooth penetration; external seawater flowthrough the annulus to the cutting shoe tofacilitate coring; optionally and adapted from adifferent development project: a system formeasurement while sampling (salinity, tempe-rature, pressure, dissolved oxygen, pH, particlecontent).

MAC will be offshore tested on May 6 and 7,2002, with RV Alkor in the Baltic. Upon com-missioning during the same test cruise, it shallbe transported lateron to RV Sonne for theresearch cruise OTEGA on the Oregon HydrateRidge in July and August. Some subsystems ofthe DAPC, the autoclave piston corer, are avai-lable already. Upon a design review the systemis being redesigned during the forthcomingmonths. It shall be detail designed, manufac-tured and offshore tested until the first quarterof 2003. MAC and DAPC should be ready forstandard use, as scheduled, for gashydrateresearch and exploration projects in 2003.

Amann H., Hohnberg H.-J.

Technische Universität Berlin, FG Maritime Technik (MAT), Müller-Breslau-Straße VWS, 10623 Berlin, Germany

10

Figure 1: MAC, Multi-Autoclave-Corer, side view. Designed by MAT(Maritime Technik) TU BERLIN.

Figure 2: DAPC, Dynamic Autoclave Piston Corer.

Crosshole seismic monitoring before andduring a gas hydrate stimulation test (Mallikresearch wells 3L-38, 4L-38 and 5L-38)

To date, surface seismic data in combinationwith drilling results represent the most impor-tant source of information for mapping gashydrate occurrences in a regional to globalscale. However, qualitative and, much more,quantitative interpretation suffers from therelatively little knowledge on petrophysicalproperties of gas hydrate bearing sediments,and the limitations in resolution comparedwith the fine-scale strata and possible lensstructures as revealed from drilling hydratereservoirs (e.g., Dallimore et al., 1999). There-

fore, case studies are needed at well knownsites where direct borehole and petrophysicalcore analysis can be combined with seismicmeasurements for a wide range of scalelengths, to allow for scaling, from downhole tosurface seismic experiments. In that context,crosshole observations establish a missing linkbetween downhole logging on the one hand,and surface-borehole and surface measure-ments on the other hand (Figure 1), that was,to our knowledge, not covered in gas hydrateresearch so far.

Bauer K. (1), Pratt R.G. (2), Weber M.H. (1), Harris J.M. (3), Shimizu S. (4), and the Mallik working group

(1) GeoForschungsZentrum Potsdam

(2) Queen’s University at Kingston

(3) Stanford University

(4) Japan National Oil Corporation

Figure 1

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The Mackenzie Delta belongs to the best stu-died regions where gas hydrate accumulationsformed under permafrost conditions (e.g.,Dallimore et al., 1999, Majorowicz andOsadetz, 2001). The JAPEX/JNOC/GSC Mallik2L-38 gas hydrate research well provided awide variety of geological, geophysical andgeochemical information on the gas hydratebearing sediments at this location (Dallimore etal., 1999). Seismic properties including P andS velocities, and attenuation were deducedfrom downhole ultra-sonic and vertical seismicprofile (VSP) measurements (Collett et al.,1999, Guerin and Goldberg, 2001, Sakai,1999, Walia et al., 1999). Based on theseresults, several seismic experiments were pro-posed as part of the Mallik 3L-38, 4L-38 and5L-38 research wells to allow for a systematicseismic scaling study. The program includeddownhole ultra-sonic logging (Project leader(PL) United States Geological Survey (USGS),Japan National Oil Corporation (JNOC) andJapan Petroleum Exploration Company(JAPEX)), crosshole measurements (PL Geo-ForschungsZentrum (GFZ) Potsdam, togetherwith Queen's University at Kingston, StanfordUniversity, JNOC, JAPEX, and University ofKyoto), a VSP survey (PL University of Toronto),and a 3-D surface seismic experiment (PLUniversity of Alberta, Edmonton). Extensive geological and petrophysical core analysis willprovide an excellent base to substantiate inter-pretation of the resulting seismic images andparameter estimations.

In addition to seismic characterization at diffe-rent scale lengths, the main objective of theseismic experiments was to investigate the sui-tability of different seismic methods to monitorchanges of seismic properties related withthermal stimulation tests to produce methanegas from hydrates.

The crosshole seismic measurements were car-ried out by making use of two 1150 m deepobservation wells (Mallik 3L-38 and 4L-38)both 40 m from and co-planar with the 1170m deep production test well (5L-38). The pro-gram included one baseline survey before and

3 repeat surveys after the beginning of a ther-mal stimulation test. A high power piezo-cera-mic source was used to generate sweeped sig-nals with frequencies between 100 and 2000Hz that were recorded with arrays of 8 hydro-phones per depth level. During the baselineexperiment, the depth interval between 800 -1150 m was covered. A dense source andreceiver depth spacing was choosen as 0.75 mto increase spatial resolution. Angular coveragewas between 50 degrees against the hori-zontal axis. Based on tests, a stack of twosweeps per depth level during the initial expe-riment was adequate for acceptable signal-to-noise ratios. Acquisition parameters wereslightly adapted during the 3 monitoring expe-riments and a total depth interval between800 and 1050 m and one sweep per depthlevel were used.

First inspection shows that high quality datawere collected during the crosswell seismicexperiments. Initially, processing and modellingis focussed on the analysis of the baseline sur-vey data to derive high resolution seismic ima-ges characterizing the gas hydrate bearingsediments before starting the stimulation tests.First, very strong tube wave energy generatedin both observation wells had to be suppressedby multi-trace filtering in the source and recei-ver gather domain. The following data analysisis aimed to generate velocity models based onstandard travel time tomography and, toachieve higher resolution, full waveform inver-sion techniques (Pratt, 1999). Further proces-sing will include attenuation tomography,reflection imaging and connectivity mappingusing guided waves. The resulting referencemodels will be interpreted together withresults from other geophysical experimentsand petrophysical core analysis and modeling.

+–

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References

Collett, T. S., Lewis, R. E., Lee, M. W., Uchida,T., Detailed evaluation of gas hydrate reservoirproperties using JAPEX/JNOC/GSC Mallik 2L-38 gas hydrate research well downhole well-log displays, In: Scientific results fromJAPEX/JNOC/GSC Mallik 2L-38 gas hydrateresearch well, Northwest Territories, Canada,(ed.) Dallimore, S.R., Uchida, T., and Collett,T.S., Geological Survey of Canada, Bulletin544, 295-311, 1999.

Dallimore, S. R., Collett, T. S., and Uchida, T.,Summary - Sommaire. In: Scientific resultsfrom JAPEX/JNOC/GSC Mallik 2L-38 gas hydra-te research well, Northwest Territories,Canada, (ed.) Dallimore, S.R., Uchida, T., andCollett, T.S., Geological Survey of Canada,Bulletin 544, 1-10, 1999.

Guerin, G, and Goldberg, D., Sonic waveformattenuation in Gas Hydrate-bearing sedimentsfrom the JAPEX/JNOC/GSC Mallik 2L-38 rese-arch well, Mackenzie Delta, Canada, submit-ted to J. Geophys. Res., 2001.

Majorowicz, J. A., and Osadetz, K. G., Gashydrate distribution and volume in Canada,AAPG Bull. 85, 7, 1211-1230, 2001.

Pratt, R. G., Seismic waveform inversion in thefrequency domain, Part 1: Theory and verifica-tion in a physical scale model, Geophysics, 64,3, 888-901, 1999.

Sakai, A., Velocity analysis of vertical seismicprofile (VSP) survey at JAPEX/JNOC/GSC Mallik2L-38 gas hydrate research well, and relatedproblems for estimating gas hydrate concen-tration. In: Scientific results from JAPEX/JNOC/GSC Mallik 2L-38 gas hydrate research well,Northwest Territories, Canada, (ed.) Dallimore,S.R., Uchida, T., and Collett, T.S.; GeologicalSurvey of Canada, Bulletin 544, 323-340,1999.

Walia, R., Mi, Y., Hyndman, R.D., and Sakai,A., Vertical seismic profile (VSP) in the JAPEX/JNOC/GSC Mallik 2L-38 gas hydrateresearch well. In: Scientific results fromJAPEX/JNOC/GSC Mallik 2L-38 gas hydrateresearch well, Northwest Territories, Canada,(ed.) Dallimore, S.R., Uchida, T., and Collett,T.S.; Geological Survey of Canada, Bulletin544, 341-355, 1999.

14

Dynamics of Gas Hydrates

Gas hydrates are a special class of inclusioncompounds, in which small hydrophobic guestmolecules or atoms are trapped in cages for-med by an ice-like host lattice of water mole-cules. In recent years the clathrate hydrateshave attracted considerable interest as largedeposits of methane hydrate have been foundon the oceanic sea floors. The methane gasstored in the hydrate deposits may serve asfuture energy supply whereas instabilities mayhave implications for the global climatethrough the release of large amounts ofmethane. Therefore, the understanding of thephysical properties of methane hydrate is ofgreat interest.As gas hydrates consist to 80% of hydrogenbonded water molecules the physical proper-ties are expected to be similar to those of ice Ih.This, however, is not true for the thermal con-ductivity, which is a factor 5 smaller at T<0ºC(0.5 W/Km) than in ice Ih and even more sur-prisingly displays a temperature dependencesimilar to that of glasses despite the crystallinecharacter of the clathrate hydrates [1]. Thisbehaviour may play an important role for themodelling and prediction of stability of conti-nental hydrates and hydrates in shallow arcticwater.In the case of the gas hydrates the guest-hostinteraction is weaker than the bond strengthof the cage structure. Nevertheless it is thishydrophobic interaction, which stabilises theice framework and is thought to be responsi-ble for a coupling between the localised lowfrequency vibrations of guest molecules andthe vibrations of the host lattice. The rattlingmodes of the encaged guest molecules cantherefore act as effective scattering centres for

the heat carrying phonons, reducing the ther-mal conductivity and leading to the glass-liketemperature dependence.We were able to confirm this coupling in ahigh-resolution inelastic incoherent neutronscattering experiment (IINS) on xenon hydrateby finding three distinct low frequency excita-tions at 2.05 meV, 2.87 meV, and 3.94 meV[2,3] (Fig. 1). Xe-hydrate has as methanehydrate the cubic structure I consisting of 6large and 2 small cages in the unit cell. As thetotal incoherent scattering cross section of thewater molecules exceeds the cross section ofthe xenon guest atoms by a factor 1000, theIINS signal arises from the H-atoms, thus onlydisplaying the density of states (DOS) of thehost lattice vibrations. Lattice dynamical calcu-lations show that the coupling can be des-cribed as a symmetry avoided crossing, whichleads to a strong optic behaviour of the acou-stic host lattice modes in the frequency regionof the localised xenon modes. As the Xe-atomsin the small spherical cage vibrate with the hig-hest frequency and in the larger ellipsoidalcage with two lower frequencies, this givesraise to the three observed peaks.We also report of IINS experiments on metha-ne hydrate focussing on its low frequencyvibrations. The experiments were performedwith partially deuterated samples. Due to thedeuteration of the host lattice only the modesof the encaged methane molecules are visiblein the spectra. A broad quasielastic back-ground from the rotational excitations of themethane molecules was observed. Further-more broad inelastic excitations were visible inan energy region from 4 meV to 15 meV witha distinct peak at 5.3 meV, which can be attri-

Baumert J. (1, 3), Gutt C. (2), Press W. (3), Tse J. (4), Janssen S. (5)

(1) IEAP, Universität Kiel, Germany

(2) Experimentelle Physik I, Universität Dortmund, Germany

(3) ILL, Grenoble, France

(4) NRC, Ottawa, Canada

(5) PSI, Villigen, Switzerland

15

buted to vibrations of the methane moleculesinside the cages. The broad excitations from 7meV to 13 meV probably also reflect the den-sity of states of the host lattice. This pointsagain towards a coupling between the guestand host vibrations.The temperature dependence of the guestmodes shows that the repulsive part of theguest-host interaction, which stabilises the iceframework, plays an important role in thecoupling mechanism. In both xenon andmethane hydrate the guest modes were foundto shift towards higher frequencies with incre-asing temperature. Therefore anharmonicterms should play a considerable role in theguest-host interaction.Another important physical property is thevelocity of sound of methane hydrate. Due tothe importance of the hydrate deposits, relia-ble means of hydrate detection as well as goodmodelling of hydrates in sediments are neces-sary. The modelling of the hydrates in sedi-ments requires the knowledge of both the ela-stic constants and the sound velocity, which isalso necessary as calibration for the seismicdetection techniques. So far no microscopicmeasurements on natural or synthesised sam-ples have been reported and access to thesequantities by macroscopic means is difficult. InBrillouin light scattering experiments therefraction index and cage occupancy has to becalculated or assumed. Additionally methanehydrate samples don't display the optimal opti-cal quality needed for well-defined measure-ments of the velocity of sound [4].Very recently we could determine the longitu-dinal velocity of sound of methane hydratedirectly from the dispersion of the longitudinalacoustic host lattice mode in an inelastic x-rayscattering experiment (Fig. 2). Both the opticguest mode, arising from the localised vibra-tions of the methane molecules inside thecages, and the longitudinal acoustic (LA) hostlattice mode are observable. The LA modedisplays about the same energy dispersion as afunction of the wavevectortransfer k as the LAmode in ice. From the dispersion an orienta-tionally averaged longitudinal velocity of soundof about 3900 m/s was derived [5], which is

somewhat higher than the values found inBrillouin light scattering experiments.The region where the two modes intersect isadditionally of special interest as it containsinformation about the mixing of the modesand thus the coupling of the guest and hostvibrations. The linewidth of the LA host latticemode furthermore yields information about thephonon lifetime in methane hydrate, which canbe related to the thermal conductivity.

Figure 1:IINS spectrum of Xe-hydrate (Xe 5.75 H2O) at T=100K.The three distinct low energy peaks at 2.05 meV, 2.87meV and 3.94 meV are due to the coupling of guest and host vibrations (FOCUS-spectrometer PSI).

Figure 2: The dispersion curve for methane hydrate at T=100K.The mode at 5 meV displays a strong optic behavior corresponding to the localized vibrations of the methanemolecules inside the water cages. In a first step, the velocity of sound was derived from the linear dispersionof the LA lattice mode.

16

References:[1] R.G. Ross, P. Anderson, G. Backstrom,Nature 290, 322 (1981)

[2] J.S. Tse, V.P. Shpakov, V.R. Belosludov, F. Trouw, Y.P. Handa, W. Press, Europhys. Lett.54, 354 (2001)

[3] C. Gutt, J. Baumert, W. Press, J.S. Tse, S. Janssen, J. Chem. Phys. 116, 3795 (2002)

[4] H. Kiefte, M.J. Clouter, R.E .Gagnon, J. Phys. Chem., 89 3103 (1985)

[5] J. Baumert, C. Gutt, H. Requardt, M. Krisch, W. Press, M. Müller, J.S. Tse to be published

17

Recent seismic investigations on gas hydratesat convergent margins by BGR

In the last years all marine seismic cruises ofBGR on convergent margins revealed depositsof gas hydrates. The standard analysis of thesedata begins with the mapping of the BSR (bot-tom simulating reflector) in the processedreflection seismic data to achieve an estimateof the minimal extension of the gas hydrates.The BSR is not in all cases clearly visible, it canbe masked by diffractions (in stacked data) orby reflections from complex structures. Alsohigh-reflective sedimentary sequences, parallelto the slope of the seafloor, can aggravate theidentification of the BSR. Finally, in the case ofgas hydrate without free gas trapped belowthe BSR can be very week or absent.

The second standard analysis tool is the deriva-tion of the heat flow from the depth parame-ters of the BSR at selected locations. This givesvaluable data for further analysis and interpre-tation.

The work of BGR with these data has a varietyof objectives: reservoir investigations, structu-ral studies, comparative studies to understandthe origin of the gas and to assess the role ofgas hydrates and the free gas beneath it as apossibly future energy source. The followingareas will be shortly discussed:

Active margin of Costa Rica (SO81, BGR cruises)

The convergent continental margin of CostaRica is an area with large known gas hydrateoccurrences. At this margin BGR undertook in1992 a 3D seismic survey and acquired 2D seis-mic data during several cruises. The mappingof the BSR (Fig. 1) from these data reveals five

different areas of gas hydrates and indicationsfor a strong variability of the heat flow. Thedistribution is controlled by tectonism, slopesand the roughness of the subducting crust.The 3D seismic data and high-resolution 2Ddata from cruise BGR99 are subject of a detai-led seismic study of a gas hydrate reservoirstudy (DEGAS project in the framework of theGeotechnologien program).

Sunda Arc (SO137 GINCO cruise)

The Sunda subduction zone formed theMentawai and the Java forearc basins. Gashydrates are observed mostly in boundaryparts of the basins and in the anticlinal struc-tures in depths between 1300 mbsl and 3800mbsl (Fig. 2). In the center of the basins theBSR is either weak, obscured or totally absent.The derived heat flow in the basis ranges bet-ween 35 and 44 mW/m2. The values at theboundaries are much higher which could beexplained by fluid circulation.

Active margin of middle Chile (SO161 SPOC)

Gas hydrate has been observed only in thesouthern part of the working area of the SPOCcruise. They occur mainly on the middle slopeand are formed in lenghty patches parallel tothe coast.

Continental margin off Sabah (South China Sea)

The nature of this margin is still under discus-sion. Some authors believe that it is since postearly Middle Miocene an inactive continentalmargin. Gas hydrates occurrences were found

Bönnemann C. (1), Behain D. (2), Meyer H. (1), Neben S. (1), Müller C. (1)

(1) Bundesanstalt für Geowissenschaften und Rohstoffe, Stilleweg 2, 30655 Hannover

(2) Technische Universität Clausthal, Institut für Geophysik, Arnold-Sommerfeld-Straße 1, 38678 Clausthal-Zellerfeld

18

in depths between 1300 mbsl and 2800 mbsl.They occur mainly on the hanging walls andthe top of the anticlines in the Baram DeltaThrust Toe, the compressed thrust toe and thelower tertiary thrust sheets. Isotope analysesand thermal maturity modeling suggest a mix-ture of bacterial and thermal generation forthe gases inside the gas hydrates off NWSabah.

Figure 1: Stacked seismic section of line BGR99-54 at the activemargin of Costa Rica at seaward extension of BGR92 3Dbox across the Middle America Trench (MAT). A stromgBSR is recognizable approximately 0.2-0.55 TWT bsf. Thegeothermal gradients were estimated from BSR depths.

Figure 2:Distribution of gas hydrates at the Sunda arc, marked inlight blue.

19

The enigmatic process of anaerobic oxidationof methane: first results of project MUMM

Stable isotope signatures, radiotracer andmodeling techniques have established thatmost of the methane in marine sediments isoxidized microbially under anoxic conditions.This has been observed in the methane-sulfatetransition zone of subsurface sediments as wellas in surficial sediments of cold seeps, mud vol-canoes and above dissociating gas hydrates.As the major biological sink of methane inmarine sediments, the microbially mediatedanaerobic oxidation of methane (AOM) is cru-cial in its role of maintaining a sensitive balan-ce of our atmosphere’s greenhouse gas con-tent. However, details of the related biochemi-cal mechanisms and organisms are still largelyunknown. Understanding the geological, bio-logical and biochemical details of AOM is thegoal of our research group, in a combined eff-ort of biogeochemists, molecular ecologistsand microbiologists using novel analytical toolstailored for the study of unknown microbesand habitats. The discovery of Archea-SRBaggregates involved in the anaerobic oxidationof methane in gas hydrate sediments (GEO-MAR programmes TECFLUX I+II) has been amajor progress in the study of this process andhas shown the direction of future research.Under the umbrella of the project "MUMM"and in collaboration with colleagues within theMPI, the Alfred Wegener Institute for Polar andMarine Research, the GEOMAR, the UniversityBremen, the University of Hamburg, theUniversity of Georgia, the IFREMER and variousothers European and International partners,the biogeochemistry, molecular ecology and

microbiology of the process of anaerobic oxi-dation of methane and the microbial consortiainvolved are studied in different sedimentsystems. These include gas hydrates, coldseeps, mud vulcanoes as well as the omnipre-sent sulfate-methane interface of shelf sedi-ments. The goal is to understand the pathwayof methane oxidation through the consortiumand how the physiology and ecology of theinvolved microorganisms regulate the process.Experimental studies will be done on sedi-ments and enrichments to trace the fate ofmethane carbon and analyze the environmen-tal factors which determine the process rate.

During the first year of MUMM, we participa-ted in 5 expeditions including investigations ofmethane seeps in the Black Sea, gas hydratesand petroleum seeps in the Gulf of Mexico, anNorth-Atlantic mud volcanoe. We will furtherexplore methane production and breakdownin the seabed, and how efficiently the micro-bial sub-surface methane barrier controls theemission of this important greenhouse gas.Major new findings were achieved by allgroups involved in the project, some of whichare summarized below:

Presence of consortia of archaea and sul-fate reducing bacteria in gassy sediments(also see Knittel et al., this volume) The isotopic and genetic signature of themicrobial biomass in methane-saturated seepsediments shows that AOM is mediated by dif-ferent microbial consortia which generally

Boetius A. (1, 2, 3), Amann R. (1), de Beer D. (1), Elvert M. (1), Jørgensen B.B. (1),

Knittel K. (1), Krüger M. (1), Lemke A. (1), Lösekann T. (1), Nauhaus K. (1), Niemann H. (1), Schmidt J. (1),

Treude T. (1), Witte U. (1), Widdel F. (1)

(1) Max Planck Institute for Marine Microbiology, 28359 Bremen, Germany

(2) Alfred Wegener Institute for Polar and Marine Research, Am Handelshafen 12, 27515 Bremerhaven, Germany,

fon 49-471-4831-1518, fax 49-471-4831-1425, email: aboetius@awi-bremerhaven.de

(3) International University Bremen, 28725 Bremen, Germany

20

include archaea and sulfate-reducing bacteria.Fluorescence in situ hybridization revealed thatin all gassy sediments investigated, both archaeaand bacteria grow together in symbiotic associ-ation (Fig. 1). Among the archaea from thesesediments, rRNA probes target specifically twodifferent phylogenetic groups of archaea cap-able of mediating AOM: the ANME-2 group,belonging to the Methanosarcinales, and theANME-1 group, a new group of archaea onlydistantly related to the Methanosarcinales.

First in vitro demonstration of the processof AOM (also see Krüger et al., Treude etal. and Nauhaus et al., this volume).Sediment samples incubated under strictlyanoxic conditions in defined mineral mediumproduced sulphide from sulfate if methanewas added as the sole organic substrate. Nosulphide production occurred without methane.An increase of methane pressure resulted in anincrease of the sulfate reduction rate withsimultaneous production of sulphide at amolar ratio of nearly 1:1. The process itself pro-ved to be psychrophilic. The rates of methaneoxidation and sulfate reduction measured inshort-term experiments immediately after theretrieval of sediment samples on board of theships are generally reproducible in the long-term lab experiments. This project is carried

out in cooperation with the GEOMAR pro-grammes LOTUS and OMEGA).

Discovery of carbonate landscapes in theBlack Sea formed by massive microbialmats (see also Nauhaus et al., this volume).During submersible dives to methane seeps in

the permanently anoxic Black Sea, giant micro-bial structures were discovered, composed ofmassive microbial mats of centimeter to deci-meter thickness, producing large carbonatecolumns and platforms. Both the microbial bio-mass and the carbonates are partially derivedfrom methane as indicated by their depletionin 13C. The massive mats are mainly compo-sed of a consortium of archaea and sulfatereducing bacteria, which is responsible for highrates of methane oxidation via sulfate reduc-tion, and for methane incorporation intomicrobial biomass and carbonates. This projectis carried out in cooperation with theUniversity of Hamburg (progamme GHOST-DABS).

Methanotrophic consortia forming an effi-cient barrier against methane emission tothe hydrosphere (see also Lösekann et al.and Niemann et al., this volume).The Haakon Mosby Mud Volcano (HMMV) issituated on the continental slope northwest ofNorway at a water depth of 1250 m. Extensivemats of giant, sufide-oxidizing bacteria weredetected, indicative of a rapid production ofsulfide from methane via AOM. Beneath thesemats, a high biomass of consortia containingANME-2 archaea was found, obviously capableof oxidizing methane with sulfate at tempera-tures close to the freezing point (-1°C). Theconcentration of methane in the bottomwaters was extremely high in the center and atthe outer rim, but showed a significant dropabove the Beggiatoa mats, indicating that themethanotrophic consortia effeciently removemethane rising from the sediments to thehydrosphere. This project is carried out in coo-peration with the Alfred Wegener Institute forPolar and Marine Research and with the Frenchresearch institute IFREMER.

Figure 1. Consortia of archaea and sulfate reducing bacteria detected at MUMM study sites (K Knittel, A Boetius).

21

Mud volcanoes and gas hydrates in the BlackSea – an important linkage to the methanecycle (initial results from METEOR cruise MARGASCH M52/1)

METEOR cruise M52/1 (January 2 to February 1,2002; Istanbul – Sevastopol- Istanbul) carried outresearch on gas hydrates in the Black Sea. Theleg focused on the distribution, composition,and the structure of gas hydrate occurrences,and their relationship to fluid migration throughthe sediments and to gas venting. The environ-mental conditions for the formation of gashydrates in the Sorokin Trough and to less extentto the central Black Sea have also been the ofinterest. In both areas gas hydrates have beenreported from Russian scientists to occur close tothe seafloor. Such hydrates are highly reactivemethane reservoirs with extremely variablemethane fluxes. The approach used during thisleg was highly interdisciplinary and includedhigh-resolution geoacoustical investigations ofthe seafloor and subbottom using a wide rangeof frequencies and techniques, video mappingof the seafloor, investigations of the watercolumn, and sampling of sediments and gashydrates.

Mud volcanoes occur in the central Black Seaand Sorokin Trough (Fig. 1) in a great variety ofsizes (up to 2,5 km in diameter). The volcanosmay rise as much as 200 m above the seafloor.In the Sorokin Trough the roots of such mud vol-

canoes are connected to deeper diapiric structu-res that evolved in the compressional tectonicregime between the Tetyaev and Shatskiy Risesin the south and the Cremean Peninsula in thenorth. The diapiric folds are formed mostly byclay deposits of the Maikopian Formation(Oligocene-Lower Miocene) which enables fluidsand gases to migrate upwards to the seafloor.The methane gas either forms gas hydrate oremanates to the water column producing acou-stic plumes. Near-surface gas hydrates weresampled during the cruise from several mud vol-canoes known as Yalta, Dvurechenskii, Odessaand an unnamed mud volcano (Fig. 2). TheDvurechenskii mud volcano in particular is a see-page area with high fluxes. While the normalwater temperatures were about 9° C at the sea-floor, the upper 6 m sediment in the central partof Dvurechenskii mud volcano showed tempe-ratures of up to 16° C in. An higher temperatu-re anomaly was measured in the bottom waterwith the CTD mounted on the TV-sled. Thesehigh temperatures suggest that the mud is cur-rently rising. In spite of the high temperature, thepressure is high enough in 2000 m water depthto allow the formation of gas hydrates. Alle sixsedimentary cores from Dvurechenskii mudvolcano contained large amounts of finely

Bohrmann G. (1), Abegg F. (1), Aloisi G. (1), Artemov Y. (5), Bialas J. (1), Broser A. (1), Drews M. (1),

Fouchet J.-P. (6), Greinert J. (1), Heidersdorf F. (2), Ivanov M. (4), Blinova V. (4), Klaucke I. (1), Krastel S. (2),

Leder T. (2), Polikarpov I. (5), Saburova M. (5), Schellig F. (3), Schmale O. (3), Spieß V. (2), Volkonskaya A. (4),

Weinrebe W. (1), Zillmer M. (1)

(1) GEOMAR, Forschungszentrum Kiel, Germany

(2) Fachbereich Geowissenschaften der Uni Bremen, Germany

(3) Institut für Biogeochemie und Meereschemie, Universität Hamburg, Germany

(4) UNESCO-Center for Marine Geosciences MSU, Moskow, Russia

(5) A.O. Kovalevsky Institute of Biology of the Southern Seas, Sevastopol, Ukraine

(6) FREMER, Plouzané, France

22

dispersed gas hydrate that dissociated quickly onboard the research vessel. The pore water profi-les indicated a strong fluid and/or gas flux fromthe sediment to the water column. The CTD andwater sampling stations at Dvurechenskii mudvolcano were the only sites where higher metha-ne concentrations were measured in the bottomwater, indicating a strong methane flux from anactive mud volcano.

Seismic overview profiles over a large number ofmud volcanoes were conducted to define a tar-

get area for a 3D-seismic survey, which was thenperformed at the Sevastopol mud volcano. Anarea of 7 x 2.5 km was covered by high-resolu-tion reflection seismic work and OBS/OBH refrac-tion seismic studies in order to obtain detailedimages of the pathways that gases and fluidstake when moving upwards. In addition to pro-viding information about sedimentary layeringand tectonic processes, the combined data willhelp to quantify the spatial characteristics con-cerning the locations and the quantities of gashydrate enclosed in the sediment.

Figure 1: Locations of mudvolcanos in theSorokin Trough (Black Sea).

Figure 2: Sites of sampling duringMARGASCH cruiseM52/1 in theSorokin Trough(Black Sea).

23

Properties of Sea Floor Methane Hydrates atHydrate Ridge, Cascadia Margin (OMEGA)

Hydrate Ridge, at the Cascadia convergentmargin, harbors a variety of methane hydratesin near-surface sediments. On its southernsummit clathrates are exposed on the seafloorand are populated by a methane-oxidizingbacterial consortium that provides the drivingforce for high benthic biological activity andcarbonate precipitation. Here hydrates coexistwith bubbles of free methane gas, whichmigrates upwards from beneath the hydratestability zone. During several research cruiseswe recovered gas hydrate samples with a largevariety of fabrics. The samples show denseinterfingering of gas hydrate with soft

sediment. In most cases, pure white hydrateoccurs in layers several millimeters to severalcentimeters thick. Host sediment is often pre-sent as small clasts within the pure gas hydra-te matrix. On a macroscopic scale, the fabricvaries from highly porous (with pores of up to5 cm in diameter; Fig. 1A) to massive (Fig. 1B).

Bohrmann G. (1), Suess E. (1) , Kuhs W.F. (2), Rickert D. (1), Gunkel T. (1),

Techmer K. (2), Heinrich T. (2), Abegg F. (1), Linke P. (1), Wallmann K. (1)

(1) GEOMAR Research Center for Marine Geosciences, Kiel, Germany

(2) GZG Geological Center, University of Göttingen, Germany

Figure 1: Typical gas hydrate fabrics from sediments of southernHydrate Ridge. Highly porous hydrate framework (A)and massively layered, dense gas hydrate (B). Field-electron scanning micrograph from a macroscopic poroushydrate (C); FE-REM image from a dense hydrate specimen showing a homogenous distribution of nano-pores in the range of 100-400 nm.

24

Wet bulk densities of 80 pure hydrate samplesmeasured onboard RV SONNE range from 0.35g/cm3 to 7.5 g/cm3 and show a negative corre-lation between density and percentage of porespace (Fig. 2). Pore space was estimated fromthe change in volume before and after com-pression of each sample on a hydraulic press toapproximately 160 bar. The samples showhigh variability in pore volumes ranging from10-70 vol.% (Fig. 2). Fitting a line to the den-sity versus pore space data, we estimate theend-member density at zero porosity to beapproximately 0.81 g/cm3, which is 0.1 g/cm3

less than the theoretical material density ofpure methane hydrate (0.91 g/cm3). We attri-bute the difference in density to sub-micronporosity of the hydrates that cannot be mea-sured with the technique used for the determi-nation of pore volume. The sub-micron poro-sity (nano-porosity) is documented by a moreor less homogenous three-dimensional spon-ge-like texture observed by field-emissionscanning electron microscopy (Fig. 1D). Thesesub-micron pores have typical sizes of 100-400nm, and have been observed in both naturaland artificial gas hydrates.

The low bulk density of natural methanehydrates from Hydrate Ridge results in an enor-mous positive buoyancy force, implying thatthe hydrate remains on the seafloor onlybecause of the shear strength of the host sedi-ment. We speculate that slabs of hydrate maybreak off from the seafloor and rise to the seasurface, even when the hydrate is covered withsediment. We believe that the chaotic seafloortopography of small mounds and depressions,observed on southern Hydrate Ridge duringALVIN and ROPOS surveys, is result from thisprocess, which may constitute an importanttransport mechanism for methane from theseafloor to the atmosphere.

Figure 2: Bulk densities and pore volumes of 15 gas hydrate samples from Hydrate Ridge, measured onboard researchvessel SONNE during SO148.

25

A Deep-Towed Digital Multichannel SeismicStreamer for Very High-Resolution Studies of Marine Subsurface Structures - SystemDevelopment and First Results of RV SonneCruise SO162 (INGGAS Test)

The vertical and lateral resolution of marine sub-surface structures in reflection seismic imagesstrongly depends on the marine seismic sourceand streamer system used for signal generationand data acquisition. The vertical resolution iscontrolled by the dominant frequency andbandwidth of the reflected signals and can beimproved by using high(er)-frequency sourceslike GI- or waterguns in deep and boomers orsparkers in shallow water. Deconvolution tries toimprove the vertical resolution by increasing thebandwidth. The lateral resolution is determinedby the size of the Fresnel zone whose radiusdepends on the source and streamer depth andon the depth of the reflector, respectively, onthe velocity above the reflector and on thedominant frequency. Migration decreases thein-line resolution and radius of the fresnel zoneto minimum a quarter wavelength but has noinfluence on the cross-line resolution. The lattercan only be improved by lowering the streamerand - in the ideal case - the source towards tothe sea floor. This is the main objective of ING-GAS subproject 3.

During 2001, a hybrid multichannel digitaldeep tow seismic streamer has been developedin order to collect marine seismic data with animproved lateral in- and cross-line resolutionparticularly in regions of special interest for gashydrate research. In this context, hybrid systemmeans that conventional marine seismic sour-ces like air-, GI or waterguns shot close to the

surface will still be used, whereas the streameris lowered to the sea floor and - combinedwith a side scan sonar system acquired withinthe OMEGA project of the gas hydrate initiati-ve of the GEOTECHNOLOGIEN program -forms a deep-towed device. A depressor ofabout 2 tons weight completes the deep towsystem and ensures the side scan sonar andstreamer to keep in depth and as close to thetowing ship as possible (Fig. 1).

The streamer is a modular digital seismic array(HTI, High Tech, Inc.) which can be operated inwater depths up to 6000 m. It consists of a 50m lead-in cable towed behind the side scan

Breitzke M., Bialas J., and INGGAS working group

GEOMAR Research Centre for Marine Geosciences, Wischhofstrasse 1 - 3, 24148 Kiel, Germany,

mbreitzke@geomar.de, jbialas@geomar.de

Figure 1:Deep tow streamer and side scan sonar elements ready fordeployment on board RV Sonne.

26

sonar fish and single modules for each channel. Two different modules - acoustic andengineering modules - exist (Fig. 1). Each acou-stic module houses a single hydrophone and alow- and high-cut filter, preamplifier and 24-bitAD converter in a pressure vessel. Special engi-neering modules additionally include a compassand pressure sensor which provide informationon the depth of the module below sea surfaceand on its geographical position (heading).Modules are interchangeable and can arbitrarilybe connected by cables of 1 or 6.5 m length(Fig. 1). Up to 96 channels can be combined.Selectable sample intervals and preamplifiergains between 0.25 - 500 ms and 0 - 36 dB,respectively and two different high-pass filterswith 4 Hz low-cut frequency allow to use diffe-rent and sufficiently high-frequency seismicsources to guarantee both a very high verticaland lateral resolution. At this stage of develop-ment the streamer consists of 26 modules inclu-ding three engineering modules.

The exact depth and position of the side scansonar fish is determined by the ultra-short baseline (USBL) system POSIDONIA. It mainly con-sists of an acoustic array (antenna) installed inthe moon-pool and calibrated for its particularposition, and a responder mounted on the sidescan sonar fish and housing a pressure trans-ducer. The responder function is triggered viacable link through a linux-based gateway PCinto the coaxial or fibre optic sea cable byinterrogations from the POSIDONIA cabinet.Together with DGPS, gyro compass andmotion sensor information provided by theship the POSIDONIA system allows to determi-ne the depth and position of the side scansonar fish with an absolute accuracy of 1% ofthe water depth.

The depths, geographical positions and hea-ding values determined by the ultra-short baseline (USBL) system POSIDONIA and the threeengineering modules of the digital seismicstreamer are fed into a navigation program.Together with the DGPS based trigger timesthis program generates a shot table which pro-vides information on the depth and geogra-

phical position (latitude, longitude) of eachstreamer node at each shot/trigger time. Gyrocompass and motion sensor data from the shipand, possibly first break and multiple arrivaltimes contribute to this program, indirectly.During seismic profiling the shot table is storedon hard disc and thus serves as a log file whichallows to assign the exact source and receivergeometry to the seismic data header later offline, for subsequent data processing steps.

The deep tow seismic streamer and side scansonar system can be completely controlledfrom the top side by a linux-based gateway PC.At the bottom side a second linux-based PCwith 120 GB storage capacity and a telemetrysystem, which handles the data transfer bet-ween underwater and on board systems andprovide all necessary power supplies for thebottom electronics, are installed in a pressure-proofed housing mounted on the side scansonar fish.

The seismic are stored underwater on thelinux-based PC and are transmitted via ether-net to an on board PC running a GEOMETRICSStrata Visor quality control and data storageprogram. Two DLT devices are connected foran inifite data storage in daisy chain operation.Commands which control seismic recordingparameters like sample interval, record length,delay or preamplifier gain, and which initializethe data transfer between underwater and onboard systems, are sent from the top to thebottom side via low-speed downlink, whereasseismic and side scan sonar data are transfer-red from the underwater to the top side viatelemetry and high-speed uplink through acoaxial (RV Meteor) or fibre optic sea cable (RVSonne). Laboratory tests with a 5 and 11 kmlong coaxial cable, and experiences gainedduring the INGGAS test cruise SO162 with RVSonne have yielded sufficiently high data trans-fer rates (500 - 800 kByte/s) so that almost allcomplete shot gathers could be transferredonline from the bottom to the top side systemduring seismic profiling, allowing an onlinequality control of the complete data set.

27

All bottom and top side components and airgun shooting are synchronized by DGPS time-based trigger signals generated by the linuxgateway PC. Additionally, all components con-trolling the deep tow device are linked viaethernet and form a small PC cluster within thecomputer network on board the research ves-sel during each cruise.

The deep tow system has recently (21.02. -12.03.02) been tested in the Yaquina Basin offPeru during RV Sonne cruise SO162 (INGGASTest). A GI-gun of 0.7 l volume and a Prakla-type airgun of 1.6 l volume were used as high-frequency seismic sources. The first test profile,run along the strike of the Peruvian continen-tal margin in order to keep maneuvring of the75 m long (50 m lead-in, 25 1 m long cables)deep-towed streamer as simple as possible,showed a very high data quality and resolutionof the subsurface structures on the on-linedisplay. Observation of the depth (and hea-ding) data provided by the engineering modu-les showed a good agreement with the depthdata determined by the POSIDONIA system forthe side scan sonar fish and only slight depthvariations along the streamer length, so thatan accurate online control of the streamerposition is possible.

Variations of the ship velocity between 1.0 and4.0 kn demonstrated that the best results withthe lowest noise level could be achieved for avelocity of 3.0 kn. If the stability of the sidescan sonar fish and the reach of the acousticside scan sonar signals are simultaneouslytaken into account velocities up to 3.5 kn arealso acceptable at an optimum towing depthof 80 - 120 m above the sea floor.

A loss or severe distortions of the seismic sig-nals observed during winch operations andduring turns from one profile line to anothercould be identified as an overload of the pre-amplifiers caused by "fast" changes in waterdepth. A subsequent check of the gains actu-ally required during smooth normal seismic

profiling yielded that a preamplifier gain of 12dB is optimum for the high-frequency smallchamber sources used during this test cruise. A final survey along a grid of 11 closely spacedprofile lines covering an area where the "Maxand Moritz" chemoherms were discoveredduring RV Sonne cruise SO146 (GEOPECO)proved that the complete deep tow system canbe handled for such high-resolution 3D sur-veys. Turns from one profile line to another ofabout 600 m diameter could be operated sothat distances of about 100 m between neigh-bouring profile lines could be reached by anappropriate survey design. The seismic datarecorded along these lines show a very detai-led image of the chemoherms in this area.

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In-Situ Characterization of Gas Hydrates

An important issue in current gas hydrate research is the need for better tools to remotelyestimate of the volume of marine gas hydratein the near subsurface. Improving these estimates is of critical importance for determi-ning the global abundance of gas hydrate, forevaluating their importance for the stability ofcontinental slopes and their potential for economic exploitation.Our knowledge about the occurrence, spatialdistribution, and life-cycle of gas hydrates inmarine sediments is mainly derived from indi-rect geophysical and geochemical evidence.Namely pore water freshining, i.e. the degreeof Cl-depletion in interstitial water of marinesediments can be used to get a first-order estimate of hydrate abundance. In a fewinstances gas hydrates have also been directly observed or even sampled at the sea floor, e.g.at Hydrate Ridge off the Oregon coast and inmud volcanoes in the Black Sea. For regionalor global estimates of hydrate volumes howe-ver, new techniques for ground-truthing andcalibration of geophysical and geochemicalmethods are needed.As part of Cooperative Research Center (SFB)574 "Volatiles and Fluids in Subduction Zones"a new tool, HDSD (Hydrate Detection andStability Determination) is being developed toaddress this issue. HDSD is designed to identifyand quantify small volumes of near-surface gashydrate through continuous in situ thermaland resistivity monitoring in a defined volumeof sediment while it is slowly heated to de-stabilize gas hydrates embedded in it.In its current configuration HDSD is deliveredto the seafloor with a video-guided GEOMARBC Lander system. The sediment volume to betested for the presence and abundance of gashydrates is first isolated by a rectangular experiment chamber that is pushed into the

upper 30cm of sediment.A “stinger”, centrally mounted in the chamberand equipped with two arrays of sensors, provides the capability for monitoring the sedi-ment resistivity and temperature profile duringthe test. A computer-controlled electric hea-ting system and heat-exchange unit mountedon top of the chamber provides the means fortransferring energy into the sediment.In its initial configuration HDSD will be operating over a 24 to 36 h period in a two-step mode: after insertion the sensors will firstbe used to collect the undisturbed resistvityand temperature profile. During the secondphase a pre-programmed heating cycle is carried out to slowly destabilize any gas hydrate contained in the volume. The sensorarray is used to monitor the migrating tempe-rature wave and the change in pore fluid resistivity resulting from hydrate breakdown.This data together with well constrained initialPT conditions at the test site will be inverted ina thermodynamic phase model to yield thevolume and distribution of gas hydrate.The HDSD tool will be first deployed and testedin July 2002 during RV SONNE cruise 165(OTEGA) to Hydrate Ridge, were gas hydratesare abundant in the shallow subsurface. Forthe next stage of development additional sensors will integrated into the chamber toprovide enough data for resistivity tomo-graphy.

Brückmann W. (1), Linke P. (1), Mörz T. (1), Türk M. (1), Poser M. (2)

(1) GEOMAR Forschungszentrum für Marine Geowissenschaften, Kiel, Germany

(2) Oktopus GmbH, Hohenwestedt/Kiel, Germany

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Gas hydrate reservoir characterization usingmulti-component wide-angle and ocean bottom cable seismic data

SummaryOcean Bottom Seismometer and OceanBottom Cable data allow to assess the elasticproperties of hydrated and gassy sediments inan integrated approach. The study area is located north of the Storegga Slide sidewall in800 m – 1200 m water depth. Our data indi-cates variable concentrations of gas below thegas hydrates, which might result in locally confined zones of overpressure. Gas hydratesappear to occur in disseminated form and inlow concentrations, which do not allowcementing the sediment grains.

IntroductionUnderstanding the distribution and concentra-tion of marine gas hydrates is necessary toassess its role in slope stability, controlling global climate and as a possible future energyresource. Research in other areas indicates thatmulti-component studies together with addi-tional geotechnical data seem to be the bestapproach to study the nature of this reservoir(Guerin and Goldberg, 1999). Geophysical evi-dence for gas hydrates exists along the northern sidewall of the Storegga Slide (Figure1) (Mienert et al., 1998, Andreassen et al.,2000). A BSR reflects the base of the GasHydrate Stability Zone (GHSZ), and the free gaszone beneath it. High-resolution seismic dataabove the hydrated sediments reveals that theBSR amplitude is variable and in some placesthe BSR is only identified as an abrupt termi-nation of high-amplitude reflections under-neath. Such high-amplitude reflections areinterpreted as strata-bound free gas, whichaccumulates beneath less permeable layers(Bouriak et al, 2000). Results from the ocean

bottom cable data so far indicate that gashydrate do not cement the sediment(Andreassen et al., 2001). Furthermore there isno reflection from the gas below the hydrates,which points towards low gas concentrations.

Seismic dataIn this approach we commence a high-reso-lution evaluation of Vp/Vs-ratio and shear-wave velocity of the converted wave recordsfrom a 4 km long ocean bottom cable line andfrom 4 ocean bottom seismometer stations(Figure 1). The P-S data evaluation requires aspecial processing procedure to determine theVp/Vs-ratio and the shear-wave velocity of thesediments. To couple the converted-wave velo-cities to the determined p-wave velocitymodel, a different approach was applied usinga quasi Vp/Vs semblance method. In thisapproach velocities of the converted waveswere calculated from the p-wave model usingfixed Vp/Vs ratios. The resulting non-hyper-bolically moveout-corrected gathers were stak-ked to a single trace for each Vp/Vs-ratio. Theresulting traces were plotted as a seismic sec-tion. Within these sections the Vp/Vs ratiovaries from 1.7 to 7.7. Highest energies in suchsection occurs for Vp/Vs ratios for which thearrivals stack best. The results from this technique provide the starting models for ray-tracing and amplitude modeling.

Results and discussionThe compressional-wave velocity shows adistinctive increase just above the BSR and alow-velocity zone below the BSR. We interpretthese zones to be caused by hydrated and gas-charged sediments, respectively. Another low-

Bünz S., Mienert J., Andreassen K.

Department of Geology, University of Tromsø, Dramsveien 201, 9037 Tromsø, Norway

30

velocity zone occurs at about 250 m below theBSR, at the base of the Naust Formation. This isthe upper termination of a polygonal faultsystem and the base of a fluid leakage system inthe area. The magnitude of the velocity decrea-se, i.e. 200 – 300 m/s, is caused by free gas. TheVp/Vs-ratio decreases through the whole sedi-ment column from 7 for the uppermost sedi-ments to 5 at the depth of the BSR. It shows apositive deviation from its downward decrea-sing trend associated with the p-wave low-velo-city zone just below the BSR. At some locationsthis anomaly is stronger and seems to correlatewith enhanced reflection just below the BSR.We believe that this indicates the occurrence ofgas of higher concentrations underneath thehydrates. Further downward, the Vp/Vs-ratiocontinues to decrease to values of about 3 at adepth of 600 m below seafloor. The second gas-charged layer at about 500 m depth is notdetected by the shear waves. One of the pre-mier applications in offshore industry of recor-ding shear waves is to image through gasclouds. Whereas shear waves behave exemplaryfor the lower gas-charged layer in our case, theydo not so for the gas that occurs beneath the

BSR. Gas seems to be distributed heterogene-ously below the gas hydrates, as already indi-cated by the enhanced reflections. Gas hydratesact as a seal and continued accumulation of thetrapped gas possibly leads to local zones ofundercompaction and overpressure. Such over-pressure would reduce the effective stress andgrain coupling leading to low shear modulusand low shear-wave velocity.

Conclusion- Heterogeneous distribution of gas occurs

below the sealing gas hydrates. - Gas hydrate does not contribute to the

cementing of the sediments and its concentration seems to be low.

ReferencesAndreassen, K., Mienert, J., Bryn, P. and Singh,S. C., 2000. A double gas-hydrate related bot-tom simulating reflector at the Norwegian con-tinental margin. Annals Of The New YorkAcademy Of Sciences 912, 126-135.

Andreassen, K., Berteussen, K. A., Mienert, J.,Sognnes, H., Henneberg, K. and Langhammer,J., 2001. Investigating gas hydrates using seis-mic multi-component ocean bottom cable data.Extended abstract, EAGE 63rd conference &technical exhibition, Amsterdam, The Nether-lands, 11 – 15 June.

Bouriak, S., Vanneste, M. and Saoutkine, A.,2000. Inferred gas hydrates and clay diapirsnear the Storegga Slide on the southern edgeof the Voring Plateau, offshore Norway. MarineGeology 163(1-4), 125-148.

Guerin, G., Goldberg, D. and Meltser, A., 1999.Characterization of in situ elastic properties ofgas hydrate-bearing sediments on the BlakeRidge. Journal Of Geophysical Research-SolidEarth 104(B8), 17781-17795.

Mienert, J., Posewang, J. and Baumann, M., 1998.Gas hydrates along the northeastern AtlanticMargin; possible hydrate-bound margin instabilitiesand possible release of methane. GeologicalSociety Special Publications 137, 275-291.

Figure1:Location of the study area and data coverage.

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Gas hydrate formation and dissolution experiments in a pressure chamber

We started first experiments on the formationand dissolution of methane gas hydrates in adeep sea simulation chamber (APROACH,adaptive pressure ocean analysis chamber)constructed by the Technische UniversitätHamburg-Harburg (TUHH), Department ofOcean Engineering 1.

Up to now the kinetics of gas hydrate dissocia-tion was mainly studied in the context of tech-nical applications, where gas hydrates aredestabilised when temperature increases, pres-sure decreases, or when chemical agentsattack and destroy the hydrate matrix (SloanJr., 1998). The process of gas hydrate dissocia-tion through contact with methane-undersatu-rated bottom water, which controls abundance,distribution, and dissolution of gas hydratesoutcropping from the sea floor, has onlyrecently been studied in an in situ experimentalsetup, which used a remotely operated vehicletransporting methane gas hydrate piecesthrough the water column (Rehder et al. inprep.). Until now, there have been no attemptsto measure gas hydrate dissolution rates andkinetics under possibly changing salinity ormethane concentrations of the sea water inthe laboratory. The newly designed pressure chamber of theTUHH provides the possibility to study gashydrate formation and dissolution underalmost realistic conditions. The pressure chamberconsists of an pressure-stable cylindrical linerequipped with an inspection window for opti-cal observation, a base plate with split connec-tors, a crane, the pressure pump and a cryostat(Figure 1). Pressure (0–500 bar) and Tempe-rature (1–25 °C) are selectable and can bemonitored online with standard data

processing equipment. During first experi-ments we were able to synthesise methane gashydrate in salt water (Figure 2) and subse-quently watch its dissolution. The dissolutionrates of gas hydrate will be calculated fromhigh precision conductivity measurements,using an enhanced sensor (originally from aCTD-probe, K.U.M., Kiel). During gas hydrate formation in the inner reac-tion vessel ion exclusion is responsible for a sali-nity increase in the surrounding sea water, whe-reas dissolution leads to a salinity decrease.

Drews M. (1), Holscher B. (2), Gust G. (2), Wallmann K. (1)

(1) GEOMAR Research Centre for Marine Geosciences, Wischhofstrasse 1 - 3, 24148 Kiel, Germany

(2) Ocean Engineering 1, Technical University Hamburg-Harburg, 22305 Hamburg, Germany

Figure 1:Deep sea simulation pressure chamber constructed bythe Technische Universität Hamburg-Harburg,Department of Ocean Engineering 1.

32

ReferencesRehder, G., Kirby, S. H., Durham, W. B., Stern,L., Peltzer, E. T., Pinkston, J., and P. G. Brewer(in prep.): Dissolution rates of pure methanehydrate and carbon dioxide hydrate in under-saturated seawater at 1000 m depth.

Sloan, Jr., E., D. (1998): Physikal/chemical pro-perties of gas hydrates and application toworld margin stability and climate change. In:Gas Hydrates: Relevance to World MarginStability and Climate Change, Vol. 137 (ed. J.-P. Henriet and J. Mienert), pp. 31-50. Geolo-gical Society.

Figure 2:Methane gas hydrate formed at 1 °Cand 90 bar at the gas phase waterboundary in the inner reaction vesselof the pressure chamber.

We present first microbiological and geoche-mical results obtained during the METEOR cruise 52-1 from sediments at the Odessa andYalta mud volcanos in the Sorokin Through inthe northern Black Sea at water depths about1800–2100 m. The geochemical characteristicsof the sediment (anoxic and sulfidic conditions,gas hydrate occurrences 1 m below the seafloor) where bacterial mats associated with car-bonate crusts occur, is a strong indication thatthese mats are responsible for anaerobic metha-ne oxidation mediated by sulfate reduction.

At station 18-TGC, approximately 1.5 km eastof the Odessa mud volcano (44°21.01 N,35°09.28 E) in 1936 m water depth, we obtained a gravity core which contained gashydrates and bacterial mats attached to carbo-nate crusts. This core was studied in greatdetail with respect to geochemical analyses(pH, sulfide, sulfate, methane, alkalinity, andammonia concentrations in the pore water,Figure 1) and microbiological activity measure-ments.The boundary in approximately 20 cm depthbetween light grey hemipelagic mud and ablack sapropel layer consisted of a 2 cm thickcarbonate crust associated with a bacterial mat.The pores of the crust were filled with stiffgelatinous white to pink bacterial colonies. Thesulfate concentration decreased in a sharp gra-dient from bottom water values (17.6 mM) to 1–1.6 mM in about 20 cm sediment depth, wherecrust and mats were located. Likewise, sulfidedecreased from highest concentrations in thesurface layer (4 mM) in a steep gradient. Thisstrongly hints on intensive bacterial sulfate reduc-tion. As a consequence of anaerobic methaneoxidation, which is mediated by the sulfate reduc-

tion (CH4 + SO42– ¢HCO3

– + HS– + H2O), thehydrogen carbonate concentration and there-fore the total alkalinity shows highest values(16 mM) just above the crust. Carbonate precipi-tation is caused by the production of carbonatealkalinity during anaerobic methane oxidation(Ca2+ + 2HCO3

– ¢ CaCO3( ) + CO2 + H2O).High quantities of small gas hydrate pieceswere found in two strata. The dissociation ofgas hydrate during sampling becomes appa-rent by very high methane concentrations inthe whole core, and in particular in peak con-centrations in the same layers as the gas hydra-tes occurrences. Measured methane profilesare therefore largely artifacts and do not repre-sent in situ methane concentrations. The dissociation of gas hydrate during core retrie-val also leads to the dilution of pore watermeasured as a decrease of the chloride con-centration. Further, the very low temperatureof the sediment measured on deck (0.7 °C)compared to the in situ bottom water tempe-rature (9 °C) is a consequence of the endo-thermic dissociation reaction. At TV-grab station 8-TVG in 1874 m depth atthe south western flank of the Odessa mud vol-cano (44°22.97 N, 34°08.50 E) we could conti-nue the sampling of carbonate crusts and asso-ciated bacterial mats. The grabbed materialconsisted of dark grey hemipelagic mud andcrusts. A different type of bacterial mat, brow-nish to yellow and slimy, appeared when thesediment was retrieved on deck. Below thecarbonate crust sediment pieces showed acoating with a stiff mucus-like bacterial matbeing attached to the sediment fracture walls.This gave the idea of filled passages or chan-nels which released the slimy substance whentorn open. The sediment was characterised by

33

Microbiological and geochemical investigationsat gas hydrate sites in the Black Sea

Drews M. (1), Schmaljohann R. (2), Aloisi G. (1), Wallmann K. (1)

(1) GEOMAR Research Centre for Marine Geosciences, Wischhofstrasse 1 - 3, 24148 Kiel, Germany

(2) Institut für Meereskunde (IFM), University of Kiel, Düstenbrooker Weg 20, 24105 Kiel, Germany

¢

34

sulfide concentrations of 1.5 mM and ammoniaconcentrations of 80 µM. High sulfate reductionactivity was indicated by very low sulfate con-centrations (0.3–2.6 mM). The alkalinity reacheda very high value of 14 mM.

On the central mound of the Yalta collapsedmud volcano in 2124 m water depth at station59-TVG (44°14.54 N, 34°47.11 E) we foundimpressive 2 to 4 cm thick bacterial mats atta-ched to carbonate crusts, which resembled thethick mats discovered in shallower waterdepths (above the gas hydrate stability field)during the Professor Logachew cruise in sum-mer 2001, and which grow on carbonatechimneys where methane gas bubbles surgeinto the water column (GHOSTDABS project).

The bacterial mats discovered during our crui-se were probably of the same type Pimenov etal. (1997) described as coral-like structured,overgrowing aragonite crusts in water depthsof 150–190 m in the north western shelfmethane seep area in the Black Sea. Activitymeasurements combined with microscopic andradio isotopic investigations revealed anaerobicmethane oxidation.

ReferencePimenov, N. V., Rusanov, I. I., Poglazova, M. N.,Mityushina, L. L., Sorokin, D. Y., Khmelenina,V. N. and Trotsenko, Y. A. (1997): Bacterialmats on coral-like structures at methane seepsin the Black Sea. Microbiology, 66 (3): 354–428.

Figure 1:Pore water chemistry of station 18-TGC approximately 1.5 km east of the Black Sea Odessa mud volcano in1936 m water depth. The top bar marks the zone where carbonate crust and bacterial mat occurred, thetwo lower bars mark the main gas hydrate zones.

Figure 2:Bacterial mat grown on carbonatecrust pieces of up to 30 cm lengthwere found at station 59-TVG (Yalta mud volcano in the Black Sea).The 2 to 4 cm thick mats were of ayellow to orange or pink colour andconsisted of a stiff gelatinous fabric.

35

Authigenic Carbonates in a Cold SeepEnvironment: Sensitive Recorders of RapidAnoxia and Sealevel Changes Determined byU- and Th-isotope Measurements (LOTUS)

Uranium (U) and Thorium (Th) concentrationsand activity ratios (δ234U; 230Th/234U) are precisegeochronometer and sensitive recorders of theredox conditions at submarine seeps of hydro-carbon-rich fluids at Hydrate Ridge, off thecoast of Oregon ('cold seeps'). The low U con-centrations but relatively high δ234U values ofgas hydrate carbonates reflect sedimentarypore water indicating that they were formedunder anoxic conditions below or at the sedi-mentary surface. Their (230Th/ 234U)-ages span atime interval from 0.82 to 6.34 ka and clusteraround 1.24 and 4.71 ka. This is interpreted asto reflect time intervals of intense CH4 flux andmicrobiological activity as well as gas hydrateformation.In contrast, chemoherm carbonates precipitatefrom marine bottom water. However, theirδ234U-ratios as well as the δ234U-ratios of thebottom water are enriched in 234U relative tonormal seawater. Mass balance calculationsreveal that this enrichment reflects a contribu-tion of about 10 % of U from sedimentarypore water to the bottom water and the chemoherm carbonates, respectively.234U/230Th ages of chemoherm carbonates (e.g.South East Knoll) vary in between 7.33 and267.72 ka and tend to correspond to timeintervals of low sealevel at glacial climatic stages (2, 4, 6, 8) and interstadials (7d). Latterobservation is confirmed by the measurementof stable oxygen isotopes (δ18O) which tend tobe enriched in the heavy isotope as it is expec-ted for carbonate formation during low sea-level positions. Following this observation, wepropose that long-term fluctuations of fluid

flow rates from hydrocarbon seepages arecontrolled by the pressure difference betweenthe seawater column and the plumbing systembelow the seepages. When sealevel is relatively high (during warm climatic stages)the hydraulic pressure of the water columnmay exceed the pressure of the plumbingsystem below the cold seeps. Then, no fluidflow occurs at cold seep areas. In contrast,when sealevel is relatively low the hydraulicpressure of the plumbing system may exceedthe pressure of the water column. Then, fluidflow occurs and triggers chemoherm carbona-te formation.

Eisenhauer A., Teichert B.M.A., Bohrmann G., Liebetrau V., Linke P.

GEOMAR, Forschungszentrum für Marine Geowissenschaften, Wischhofstr. 1-3, 24148 Kiel, Germany

36

Experimental determination of physical andphysico-chemical properties of gas hydrate-bearing sediments (Project 555A - Overview)

The overall objective of the project is to achie-ve a better understanding of the thermodyna-mic and kinetic behavior of mixed gas hydratesystems and the physical properties of gashydrate-bearing sediments by means of aninterdisciplinary research program combininggeophysical, mineralogical, geochemical, andcrystallographical approaches.An experimental program has been started tosimulate natural conditions of hydrate forma-tion. The expected results will allow more reli-able evaluation of methane energy resources,provide an improved basis for calibrating phy-sical properties which can be estimated in situ,and also provide data for numerical modellingof reservoir dynamics. A better knowledge ofthe stability of pure (CH4, CO2, N2) and mixedclathrates in the system CH4-CO2-N2-H2S-H2O isnecessary in order to reach the goals of thisproject.The detailed objectives are:1) To optimise and refine the newly-installed

gas hydrate-sediment experimental appara-tus for synthesis of natural gas hydrates ofthe structure type ”sI” in porous media.

2) To determine the influence of sediment structure on the formation and dissociationof gas hydrates as well as on their textureand distribution.

3) To determine seismic velocities and electricalproperties of sediments as a function of gashydrate content, composition and structure.

4) To determine how texture, distribution andgrain size of gas hydrate bearing sedimentscontrol hydraulic permeability.

5) To determine physical and thermodynamic properties of mixed clathrates in the systemCH4-CO2-N2-H2S-H2O and the influence of

gas fractionation on the formation ofmethane hydrates.

Hydrate-sediment experimental apparatus;low-temperature XRD sample chamberThe experimental apparatus was first appliedto the synthesis of gas hydrates in the absenceof a sedimentary matrix. The crystallization ofhydrates from aqueous fluid with dissolvedmethane required strong undercooling, andthe rate of reaction was much lower thanexpected and described in the literature. Toavoid these problems we developed an alter-native procedure whereby fine ice crystalswere slowly heated to the melting point in amethane atmosphere (p>100 bar). Underthese conditions, the reaction

5.75H2O(solid) + CH4(gas) ¢ CH4 • 5.75H2O

ran to completion within about one week. Thepure methane hydrates was used to calibrate abig volume calorimeter and the low-tempera-ture X-ray diffraction apparatus.

Synthetic hydrate-bearing "sandstone" ofknown composition was prepared by compres-sing mixtures of powdered methane hydratewith ice and sand in a cold methane pressuri-zed piston-cylinder cell. This material was usedto test the FLECAS (Field Laboratory Experi-mental Core Analysis System) which was deve-loped for the project "In-situ Gas HydrateLaboratory – Mallik Research Well". In addition, we continued with theoreticalmodelling of physical properties of hydratebearing sediments.

Erzinger J. (co-ordinator), Spangenberg E., Schicks J., Naumann R., Lüders V., Möller P., Kukowski N.

GeoForschungsZentrum Potsdam, Telegrafenberg, 14473 Potsdam, Germany

37

Technical details of the experiments and firstresults will be given as poster presentations(#20 and #22) by Kulenkampff, Spangenberg,Naumann and Spangenberg, Kulenkampff,respectively (for details see contributions in thisvolume).

The structural studies required the construc-tion of a special low-temperature X-ray diffraction sample chamber, which was com-missioned at the start of the project and delivered in the summer of 2001. Initial techni-cal problems with the controller unit and soft-ware were overcome, and an operational pro-blem of ice building up on the sample holdersduring test runs at -100°C was solved by flushing the chamber with cooled dry gaseousnitrogen. After these modifications, the firstsuccessful tests have shown that we can per-form crystal structure analysis of gas hydratesusing this comparatively simple and cost-effec-tive equipment.

Determining p-T-x phase relations of pureand mixed gas hydratesA specially designed cooling stage mounted ona petrographic microscope was set up in 2000which allows observation of hydrate formationand dissociation in transmitted and reflectedlight under controlled conditions of tempera-ture, pressure and gas composition. This firstprototype was able to deliver a temperatureprecision of ± 2°C over the range of -18 to+80°C. A second stage was built in 2001which has a greatly improved temperature pre-cision of ± 0.1°C in the range -27 to +80°C,but allows observation only in reflected light.Both stages can be operated with a Ramanspectrometer, as well. Phase diagrams for themethane-water system have been determinedusing this equipment and these show excellentagreement with literature data. The first resultsof the actual measurements on the system CH4 – CO2 – H2O will be presented orally bySchicks, Lüders, and Möller (for details seecontribution in this volume).

38

The role of gas hydrates in the course of rapidclimate changes - Isotopic studies on methanein polar ice cores

SummaryFocus of this project is the identification of thesources responsible for changes in the atmos-pheric methane concentration during rapid cli-mate changes in the past and here especiallythe role of a potential destabilization ofmethane hydrates. To this end isotopic measu-rements of methane will be performed on airsamples extracted from a northern Greenlandice core covering the complete last glacial cycleusing a new gas chromatography mass spec-trometry method. The development of thismethod enables for the first time to performhigh precision carbon and hydrogen isotopicmeasurements on very small ice core air sam-ples and using the isotopic signature of metha-ne to constrain the sources responsible forpaleoclimatic methane variations in the atmos-phere.

BackgroundBubble enclosures in polar ice cores representthe only direct atmospheric archive for thereconstruction of paleoatmospheric variationsin methane concentrations over up to the last500,000 years. Previous ice core studies sho-wed an extraordinary close coupling of atmos-pheric methane concentrations and isotopetemperatures as reconstructed from Greenlandice cores (Fig. 1). The long-term trend inmethane shows an increase from concentra-tions below 400 ppbv during the last ice ageup to a level of 700 ppbv during warm climateperiods [Raynaud, 1993]. Starting at about1750 AD a clear anthropogenic increase toconcentrations of more than 1700 ppbv couldbe detected [Etheridge et al., 1998]. In addi-

tion to these long-term changes very strongincreases in the atmospheric methane concen-tration of about 200 ppbv occurring over a fewdecades to centuries were found in parallel torapid climate variations in the northern hemis-phere (Dansgaard-Oeschger events, YoungerDryas) during the last glacial [Chappellaz et al.,1993]. The contributions of different sources to thesechanges in atmospheric methane concentra-tions and here especially the role of gas hydra-tes are not unambiguously known so far. Inthis respect a climate induced destabilizationof marine methane hydrate stocks as well asthe release of methane bound in permafrostregions could represent a major player duringrapid climate warming events. A first approachto distinguish different geographic methanesource regions is based on the interpretation ofthe interhemispheric gradient in methane con-centration (as determined on Greenland and

Fischer H., Richter K.-U.

Alfred-Wegener-Institute for Polar and Marine Research, Columbusstrasse, 27568 Bremerhaven, Germany,

hufischer@awi-bremerhaven.de

Figure 1: Isotope temperature and methane profile of the GRIP ice core, central Greenland

39

Antarctic ice cores). The results of this app-roach point to a strong source in middle andhigh northern latitudes at the beginning of theHolocene, as expected for a methane releasefrom thawing permafrost [Chappellaz et al.,1997]. However, in the course of rapid climatevariations such a gradient can not reliably bedetermined.

Here, the isotopic composition of methanerepresents an unique tool to distinguish diffe-rent methane sources and to quantify the glo-bal methane budget in more detail (Fig. 2). Thecarbon isotopic composition enables to distin-guish thermogenically and recently bacteriallyproduced methane. Furthermore, the hydro-gen isotopic composition allows for a distinc-tion of different bacterial pathways, hence themilieu in which the bacterial methane produc-tion takes place (marine vs. terrestrial) (Fig. 2).In addition, the reaction of methane with OHradicals, representing the major sink of metha-ne in the atmosphere, results in an enrichmentof the heavier methane isotopes in the atmos-phere. Thus, the reconstruction of paleoclima-tic changes in the isotopic composition ofatmospheric methane can contribute distincti-vely to assign the relevant source processes tothe observed concentration changes duringDansgaard-Oeschger events and the last glacial/interglacial transition.

ObjectivesIn order to answer the question of the origin ofvariations in atmospheric methane concentra-tions during rapid climate changes, carbon(and in a second step also hydrogen) isotopicmeasurements on methane in ice core air bubbles will be performed on the North-GRIPice core, drilled in the years 1998-2001 in nor-thern Greenland. The measurements will focuson investigations on selected Dansgaard-Oeschger events, the Holocene/Pleistocenetransition (Younger Dryas, Bølling-Allerød oscillation), the last glaciation and for valida-tion of the method on recent ice. Due to thevery large sample size required for such analy-ses so far (25 kg of ice), previously publishedvalues of the methane isotopic composition

from ice cores are restricted to a pilot study byCraig et al. [1988]. To lower the detection limitsignificantly we are currently developing a newgas chromatography isotope ratio monitoringmass spectrometry (GCirmMS) method[Merritt et al., 1995] both for δ13C and δD inCH4. This method reduces the necessary sam-ple size to 10-50 ml STP (equivalent to 100-500 g of ice). Test measurements of δ13CH4 in20ml air samples using this method showed areproducibility of 0.1‰. For the analyses of icecore air samples a melt extraction is current-ly developed, which warrants the completeextraction of air from bubble enclosures inthe ice.

In a second step an online preparation methodfor hydrogen in methane will be established. Insummary, after completion of the technicaldevelopments a method for direct δ

13C and δD

analyses on methane in very small air sample isavailable for the first time, which will also allowto perform comparable isotopic studies in othergeoscientific fields.

Figure 2: Isotopic signature of different methane sourcescompared to the atmosphere [Whiticar, 1993]

40

ReferencesBlunier, T. and E.J. Brook, Timing of millenial-scale climate change in Antarctica and Green-land during the last glacial period, Science,291, 109-112, 2001.

Chappellaz, J., T. Blunier, S. Kints, A.Dällenbach, J.-M. Barnola, J. Schwander, D.Raynaud, and B. Stauffer, Changes in theatmospheric CH4 gradient betweenGreenland and Antarctica during theHolocene, Journal of Geophysical Research,102 (13), 15987-15997, 1997.

Chappellaz, J., T. Blunier, D. Raynaud, J.M.Barnola, J. Schwander, and B. Stauffer,Synchronous changes in atmospheric CH4 andGreenland climate between 40 and 8 kyr BP,Nature, 366, 443-445, 1993.

Craig, H., C.C. Chou, J.A. Welhan, C.M.Stevens, and A. Engelkemeir, The isotopiccomposition of methane in polar ice cores,Science, 242, 1535-1539, 1988.

Etheridge, D.M., L.P. Steele, R.J. Francey, andR.L. Langenfelds, Atmospheric methane bet-ween 1000 A.D. and present: Evidence ofanthropogenic emissions and climatic variabi-lity, Journal of Geophysical Research, 103(13), 15979-15993, 1998.

Merritt, D.A., Hayes, J. M., Des Marais, D. J.,Carbon isotopic analysis of atmosphericmethane by isotope-ratio-monitoring gaschromatography-mass spectrometry, Journalof Geophyiscal Research, 100 (D1), 1317--1326, 1995.

Raynaud, D., Jouzel, J., Barnola, J. M.,Chappellaz, J., Delmas, R. J., Lorius, C., Theice core record of greenhouse gases, Science,259, 926--934, 1993.

Whiticar, M.J., Stable isotopes and global bud-gets, in Atmospheric methane: sources, sinks,and role in global change, edited by M.A.K.Khalil, pp. 138-167, Springer, Berlin, 1993.

Two different tools are designed and testedwithin this INGGAS subproject:

1. a 6m long heat flow probe to expand measu-rement capabilities from deep sea environmentsto shallow water (continental margins) in ordermeasure reliable sediment temperature gra-dients in the presence of bottom water tempe-rature variations2. a pore pressure tool to measure in situ porepressures in sediments in order to quantify fluidflow. This second tool is split into two units: a)the data acquisition unit and b) an autonomous-ly operating data transmission buoy.

1 Heat flow probeThe new heat probe is capable to measure tem-perature gradients and in situ thermal conducti-vity in sediments to determine terrestrial heat

flow. The large penetration depth of 6m, twice asdeep as normally used instruments is necessary toget reliable results in water depth of less than2000m where varying bottom water tempera-tures create transient temperature disturban-ces in the subsurface. This is very often thecase for heat flow surveys over gas-hydratebearing sediments at continental margins. Themechanical design of the probe follows theviolin bow concept and is adapted in size andmaterial strength to the desired maximumpenetration depth. Numerical modeling of thedimensions of sensor string and strength mem-ber assisted in the final design. The data acqui-sition in the instrument is normally under real-time control from a deck unit on board theresearch vessel but can also be operated in acompletely autonomous way if no suitablecable is available on board.

Data acquisition unit (in Data logger forheat probe at seafloor) • Signal conditioning of analogue temperature signal

• A/D conversion with 22 bit resolution• Data storage• Control of heat pulse for in situ thermal conductivity measurement• Data acquisition and storage of penetration monitoring sensors

(pressure, tilt, acceleration, altimeter)• Real-time communication with deck unit through coax deep sea cable• Temperature range of –2 to 70 °C• Temperature resolution of < 1mK from –2 ° to 12 °C• Battery and storage capacity allow continuous operation for 3 days• Operational up to 6 km water depth

Deck unit (on board PC for:research vessel) • Data capture and storage on hard disk

• Control of the instrument at the seafloor• Communication with the instrument at the seafloor through coax

deep sea cable• Real-time graphical display of data

41

INGGAS-Flux: New tools for energy and fluid-flux: pore pressure and thermal gradient probes

Gennerich H.-H., Grevemeyer I., Kaul N., Villinger H.

Fachbereich Geowissenschaften, Universität Bremen, Postfach 330 440, 28213 Bremen, Germany

The data acquisition system including the com-munication package is designed and built byan industry partner according to our specifica-tions. The complete mechanical system isshown in Figure 1. A first sea trial will takeplace during M54/2 off Costa Rica inAugust/September 2002.

2 Pore pressure toolThe goal is to detect vertical fluid flow withinseafloor sediments with rates as low as 1mm/a. This will be achieved by measuring porepressures in the sediments at various depthsfor a maximum period of two month with aminimal time resolution of 10 minutes tomonitor tidal and other low frequency effects.

We decided to employ one differential pressu-re transducer and three subsurface pressureports using a hydaulic multiplexer. Operationof the hydraulic multiplexer has been tested inthe laboratory and under deep ocean pressurecondition in a pressure chamber as well. Afterfree-falling to the seafloor the instrumentrecords pressures over a preset time windowand the data are transfered to the satellitecommunication unit. This unit will surface afterthe end of the measurement period and sendthe data to shore via an IRIDIUM satellite link.The complete system is designed as expenda-ble system to save additional ship time cost forrecovery of the data. A sketch of the systemdesign is shown in Figure 2.

42

Data acquisition unit Data logger for(pore pressure • Signal conditioning of analogue differential pressure signalmeasurement) • A/D conversion with 22 bit resolution

• Data storage• Data acquisition and storage of environmental

parameters (tilt, temperature)

• Data transmission to satellite communication unit• Battery and storage capacity allow continuous

operation for 2 months• Operational up to 6 km water depth

Satellite communication • Storage of pressure and environmental dataunit • Timing release

• Data compression• Transmission of complete data set through IRIDIUM

satellite link

The satellite communication system is desig-ned and built by an industry partner accordingto our specifications. The complete mechanicalsystem is shown in Figure 2. A first sea trial willtake place at the end of March 2002 in theBaltic Sea. A second test is scheduled forOctober 2002.

43

Figure 1: New heat probe with totallength of 8,1 m and aminimum total weight ofca. 900kg.

Figure 2: Sketch of the expendable differentialpore pressure probe. The data transmission unit is a self-containedsatellite data transmission link.

44

Quantification of dissolved and free methaneat gas hydrate associated cold vents: The useof lander and ship mounted hydro acousticsystems and methane sensors

Methane hydrates are an important carbonreservoir in the marine environment that areformed from the advection of methane andH2S rich fluids through sediments. Methanehydrates form only when very high concen-trations of methane, most likely in the formof free gas, are present at high pressures andlow temperatures. Thus gas hydrates are closely linked to free gas emissions from theseafloor into the water column and possiblyinto the atmosphere, and high methane con-centrations are found in the water columnnear hydrate deposits. Important mecha-nisms that influence the carbon cycle at coldvents are the biogenic anaerobic oxidation ofmethane and the precipitation of carbonate.Similar reactions occur in bacterial mats atthe seafloor or within the water column andreduce the methane flux from cold vents.However, free gas emission in form of bubblestreams from the seafloor is suggested to beof major importance for the vertical transportof methane, which may impact regional andglobal carbon cycles. The amount and peri-odicity of free gas emissions cannot be inve-stigated by the classical water sample andGC-analyse procedure, which is used to inve-stigate the distribution and fate of dissolvedmethane.

Gas bubbles such as swim bladders of fishare recognized by hydro acoustic methods,and these bubbles can by quantified. WithinSubproject 2 of the LOTUS Project, we areredesigning the PARASOUND hydro acoustic

system (installed on RV SONNE, RV METEORand RV POLARSTERN) in order to detect coldvents where gas bubbles escape from theseafloor. In a second step we plan to quanti-fy the gas amount recorded by the 18 kHzsignal of the PARASOUND system. Russianscientists have successfully used single beamecho sounders for hydro-acoustic bubbledetection in the Black Sea and the Sea ofOkhotsk. To obtain an accurate estimate ofthe volume of gas emitted, a sonar-like hydroacoustic swath system, Gas-Quant, has beendeveloped in cooperation with ELAC-Nautik.This system will be mounted on a lander anddeployed near known gas-emission sites atthe Hydrate Ridge (Oregon) for the purposeof recording the distribution of bubble streams,their periodicity and the gas amount.

In addition to 'bubble-detection', the distri-bution of dissolved methane in the watercolumn will be investigated by classical geo-chemical methods and with methane sensors(METS) build by CAPSUM. The sensor hasbeen improved and redesigned for long-termdeployment on moorings. Water samples willbe analysed for the carbon isotopic signal ofthe dissolved methane and other carbon spe-cies with a new mass spectrometer. This willhelp to distinguish between different metha-ne sources and to investigate methane oxida-tion rates in the water column.

Greinert J. (1), Keir R. (1), Spieß V. (2)

(1) GEOMAR Research Center for marine Geosciences Kiel, Germany, jgreiner@geomar.de

(2) University of Bremen, Germany

45

Both the hydro-acoustic and geochemicalinvestigations will provide strongly neededinformation about the inventory and oxida-tion of methane in the water column inregions containing gas hydrates.

Figure 1: The METS mooring system during a test onboard RV ALKOR in October 2001.

Figure 2:Screen shot of 3 gas bubble flares recorded with the modified PARASOUND system onboard RV METEOR January 2002.

46

Slope Stability and Land Slides in the DeepSea: Influence Parameter Gas Hydrates (GASSTAB)

Decomposition of gas hydrates is thought tobe a major cause for the instability of submarineslopes and deep sea floor. The project GAS-STAB is focused on the influence of gas hydra-tes on slope and ground failures from amechanical point of view. The aim of our inve-stigation has been to establish a base for thetheoretical prediction of submarine failuremechanisms.

Possible failure mechanisms of slopes contai-ning gas hydrates were postulated by McIver[1982]. To verify these mechanisms we haveanalytically computed a discrete model; at alater date we intend to calculate numericalsimulations. These calculations must be tightlyinterconnected with the mechanical behaviorof hydrate bearing sediments to understandthe processes governing slope and floor failure.Because there is no or only little soil mechani-cal data available, a laboratory Gas HydrateTest System (GTS) for different soil mechanicalexperiments is under construction.

Sediment samples from the Ocean DrillingProgram (ODP) leg 164 were investigated togain basic data for the mentioned models andto compose an artificial sediment for the labo-ratory experiments. In the following the pro-gress of the three project parts of GASSTAB isdescribed.

Numerical ModelingMcIver's model shows a large block of cemen-ted sediment, breaking off and sliding down-slope on a layer of liquefied sediment (Fig. 1a).

His scenario was adapted to create a soilmechanical model which is based on two simplifications (Fig. 1b). First the sliding planeshows neither friction nor cohesion andsecond the model is a 2D profile, assumingsymmetrical load distributions.

The results of stability calculations are shownin the picture below. Fig. 2a shows the factorof stability (η = Qmax /Qin situ ) versus the slopeangle (α) and the inclination of destabilizedgas hydrate layer (β). The stability of the slopeis documented by η >1, left to the thick line

Grupe B. (1), Kreiter S. (1), Feeser V. (2), Hoffmann K. (2), Becker H.J. (2), Savidis S. (3), Schupp J. (3)

(1) Technische Universität Berlin, Institut für Technischen Umweltschutz, Germany

(2) Christian-Albrechts-Universität zu Kiel, Institut für Geowissenschaften, Germany

(3) Technische Universität Berlin, Institut für Bauingenieurwesen, Germany

Figure 1: (a) above, Model after McIver, (b) below, Transfer of Fig.1a into a soil mechanical model.

47

describing the critical state. Fig. 2b shows thevariation of the critical state line for differentfriction angles (the thick line is the same as inFig. 2a). The gray shaded area correspondswith the in situ observed slope and slidingplane angles. Similar relations were found byvarying the cohesion and the length of the sli-ding plane, respectively.

A verification of the analytical results is in pro-gress using numerical simulations with finiteelements on different platforms. Furthermoredynamical tests are planed to include the trig-gering phase of the failure mechanism.

Soil Mechanical Material BehaviorThe strength of sediments in natural deposits ismainly controlled by the stress history whichthey have undergone as well as by the actualstress and pressure regime within their grain ske-leton and their void. Stress history of marinesediments which follow hydrate formation anddecomposition has neither been experimental-ly nor theoretically investigated so far.

GASSTAB will make a first contribution bothexperimentally and theoretically to understandand quantify stress history and current stressand pressure states of sediment, gas andhydrate systems.

For experimental investigation of these com-plex interrelations a special Gas Hydrate TestSystem is under construction. GTS will be anoedometer type device. It will enable the formation and decomposition of gas hydratesunder real deep sea conditions and simultane-ously allow the measurement of stress – strainreaction within the sediment. Controlledboundary conditions are: sediment volume andstresses, pore water pressure, gas pressure,temperature and spatial distribution of gashydrate.

For the detailed design and the construction ofGTS a set of preliminary tests were inevitablynecessary. Physicochemically preliminary testsfor the formation of gas hydrates were performed with tetrahydrofurane (THF) andpropane. Additionally equipment for highpressure tests with methane has just been justcompleted. The observed effect of the water’smetastable cluster states on the kinetics of gashydrate formation led to a redesign of the peripheral pressure devices of the GTS.

Further preliminary tests were conducted inorder to find a suitable method to measure thespatial distribution of hydrates within the sample chamber. Ultrasonic propagation, electrical resistance and temperature weremeasured. As a result electrical resistance measurements were selected for deploymentin GTS. In co-operation with Kiel University ofApplied Sciences an electrical resistance tomography will be developed, to detect thespatial distribution of the gas hydrates in thesediment.

Preliminary soil mechanical tests are in pro-gress, to synchronize optimize the design anddimensioning of the electrical sensor tech-nology and to develop GTS’s controlling

Figure 2: (a) above, Slope stability versus inclinations,(b) below, Nomogram of critical state lines for differentfriction angles.

48

algorithms. For this purpose an oedometricdevice was re-equipped. First tests with THFhydrates in sands have been started.

The theoretical approach is based on a numericmodelling of the mechanical sediment - gashydrate interaction. With the aid of DEM(Distinct Element Method) a virtual testing toolis being developed to simulate gas hydrate for-mation and decomposition. This provides theadvantage to run virtual tests under variousboundary conditions considerably faster thanreal tests. First trials have been carried out to simulate the growth of hydratecrystals in the pore space of sediments.

Actual Petrographic Sediment ConditionsThe assessment of gas hydrate containing sediments requires knowledge of the sedimen-tological, petrographical and soil mechanicalindex properties. As for the experiments withGTS larger amounts of sediment are required,an artificial sediment had to be created. Thefollowing two main questions had to be ans-wered: are there special properties allowinghydrate to grow and what will the artificialsediment’s composition be? For this purpose96 sediment samples from ODP leg 164 wereinvestigated. The samples, from zones above,within and below gas hydrate containing layers were studied (by SEM analysis) withregard to their grain size distribution, claymineral composition and microtexture. Thevalues of certain additional parameters likewater content, bulk density and shear strengthhad to be gained from literature, as significantchanges to the original state of the sampleshad taken place.

The sediments can be generally classified assilty clays or clayey silts with little variation intheir sand contents. In most of the samplestaken from one and the same sediment layerthe grain size changed significantly. So thesediment is homogeneous on the large scale (> 10 cm) but highly variable on the smallscale. No grain size differences between sedi-ments above, within and below gas hydratecontaining layers could be found.

SEM investigations of 35 different sedimentsamples have shown that they are mainly composed of flaky shaped, small sized clayminerals, calcareous nannofossils, foraminifers,diatoms and small amounts of grains. Thenumber of open pores within the sedimentstabilized by biogenitic shells decreases withdepth below the sediment surface. Sedimentsfrom the gas hydrate bearing zones did notshow more open pores than layers withouthydrates.

X-ray investigations of 10 samples (fraction < 2µm) from different sediment depths (50 m -700 m) have shown that within the whole sec-tion illite (50 wt%) is the dominating mineralfollowed by kaolinite (40 wt%) and chlorite(10 wt%).

Because we cannot be sure that the sedimentsamples we investigated ever contained gashydrates, different artificial sediments, takinginto account the determined small scale variability, have been composed. Clay mineralsfrom a Kulm clay stone and a kaoline depositwere mixed with varying amounts of pure bio-genetic components for the coarser fraction.These artificial sediments will be used for all future GASSTAB soil mechanical tests. On theother hand this variation of the composition hasthe advantage of investigating the effects ofgrain size, clay mineral content and different bio-genetic components on gas hydrate formation.

LiteratureMcIver, R. D. , Role of naturally occurring gashydrates in sediment transport. AmericanAssociation of Petroleum Geologists Bulletin,66, 789-792, 1982

Proceedings of the Ocean Drilling Program,Vol. 164, Scientific Results, 2000

Proceedings of the Ocean Drilling Program,Vol. 164, Initial Reports, 1996

49

An in-situ laboratory array for biogeochemicalprocesses under deep sea conditions with andwithout fluid venting

Investigations of temporal and spatial variabili-ty of composition and decomposition proces-ses of natural gas hydrates require undisturbedenvironmental conditions. In-situ experimentswhere gas hydrates remain embedded in theiroriginal sedimentary matrix provide adequateconditions for such undisturbed experimentsand permit to investigate physical, chemicaland biogeochemical mechanisms related tocomposition and decomposition of surface-near gas hydrates. Within this project (LOTUS,TP 1) an in-situ laboratory array for biogeoche-mical processes under deep sea conditionswith and without fluid venting has been deve-loped and successfully tested .

Main components of the laboratory array aretwo benthic and one fluid-column laborato-ries: the Fluid Flux Observatory, the Bio-geochemical Observatory and the Particle Flux(Carbon Flow) Observatory. These Ob-servatories work either independently or syn-chronously to complement each other in theirresearch tasks.

Major objective of the Fluid Flux Observatory(FLUFO) is to identify and quantify the effectivedischarge rates related to composition anddecomposition of gas hydrates and to discernthe impact of environmental parameters suchas temperature, pressure, permeability andnear bottom currents.

Fluid flow released from sediments containinggas hydrates were found already during the90ies (e.g. Carson et al., 1990 / Linke et al.,1999) from long term deployments of ventbarrels. These measurements indicated a

correlation between tidal signal and fluid flowfrom or into the sediment and represented animportant first step towards the identificationof dynamical processes associated with gashydrate stability. Subsequently executed laboratory experiments revealed additionalinfluences on the measurement by lateral flowand the permeability of the sediment.Advances beyond currently used measuringsystems required to consider these effects.Further desirable steps for improvements weredetermination of the direction of the fluid flow(in- or outflow) and the quantification of theratio between vented gas and water. To meetthese goals, our group developed a completelynew flow measurement system and, in addi-tion, established a laboratory calibration facility for FLUFO systems under simultaneousexposure to horizontal and vertical flow.

The new designed measurement system - reduces the effects from lateral flow by

selection of a suitable geometry- reduces the effects from lateral flow by

preventing leakage out of the device- quantifies the ratio gas/water in the

venting fluid - quantifies the permeability of the sediment- determines the direction of vertical flow (in

or out)- increases the sensitivity and dynamic range

of discharged flow volume

These advancements are linked to a new basicprocedure for the measurement of fluiddischarge based on a tracer method. An integral part of the development of thenew flow measurement system were extensive

Gubsch S., Viergutz T., Gust G., Müller V., Holscher B.

Ocean Engineering 1, Technical University Hamburg-Harburg, 22305 Hamburg, Germany

50

numerical simulation for hydrodynamic perfor-mance of the fluid-flux-measuring system.Especially the pressure dependence of theinteraction between the measuring system and the fluid out- or inflow to the bottom wasinvestigated as a decision criterion for theselection of an optimised performance to mea-sure very slow flow velocities in an opensystem. For assessing the influence of changedboundary conditions between calibration anddeployment of the system, either the labora-tory or typical in-situ boundary conditions aretaken into account. A data reduction codeexist which will be used to evaluate measureddata of the Ortega I cruise.

With the Biogeochemical Observatory (BIGO),the temporal variability of the biologically facilitated turnover in the sediment and fluxesacross the sediment water interface are studied at time scales ranging from days toweeks. For realising adequate hydrodynamicconditions inside the chamber the flow velocityis measured by a sensor and transmitted to acalibrated stirring device which generates andmaintains equal hydrodynamic conditions. Thetime series of chamber bottom stress can alter-natively be artificially maintained, continuouslyadjusted to changes of environmental flowparameters, or freely programmed by a pre-selected look-up table. With this laboratory,chemical and biological in-situ experiments areexecuted independently of vertical fluidrelease.

The hydrodynamic conditions at the confinedsediment-water interface are realised by a two-parameter control of the stirring device. Its out-standing feature is a spatially homogeneousbottom stress with steady or variable timehistory inside the chamber. The features of thispatented chamber have been improved furtherby providing - an energetically optimised version of the in

situ stirring-and-pump system, - optimised experimental space inside the

chamber by changing the geometry of thestirrer while maintaining spatially homo-geneous bottom stress. This change resulted

in experimentally accessible sediment surface from the chamber lid of more than500 cm2.

The main features of the hydrodynamic perfor-mance of both systems FLUFO and BIGO weresuccessfully tested both in laboratory experi-ments and under real conditions during thecruise ALKOR 192 at water depths of 329 and315 meter. Biogeochemical processes at thesediment-water interface are not only affectedby the hydrodynamic conditions but by thepresence of particulate matter as well. Sourcesare either sinking particles from surface andpelagic regions, or resuspended particlesadvected with the flow. The Particle FluxObservatory (PAFLO) provides a means toquantify this mass flux and associated carbon/nutrient flux. It is intended to quantify with thisobservatory the extent to which biomatsobserved to thrive at methane release areas aredependent on either or all of the stimuli ofinterfacial hydrodynamics, the release of constituents from the venting fluid and thesettling of particulate matter from above andupstream.

This project utilises a new patented trappingprotocol for particulate matter in connectionwith PAFLO where the in-situ sinking-particleflux is obtained from the collection rates ofcylinders of different geometries which form amultiplett of simultaneously deployed traps.The mass collected in these traps follow independent accumulation equations per traptype (developed in another research project)and are used to establish an equation systemwhich is solved for the concentration of sin-king particle sub groups involved. Multipliedwith the sinking velocities the fluxes of theseparticle sub groups are obtained (Gust andKozerski, 2000).

The three observatories have been developedand tested to a level that the scientific missionsto be met during research cruise Ortega 1 inhydrate-bearing sediment zones can be appro-ached with novel, advanced and tested gear.Details of the design features, equations and

51

array performance in the Baltic and theAtlantic are presented.

ReferencesCarson B., Suess E., Strasser J.C. (1990) FluidFlow and Mass Flux Determinations at VentSites on the Cascadia Margin AccretionaryPrism. J. Geophys. Res. 95/B6: 8891-8897.

Gust, G. and Kozerski, H.P.: In-situ sinking-par-ticle fluxes from collection rates of cylindricaltraps. Marine Ecology Progress Series, 208(2000), pp. 93 – 106.

Linke, P., O. Pfannkuche, M. E. Torres, R. Collier,U. Witte, J. McManus, D. E. Hammond, K. M.Brown, M. D. Tryon, K. Nakamura: Variability ofbenthic flux and discharge rates at vent sitesdetermined by in situ instruments. Eos. Trans.AGU, 80(46), 1999, Fall Meet. Suppl., F509.

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Gas hydrate dynamics – Modelling hydrateformation in near surface sediments

Massive gas hydrate layers are formed in thenear-surface sediments of the Cascadia margin. A nearly undissociated piece of hydratecould be recovered at the base of a gravity corer(i.e. in 120 cm sediment depth) on the southern summit of Hydrate Ridge. As a resultof salt exclusion during the methane hydrateformation, the associated pore waters show ahighly elevated chloride concentration of 809 mM, compared to the normal values of543 mM. Corresponding δ

18O and δD profiles

indicate that the chloride anomaly certainlyoriginates from hydrate formation.

From this first field observation of a positive Cl

–anomaly, we calculate comparatively high

hydrate formation rates (0.5-1.2 mol cm –2 a –1)[1], also revealing a highly dynamic system.Our simple non-steady state diffusion-advec-tion model also constrains the rate of fluidflow at the Cascadia accretionary margin to be110-250 cm a –1 [1]. These rates are orders ofmagnitude higher than rates previously repor-ted for deep-seated sedimentary hydrates(Blake Ridge, ODP site 997) [2].Furthermore, the calculated flux of methanefrom below that is needed to build up thenecessary amount of methane hydrate whichcauses the observed chloride enrichmentstrongly suggests that most of the gas hydratemust have been formed from ascendingmethane gas bubbles rather than solely fromCH4 dissolved in the pore water.

References[1] M. Haeckel, E. Suess, K. Wallmann and D.Rickert, Rising methane gas-bubbles form massive hydrate layers at the seafloor, Geology,submitted.

[2] P.K. Egeberg, G.R. Dickens (1999), Thermo-dynamic and pore water halogen constraints ongas hydrate distribution at ODP Site 997 (BlakeRidge), Chemical Geology 153, 53-79.

Haeckel M., Suess E., Wallmann K., Rickert D.

GEOMAR Research Center for Marine Geosciences, Wischhofstraße 1-3, 24148 Kiel, Germany

53

Temperature profiles during a gas hydrate production test

Currently the extraction of gaseous methanefrom natural gas hydrates is discussed as apotential future source of energy. The stabilityof gas hydrates mainly depends on the physical variables of state pressure and tempe-rature. Both the size and the distribution ofnatural gas hydrate deposits, as well as therelease of gaseous methane through the dissociation of gas hydrates, is influenced bythe underground pressure and temperatureconditions.

During the field experiment (Fig. 1), which wascarried out in the framework of the Mallik 2002Research Well Program from December 2001 toMarch 2002 in the Mackenzie Delta in north-western Canada, the spatial and temporal variation of temperature during a gas hydrateproduction test was measured. During the production test the dissociation of gas hydratewas stimulated by circulating hot fluid in a segment of the borehole within the targethorizon. The temperature throughout thedepth of the central production well and twolateral observation wells was recorded withdistributed temperature sensors (DTS).

Through the deployment of the DTS technologycontinuous temperature profiles (distance ofdata points < 1 m) along the boreholes can bedetermined with high temporal resolution(measurement interval > 7 sec). Temperature iscalculated from the reflected signal of a laserpulse transmitted through a optical fibre cable.The temperature data can be registered onlinethrough a opto-electronic surface readout unit.Prior to the field experiment the DTS systemwas calibrated in a temperature controlledchamber at the GFZ Potsdam. With the

calibrated DTS apparatus an accuracy of themeasured temperature data of 0,2 °C can beachieved.

The temperature profiles at the Mallik siteshow characteristic features in the relativelythick permafrost layer (approx. 0m – 600m)and the gas hydrate zone (approx. 900m –1100m). Figure 2 shows a temperature profilefor the Mallik 3L-38 observation well 63 daysafter completion. The base of the ice-bondedpermafrost is marked by a distinct change of thetemperature gradient. Especially in the perma-frost section the temperatures may locally still beunder influences resulting from the drilling andcompletion of the well. As a result of the lowerbulk thermal conductivity, the gas hydratezone shows higher temperature gradients ascompared to the hydrate-free sediments aboveand below.

Figure 3 shows a schematic diagram of thedownhole test configuration and temperatureprofiles in the thermal stimulation zone of theproduction well. The temperature profiles showthe increase in temperature for successive pointsin times from before the test to the maximumtemperature conditions. The distribution of temperature along the wellbore exhibits a cha-racteristic pattern which results from the heatexchange between the well and the surroun-ding formation and the inflow of gas and fluidthrough the perforated section of the boreholecasing.

The first review of the collected field data already shows, that DTS temperature monito-ring is a powerful tool for the observation oftemperature related processes in boreholes.

Henninges, J., Schrötter J., Erbas K., Huenges E., and the Mallik working group

GeoForschungsZentrum Potsdam, AB 5, Telegrafenberg, 14473 Potsdam, Germany

54

With the presented online temperature monitoring system a previously unachievedresolution in space and time could be achieved. The high quality of the collectedtemperature data proves the applicability ofthe system, even under extreme arctic condi-tions. Through the installation of the sensorcables in the cement annulus outside the casingof the borehole, a permanent deploymentwithout interference with other installations inthe borehole was made possible. In combina-tion with other geophysical and geological data,the method is well suited for many differentreservoir engineering applications.

Figure 1: Schematic cross section of the setup for the field experiment. The optical fibre cablesare attached to the outside of the borehole casing and embedded in the cement annulus after completion of the well.

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Figure 2: Temperature Profile for the Mallik 3L-38 observation well 63 days after completion of the well. The profile is characterized by the ice-bonded permafrost layer (approx. 0m to 600m) and the gas hydrate zone (approx. 900m to 1100m) which display different temperature gradients.

Figure 3:Schematic diagram of downhole test configuration and temperature profiles in the thermal stimulation zone. The temperature profiles are displayed for 3h, 20h and 35hafter the start of circulation.

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Pyrite Crusts from the Black Sea:Mineralogy and Genesis

IntroductionPyrite is found abundantly in the uppermostsediments (Unit I and II) of the Black Sea, incontrast to lesser amounts of pyrite in Unit III.It is uniformly dispersed as fine-grained, main-ly framboidal grains (Unit I and II) or anhedralgrains (Unit III). Pyrite (or principal reactants:mackinawite and intermediate reduced S species) in Unit I and II is believed to form withinthe anoxic water column and within the sediment (Muramoto et al., 1991). Sedimentarypyrite formation is limited mainly by iron availability in the most recent (Unit I) non-turbiditic sediments. Berner (1974) recognizedolder sediments (in Unit III) that are black andrich in iron monosulfides (metastable pre-cursors of pyrite), whereas the younger sediments were grey and rich in pyrite ratherthan in iron monosulfides. An upward increasein salinity and consequent availability of sulfatewas suggested to cause the observed succession. In contrast to the above described abundanceof dispersed pyrite in sediments, massive pyritecrusts are a very rare occurrence in the BlackSea, in fact they have been sampled only once,and limited studies were undertaken to elucidate their origin (Lein et al., 1995;Peckmann et al., 2001). Here, we contributenew data on the texture of pyrite, presentingcollomorph textures being a formerly over-looked, but principal feature of the pyrite within the crusts. Stable isotope distributionsof S in the pyrite comprise a narrow range ofsurprisingly positive values close to seawatersulfate-S isotope distributions. A geneticmodel is presented to account for the aboveand previously published results on theseunusual sulfide precipitates.

Material and MethodsThe samples were obtained from the Ukrainianslope in the north-western Black Sea using abeam trawl, which was deployed in waterdepths between 178 – 198 m. The pyrite crustsoccur as individual pieces containing onlynegligible amounts of carbonate, and the carbonate crusts in turn are devoid of pyrite.They have a diameter of up to 15 cm, are firm,dark grey and covered partly with a thin(<1mm), light carbonate. Some pieces showsecondary native S efflorescence. The form ofthe crusts is irregular, some are massive andothers show hollows and irregular tubes, resem-bling fluid pathways as found in high-tempera-ture sulfide chimneys from ocean ridges.

ResultsMineralogy: XRD-analysis of the pyrite crusts revealed thattheir constituents are almost exclusively pyriteand quartz. Measured S-contents of differentpieces of crust were between 21.4-37.7 wt.%,resulting in pyrite contents of 40-70 wt.%,assuming all S is present in pyrite.

Polished sections: From 6 individual crust samples polished sections were prepared and investigated underlight und scanning electron microscope. The fol-lowing textures of pyrite were distinguished:(a) individual angular grains of about 1µm in dia-

meter which are not connected to each other.

Hübner A., Halbach P.

Freie Universität Berlin, FR Geochemie, Hydrogeologie & Mineralogie, Malteserstr. 74-100, Haus B, 12249 Berlin, Germany

sample δ34S (‰) sample δ34S (‰)SMP-A01 9,46 SMP-E01 18,40SMP-B01 17,78 SMP-F01 17,83SMP-C01 18,73 SMP-G01 14,25SMP-D01 15,06

Table 1: S-Isotope distribution of different crust samples

(b) spherical aggregates (framboids: diameter: 5-40 µm) made up of individual pyrite cry-stals (microcrysts) of 1-3µm. Frequently, thelatter show different degrees of amalgama-tion which fill the remaining spaces in bet-ween and induce the formation of massivepyrite spherules.

(c) framboids that are surrounded by a rim ofmassive pyrite. The thickness of the rimvaries from thin, being considerably lessthan the radius of the framboid, to verythick. The rim often shows radial textures.This enclosing rim may be developed furt-her to the next type of pyrite observed inthe crusts:

(d) massive, colloform pyrite (melnikovite) withremnants of framboids. This massive pyriteoften features cauliflower-like banding tex-tures around single or groups of framboidalpyrite crystals.

DiscussionSeep carbonates precipitate on the sea floor ofthe Black Sea around methane gas seeps as aresult of increased alkalinity due to bacteriallymediated anoxic methane oxidation. Anotherproduct of this reaction is dissolved reduced S,which may react with Fe2+ to form pyrite. Onesurprising result of the GHOSTDABS-cruisewith R/V “Professor Logachev” in July 2001 inthe Black Sea was the complete absence ofpyrite from seep carbonates, which wereextensively sampled from the sea floor.Additionally, the pyrite crusts which were sam-pled in an area where seep carbonates dooccur, are free of carbonates, apart from a thincarbonate cover on some parts of the crusts.This leads us to the hypothesis that differentsites of mineral precipitation for these phasesmust exist.

Figure 1: Examples for pyrite morphologies in pyritecrust samples from the Black Sea: from left toright, according to text above (a) individualmicrocrystals, (b) framboids, (c) framboids withrim and (d) colloform pyrite with framboidrelics. Scale bars are 5µm for type (a) and 20µm for types (b) to (d). Types (a) to (c) photosby SEM, (d) photo by light microscope .

Figure 2:Genetic model of pyrite crust precipitation. For explanation see text .

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The exact formation pathway of sedimentarypyrite is still debated, but consensus exists thatpyrite does form mainly via precursor mineralsin the following succession:

Fe2+ + S2- ¢ disordered mackinawite (FeS) ¢ordered mackinawite ¢ greigite (Fe3S4) ¢pyrite (FeS2)

The synthesis of Fe-monosulfides may be writ-ten according to Rickard et al. (1995):

Fe2+ + S2- ¢ FeS + 2H+

In this reaction, protons are produced, whichare considered to play a key role in lowering thepH of the system and therefore inhibit carbonate precipitation at the site of Fe-sulfidemineralisation. In our model, the above reaction takes place within the sedimentarycolumn along the pathways of upwards-migra-ting methane, where S 2 – is produced continu-ously by anaerobic methane oxidation/sulfatereduction. The HCO3

–, which is also a product ofanaerobic methane oxidation, is carried furtherupwards. With contact of the Black Sea bottomwaters, carbonates precipitate and may eventu-ally form chimney-like structures (Fig. 2).

Microorganism activity is assumed to be verystrong along the pathways of migrating methane. Additionally, the supply of dissol-ved suphate to the reaction site is restrictedby the diffusion from the seafloor surface.For these reasons, sulfate-limited conditionsmay develop along and in the vicinity of theseep pathways, leading to nearly-closed-system conditions in the S-system. This sce-nario would cause a _34S signature in pyritesimilar to that of marine sulfate.

The formation of the conspicuous framboidaltexture of pyrite is thought to occur after theconversion of mackinawite microcrystals togreigite, and is attributed to the strong ferromagnetic property of greigite whichattracts single microcrystals to spheric aggre-gates. Contrasting this, colloform pyrite is pro-duced when the rate of crystal nucleation is

greater than the growth rate, implying veryfast reaction of dissolved iron and dissolvedreduced S-species. Further work will be doneto elucidate the formation histories of thesetwo distinctively different textural occurrencesof pyrite in the crusts from the Black Sea.

ReferencesBerner R. A. (1974) Iron sulfides in Pleistocenedeep Black Sea sediments and their paleo-oce-anographic significance. In The Black Sea -Geology, Chemistry and Biology, (ed. E. T.Degens and D. A. Ross), pp. 524-531.American Association of Petroleum GeologistsMemoir, 20.

Lein A. Y., Egorov V. N., Pimenov N. V., GulinM. B., Luth C., Artyomov Y. G., Polikarpov G.G., Thiel H., and Ivanov M. V. (1995) Sulfidechimneys in the Black Sea (in Russian). DokladyRossiiskoi Akademii Nauk. 310, 676-680.

Muramoto J. A., Honjo S., Fry B., Hay B. J.,Howarth R. W., and Cisne J. L. (1991) Sulfur,iron and organic carbon fluxes in the BlackSea: sulfur isotopic evidence for origin of sulfurfluxes. Deep-Sea Research 38 (Suppl.), S1151-S1187.

Peckmann J., Reimer A., Luth U., Luth C.,Hansen B. T., Heinicke C., Hoefs J., and ReitnerJ. (2001) Methane-derived carbonates andauthigenic pyrite from the northwestern BlackSea. Marine Geology 177, 129-150.

Rickard D. T., Schoonen M. A. A., and LutherG. W. (1995) Chemistry of iron sulfides in sedi-mentary environments. In GeochemicalTransformations of Sedimentary Sulfur (ed. M.A. Vairavamurthy and M. A. A. Schoonen), pp.168-193. American Chemical Society.

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Structure and dynamics of gas hydrates:Recent results

Gas hydrates have an ice like structure yet havemany distinct physical properties from ice suchas glass-like thermal conductivity (Anderssonand Ross, 1983; Tse and White, 1988). In spiteof recent investigations, however, there are stillmany remaining unresolved problems relatingto the microstructure and dynamic propertiesof gas hydrates. Molecular dynamics (MD)simulations are powerful tools to investigatethe microstructure and dynamic properties ofgas hydrates. A suitable water potential modelused in MD simulations is a key to correctlypredict their properties precisely. In order toestablish a good interaction model for water ina gas hydrate system, it turns out that a crucial test is the ability to reproduce the lowfrequency modes of gas hydrates. Low frequency dynamic properties of gas hydrateshave been studied using Raman (Nakahara etal., 1988), IR (Klug and Whalley, 1973), andneutron spectroscopy (Tse et al., 1993; Tse etal., 2001; Gutt et al., 2002). From inelasticneutron scattering (INS) experiments we areable to obtain the precise low frequency dataand compare with MD simulation results.However, for methane hydrate, it is difficult todistinguish the lattice modes from CH4 modesbecause of high incoherent scattering crosssection of CH4 (321.0 barn) compared withD2O (4.1 barn). In this study we therefore havedone INS experiments of Ar-, Xe-, O2 - and N2-hydrates with deuterated samples using a timefocusing time-of-flight spectrometer. In addi-tion to the INS experiments, we have demon-strated an accuracy of water potential modelused in the present MD simulations by theassignment of low frequency modes in doublyoccupied N2-hydrates.

Inelastic neutron scattering experiments were

performed using the time-of-flight spectrome-ter IN6 at the Institut Laue-Langevin (ILL) withvarious gas hydrate samples which were inde-pendently prepared from powdered ice Ih. Todistinguish vibrations of guest molecules fromthose of water molecules it is necessary toemploy the sample of deuterated gas hydrates.The material synthesis was performed by expo-sing powdered ice to well-defined gas pressures at well-defined temperatures for twoweeks: D2O (Ar, O2 and N2: 180 bar, Xe: 10 bar,N2: 2 kbar) at 273 K and H2O (N2: 180 bar) at271 K. Details of the sample preparation canbe found in the literatures (Kuhs et al., 1997;Staykova et al., 2002).

Molecular dynamics calculations of N2-hydratehave been performed using the Kumagai,Kawamura and Yokokawa (KKY) potentialmodel (Kumagai et al., 1994) which allowsunconstrained atomic motions. The parame-ters for water were optimized so as to revisethe dielectric constant of liquid water. As aresult the lattice vibrational frequencies ofhexagonal ice Ih are in good agreement com-pared with our old model (Itoh et al., 1996).The parameters for nitrogen were fitted toreproduce the potential curvature for N2- N2

with four different configurations. The modelused in the present MD calculations contains1088 H2O for a structure II clathrate hydratewith cubic Fd3m cell dimensions a = b = c =34.40 Å (2 x 2 x 2 unit cells). We put 128 N2

molecules in small cages and 64 N2 molecules(singly occupied) and 80 N2 molecules (doublyoccupied) in large cages. Both constant volu-me (N, V, T) and constant pressure (N, P, T) MDcalculations were performed for 40 ps(100,000 steps) with a time step of 0.4 fs. The power spectrum, which related to the

Itoh H., Goreschnik E., Klapproth A., Kuhs W.F.

GZG Abt. Kristallographie, Universität Göttingen, Goldschmidtstr. 1, 37077 Göttingen, Germany

60

vibrational density of states (VDOS), is simplythe Fourier transform of the atom velocityautocorrelation function. More details of calculations are described in our previouspaper (Itoh et al., 2001).

We have measured Ar-, Xe-, O2 - and N2-hydrates. Here we present one of our important results that Xe- and N2-hydrate havedifferent spectral features. Figure 1 shows thegeneralized susceptibility χ’’(ω) of Xe- and N2-hydrate in the low-frequency region as a func-tion of temperature. In the Xe-hydrate case(Fig. 1(a)) only the first peak at about 2 meVshows a slight anomalous softening, while thepeak at 2.9 and 4.0 meV does not have tem-perature dependency. The Xe-peak at 2.3 meV(above 100 K) softens slightly with decreasingtemperature to 2.1 meV at 60 K. This is inagreement with the predictions from MDsimulations (Inoue et al. 1996) with a peak at2.5 meV at 260 K shifted to 2.1 meV at 100Kas well as with the experimental results on thehydrogenated system by Tse et al. (2001) andGutt et al. (2002). Moreover, the peak fre-quencies of the Xe-modes obtained in ourexperiment are in good agreement with theresults of MD simulations (Tse et al., 1983;Inoue et al., 1996).

In contrast to Xe-hydrate, the first low frequency peak at about 2 meV in N2-hydratehas very strong temperature dependence. Ascan be seen from Fig. 1(b), the maximum position of the peak in the generalized suscep-tibility χ’’(ω, Q) softens from about 2.2 meV to0.8 meV with the temperature decreasingfrom 160 K to 20 K. The softening is accom-panied by a strong increase in intensity. Thecalculated spectrum of N2 molecules in largecages at 18.6 cm-1 (2.30 meV) is in goodagreement with this peak observed experimen-tally. The N2-mode in large cages has moreanharmonic vibration than the Xe-mode inlarge cages (see Fig. 1(a)). In the frequencyrange over 5 meV we have observed a twopeak structure centered at 7 and 10 meV. Thisspectral feature is distinct from the spectrumof hexagonal ice (which shows only one well-

defined peak at about 6.2 meV) and providesa fingerprint of the open cage structure of thehost lattice. While the peaks are centeredapproximately at the same frequencies asthose in Ar- and Xe-hydrates, the first peak hasa strongly enhanced intensity. The enhance-ment at 7 meV can be assigned to N2 externalvibrations in small cages corresponding to thepeak centered at about 60 cm-1 (7.4 meV) calculated by MD simulations at 180 bar (seeFig. 2). It is dominated by a strong band cente-red at about 7 meV, i.e. exactly at the positionof the first peak of the host lattice. This assign-ment is also supported by the N2-contributionsto the spectrum of N2-hydrate which are calculated from the difference between N2-hydrate and Ar-hydrate.

Inelastic neutron scattering experiments on different types of gas hydrates have been per-formed. In addition we have demonstrated anaccuracy of interaction model for water andnitrogen molecules by the assignment of lowfrequency modes in N2-hydrate. We found thatthe spectral features of two intense peaks atabout 7 and 10 meV are distinct from thespectrum of hexagonal ice and provide a fingerprint of the open cage structure of thehost lattice. From a comparison of the experimental N2-contributions to the spectrumand the results of MD simulations we can clearly assigned N2 internal modes in small andlarge cages. From our INS experiments and MDsimulations, we conclude that not only eachgas hydrate has a different spectral feature forits guest modes but also exhibits a variablecoupling of the guest modes with the host lattice. For instance, comparing the low frequency modes in large cages, Xe-modes areless anharmonic than N2-modes. In additionMD simulations using the KKY potential modelused in this study well reproduced the dynamicproperties of gas hydrates. It is important tonote here that this variation in anharmonicitymay well affect relevant physical properties likethermal conductivities. In this light, generalizedstatements on the respective physical behaviorof gas hydrates seem problematic. Rather itappears that for each hydrate and each gas

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mixture the relationship between structure anddynamics and its physical properties must beestablished on a individual basis before we canattempt a more generalized view.

Figure 1: Generalized susceptibility χ’’(ω) of Xe-hydrate(a) and N2-hydrate (b) in the low-frequencyregion as a function of temperature. Note thedifference in anharmonic shift with tempera-ture especially for the lowest energy mode.

Figure 2: N atom power spectra for small and large cages at80 K and at 180 bar as obtained from a 40 ps MDrun.

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ReferencesAndersson, P., & Ross, R. G. (1983). Journal ofPhysics C: Solid State Physics 16, 1423-1432. Gutt, C., Baumert, J., Press, W., Tse, J. S., &Janssen, S. (2002). Journal of Chemical Physics116, 3795-3799.

Inoue, R., Tanaka, H., & Nakanishi, K. (1996).Journal of Chemical Physics 104, 9569-9577.Itoh, H., Kawamura, K., Hondoh, H., & Mae, S.(1996). Journal of Chemical Physics 106, 2408-2413.

Itoh, H., Tse, J. S., & Kawamura, K. (2001).Journal of Chemical Physics 115, 9414-9420.Klug D. D., & Whalley, E. (1973). CanadianJournal of Chemistry 51, 4062-4071.

Kuhs, W. F., Chazallon, B., Radaelli, P. G., &Pauer, F. (1997). Journal of Inclusion.Phenomena and Molecular recognition inChemistry 29, 65-77.

Kumagai, N., Kawamura, K., & Yokokawa, T.(1994). Molecular Simulation 12, 177-186.

Nakahara, J., Shigesato, Y., Higashi, A.,Hondoh T., & Langway, Jr., C. C. (1988).Philosophical Magazine B 57, 421-430.

Staykova, D. K., Goreshink, E., Salamatin, A.N., & Kuhs, W. F. (2002). Proceedings of the4th International Conference on Gas Hydrates,Yokohama, Japan.

Tse, J. S., Klein, M. L., & McDonald, I. R.(1983). Journal of Chemical Physics 87, 2096-2097.

Tse, J. S., & White, M. A. (1988). Journal ofPhysical Chemistry 92, 5006-5011.

Tse, J.S., Powell, B. M., Sears, V. F., & Handa, Y.P. (1993). Chemical Physics Letters 215, 383-387.

Tse, J.S., Shpakov, V. P., Belosludov, V. R.,Trouw, F., Handa, Y. P., & Press, W. (2001).Europhysics Letters 54, 354-360.

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Geochemical relicts of gas hydrate dissociation in sediments of pockmark sites of the Congo Fan (CONGO)

Detailed sampling of pockmarks has been carried out on the Northern Congo Fan duringMeteor cruise M47/3 in June/July 2000. Fourgravity cores were retrieved that covered orreached almost the depth of complete sulfatedepletion – i.e. the zone of anaerobic oxidationof methane (AOM).

In this contribution we focus on two pockmarksites where the zone of anaerobic oxidation ofmethane was reached at different sedimentdepths (Fig. 1). At the flank of one of the pockmarks (site GeoB 6520) gas hydrates werefound below 5 m sediment depth. Pore waterdata revealed a flux of methane from thehydrate-bearing zone into a sulfate/methanetransition located at about 2.2 m sedimentdepth. A second pockmark site (GeoB 6521)revealed numerous authigenic carbonatesdistributed over the whole sediment depth of11.5 m. The zone of anaerobic oxidation ofmethane at this site is located at a depth of 11m below the sediment surface characterizedby a very narrow zone (app. 1 m) where thegradient of sulfate shows a conspicuous steepening.

Although the gas hydrates found at site GeoB6520 are stable with respect to temperature(3°C) and pressure (3100 m water depth) wesuggest that they will undergo successive dissolution due to the methane concentrationgradient established between the hydrate-bearing zone below and the zone of AOM.Within the hydrate-bearing sediment intervalinterstitial methane is in thermodynamic equilibrium with gas hydrates (e.g., Zatsepina

& Buffett, 1997). The consumption of metha-ne by anaerobic oxidation produces a flux ofmethane from the hydrate zone into the sulfate/methane transition. As a consequencemethane is continuously released from the gashydrates resulting in their successive dissociationirrespective of favorable pressure and tempera-ture conditions.

We assume that at site GeoB 6521 - where nohydrates were found in the upper 11.5 m - gashydrates must have been present there as welland that they are likely to have dissolved according to the process described above. Thelarge amounts of alkalinity produced by theprocess of anaerobic methane oxidation led tothe formation of authigenic carbonates whichare almost homogenously distributed over thewhole sediment depth covered by this core.The dominant phase is Mg-calcite (~13% Mg)followed by aragonite with δ13C values ranging between –44 and –60‰ thus suggesting at least partly a biogenic source ofmethane (Fig. 2). Most of the aragonitic carbonates (associated with increased Sr concentrations) are found in the upper part ofGeoB 6521 indicating that they were formedwhen carbonates precipitation took placeunder oxic conditions close to the sediment/water interface (e.g., Walter, 1986).

Further support for a successive downwardprogression of the zone of anaerobic methaneoxidation induced by dissociation of gas hydra-tes comes from the solid phase distribution ofbarium. Authigenic barites typically precipitateslightly above the zone of sulfate depletion

Kasten, S. (1), Hensen, C. (2), Schneider, R. (1), Spieß V. (1)

(1) Universität Bremen, Fachbereich Geowissenschaften, Postfach 33 04 40, 28334 Bremen, Germany

(2) GEOMAR Forschungszentrum für Marine Geowissenschaften, Wischhofstraße 1-3, 24148 Kiel, Germany

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(e.g., Torres et al., 1996). Numerous distinct Baenrichments found above the present depth ofthe sulfate/methane transition at 11 m indicatethat this geochemical front was located closerto the sediment surface in the past and hassuccessively moved downward (e.g., Dickens,2001). Increased Ba contents mark depthswhere the zone of anaerobic methane oxida-tion was fixed for a significant length of time.Calculations of the time to produce the totalamount of authigenic Ba in the sediment inter-val above the present depth of the zone ofAOM by upward diffusion of Ba2+ give a mini-mum time period of about 18500 years assu-ming an average porosity of 75%.

Our results demonstrate the potential of authigenic minerals formed in the zone of anaerobic methane oxidation to trace chan-ging fluxes of methane from deeper parts ofthe sediment as well as dynamics of formationand and dissociation of marine gas hydrates.

ReferencesDickens, G.R. (2001) Sulfate profiles andbarium fronts in sediment on the Blake Ridge:Present and past methane fluxes through alarge gas hydrate reservoir. Geochim.Cosmochim. Acta, 65, 529-543.

Torres, M.E., Brumsack, H.J., Bohrmann, G. &Emeis, K.C. (1996) Barite fronts in continentalmargin sediments: A new look at bariummobilization in the zone of sulfate reductionand formation of heavy barites in diageneticfronts. Chem. Geol., 127, 125-139.

Walter, L.M. (1986) Relative efficiency of car-bonate dissolution and precipitation duringdiagenesis: aprogress report on the role ofsolution chemistry. In: Gautier, G.L. (Ed.), Rolesof organic matter in mineral diagenesis.Society of Economic Palaeontologists andMineralogists, Special Publications, 38, 1-12.

Zatsepina, O.Y. & Buffett, B.A. (1997) Phaseequilibrium of gas hydrate: Implications for theformation of hydrate in the deep sea floor.Geophys. Res. Lett., 24, 1567-1570.

Figure 1: Pore water concentration profiles for pockmark sitesGeoB 6520 (”Hydrate site”) and GeoB 6521 (”Carbonate site”) on the Northern Congo Fan.

Figure 2: Plot of δ13C vs. δ18O of bulk authigenic carbonates in cores GeoB 6520 and GeoB 6521.

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Geoacoustic mapping of near-surface gashydrates and associated features in theBlack Sea using deep-towed, high-resolutionsidescan sonar.

A newly acquired full-ocean depth, deep-towedsidescan sonar system (DTS-1, Fig. 1) was usedfor the first time during cruise M52/1 to theBlack Sea. The instrument used here allowsimaging the backscatter intensity of theseafloor at high resolution. This surface informa-tion can further be integrated with very high-resolution subbottom information of theuppermost sedimentary layer, therefore allow-ing volume estimates of sedimentary units atthe seafloor. For cruise M52/1 the instrumentwas intended to map the occurrences of near-surface gas hydrates and associated featuressuch as carbonate crusts, gas seeps and pock-marks. As these gas hydrate occurrences in theBlack Sea are closely related to mudvolcanism,the surface expression of these mudvolcanoesand of mudflows originating from representedanother target for the use of the deep-towedsidescan sonar.

The DTS-1 sidescan sonar is a EdgeTech Full-Spectrum (FS-DW) dual-frequency, chirp side-scan sonar working with 75 and 410 kHz centre frequencies. The 410 kHz sidescan

sonar emits a pulse of 40 kHz bandwidth and2.4 ms duration (giving a range resolution of1.8 cm) and the 75 kHz sidescan sonar provides a choice between two pulses of 7.5and 2 kHz bandwidth and 14 and 50 ms pulselength, respectively. They provide a maximumresolution of 10 cm. In addition to the sidescansonar sensors, the DTS-1 contains a 2-16 kHz ,chirp subbottom penetrator providing a choiceof three different pulses of 20 ms pulse lengtheach: a 2-10 kHz pulse, a 2-12 kHz pulse anda 2-15 kHz pulse giving nominal resolutionbetween 6 and 10 cm. The sidescan sonarsand the subbottom penetrator can be run withdifferent trigger modes: internal, external, coupled and gated triggers. Coupled andgated trigger modes also allow to specify trigger delays. The sonar electronics providefour serial ports (RS232) in order to attach upto four additional sensors. One of these portsis used for a Honeywell attitude sensor provi-ding information on heading, roll and pitch.Finally, there is the possibility of recording datadirectly in the underwater unit through a mass-storage option with a total storage capacity of30 Gbyte. The sonar electronic is housed in atitanium pressure vessel mounted on a towfishof 2.8m x 0.8m x 0.9m in dimension (Fig. 1).The towfish houses a second titanium pressurevessel containing the wet-end of the SENDDSC-Link telemetry system. In addition, anOCEANO releaser with separate receiver headthat is now compatible with Posidonia 6000underwater positioning, and a NOVATECHemergency flash and sender are included inthe towfish.

Klaucke I., Weinrebe W., Bohrmann G.

GEOMAR, Forschungszentrum Kiel, Germany

Figure 1: The DTS-1 sidescan sonar towfish during deployment in the Black Sea.

66

Control operations of the DTS-1 sidescan sonarare carried out using Hydrostar Online, a multi-beam bathymetry software developed by ELACNautik GmbH and recently adapted to theacquisition of EdgeTech sidescan sonar data.This software package allows onscreenrepresentation of the data, of the fish’s attitu-de, and of the ship’s navigation. It also allowssetting some principle parameters of the sonarelectronics, such a the selected pulse, therange, the power output, the gain and theping rate. HydroStar Online also allows to startand stop data storage either in XSE-format onthe HydroStar Online computer or inEdgetech’s own format in the FS-DW for laterupload. Simultaneous storage in both XSE andJSF-formats is also possible.

During cruise M52/1 a total of 530 km2 of low-frequency (75 kHz) sidescan sonar, 0.4 km2 ofhigh-frequency (410 kHz) sidescan sonar and410 line km of subbottom profiler data havebeen collected, despite many initial problemswith this new system and new configuration.Data recovered were of generally good qualityand allowed detailed mapping of a number ofmudvolcanoes and the extent of mudflowsgenerated by them. Without penetration ofthe high-frequency sound signal, mudflows

shown on sidescan sonar records are believedto be very young. In this respect, Dvurechenskimudvolcano has shown signs of intense cur-rent activity (Fig. 2). At this time it is not yetsure whether these features are related todownslope movements such as mudflows orresult from deepsea currents.

Mudflows, however, seem laterally fairlyrestricted and follow depressions on the flanksof volcanoes. Although subbottom profilerdata do not provide information about the ageof the deposits, subbottom profiler data fromthe flanks of mudvolcanoes indicate individualflow channels that are stacked with slight lateral shifts. Mudflow activity is either notcontinuous or not very voluminous, because

individual mudflows are separated by thin layers of well-stratified sediment of probablyhemipelagic origin (Fig.3). At present it is notclear whether near-surface gas-hydrates havebeen mapped during cruise M52/1. Processingand interpretation of the sidescan sonar datafrom cruise M52/1 are still going on and need tobe combined with the findings of other groupsworking on data from this cruise and this area.

Figure 2: Example of unprocessed 410 kHz sidescan sonar data from the flanks of Dvurechenski mudvolcano. Width of the sonar swath is 100m and 5 min of data (towing speed 3 kn) are shown.

Figure 3: Example of unprocessed DTS-1 subbottom profiler data from the Black Sea showing a number of mudflows.Please note that the bathymetric profile is not a true profile because of varying altitude of the towfish.

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Molecular Ecology of Anaerobic Oxidation of Methane (BMBF/Geotechnologien project ”MUMM”)

Methane is present in huge amounts in marinesediments and exists either as crystalline, solidphase methane hydrates, or as free gas. Littleof the methane reaches the oxic water columnbecause it is converted to CO2 by micro-organisms in the anoxic sediments. Thus, anaerobic oxidation of methane (AOM) is aglobally significant process, since it decreasesthe flux of the greenhouse gas methane frommarine sediments to the atmosphere. There isstrong geochemical evidence, based on microbial process measurements and stablecarbon isotope data that AOM is directly coupled to sulfate reduction. Recent studiesdemonstrated that AOM is mediated by astructured consortium of sulfate-reducing bacteria belonging to the Desulfosarcina/Desulfococcus group and archaea belonging tothe ANME-2 group (Boetius et al., 2000;Orphan et al., 2001), which is phylogeneticallyaffiliated with the order Methanosarcinales.The ANME-2 group is so far known only from16S rDNA clone libraries; no representatives ofit have yet been cultured.

At the Hydrate Ridge off Oregon, discretemethane hydrate layers occur at the seafloor,at a water depth of 600-800 m, associatedwith intensive venting. The crest of the sou-thern Hydrate Ridge is populated by thick bac-terial mats of the sulfur-oxidizing filamentousbacteria Beggiatoa, and by large communitiesof clams of the genus Calyptogena. Both areindicative of active methane seeping. Un-disturbed cores from Beggiatoa mats,Calyptogena fields, and reference stations wereobtained during RV SONNE Cruise SO143-2

(August 1999) and SO148-1 (July/ August2000; Bohrmann et al., 2000). Integrated over the upper 15 cm, the sulfatereduction rates in the zone of anaerobic oxida-tion of methane (AOM) are >100 mmol m-2 d-1

and represent some of the highest values evermeasured in cold marine sediments. A combi-nation of biomarker studies involving stableisotope analysis and fluorescence in situhybridization shows that structured consortiaof archaea and sulfate reducing bacteria (SRB)are presumably mediating AOM in these sedi-ments (Fig.1A; Boetius et al., 2000). Botharchaeal and SRB biomarkers were strongly13C-depleted, which is indicative of methane-consuming microbial communities. The consortiawere highly abundant in Hydrate Ridge sediments with a maximum of 1x10 8

aggregates cm-3. The consortia-associated cellsaccounted for ca. 90% of total cell numbers in these sediments. The diameter ofthe aggregates ranged from 1µm (aggregatesconsisting of only 2-4 cells) up to ca. 15 µm,with an average of 3.2 µm (Fig.1B).The microbial diversity of different sedimentlayers from Hydrate Ridge (Beggiatoa mat andCalyptogena field) was investigated by 16SrDNA clone library analysis. The bacterial diversity was always high, comparable to thatof coastal sediments. The most abundant 16SrDNA sequences were sulfate-reducing bacte-ria (δ-proteobacteria), γ-proteobacteria andmembers of the Cytophaga/Flavobacterium cluster. Only very few sequences affiliated withmethylotrophic bacteria were retrieved. Thearchaeal diversity, however, was extremely low.The sequences belong to recently described

Knittel K. (1), Boetius A. (1, 2), Lemke A. (1), Amann R. (1)

(1) Max Planck Institute for Marine Microbiology, Bremen, Germany

(2) Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany

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groups of methanogenic archaea, ANME-1and ANME-2, and to one group of uncultiva-ted species within the Crenarchaeota.However, the micro-diversity within these threephylogenetic groups was relatively high, withsequence similarities of 95-100%. The detec-ted bacterial and archaeal diversity is consi-stent with the results from clone libraries fromother methane-rich sites such as the Gulf ofMexico (Lanoil et al., 2001) or the Eel RiverBasin (Orphan et al., 2001). We are also plan-ning to compare the microbial diversity ofHydrate Ridge sediments with other samplingsites with respect to the methane source. FISH analysis showed a highly active microbialcommunity in sediments below the Beggiatoamat and Calyptogena field consisting of about70% bacteria and 30% archaea (Fig.2). Thepercentage of archaea increases strongly withdepth. However, at the reference station the per-centage of archaea is very low, accounting for amaximum of 10% of total DAPI cell counts.

Additional data on the abundance and verticaldistribution of different groups of sulfate-redu-cing bacteria will be presented.

ReferencesBoetius, A., K. Ravenschlag, C. Schubert, D.Rickert, F. Widdel, A. Gieseke, R. Amann, B. B.Jørgensen, U. Witte, and O. Pfannkuche. 2000.A marine microbial consortium apparently medi-ating anaerobic oxidation of methane. Nature.407:623-626.

Bohrmann, G., P. Linke, P. Suess, and O. Pfann-kuche. 2000. RV SONNE Cruise Report SO 143:TECFLUX-I-1999. GEOMAR Rep. 93.

Lanoil, B. D., R. Sassen, M. T. La Duc, S. T. Sweet,and K. H. Nealson. 2001. Bacteria and Archaeaphysically associated with Gulf of Mexico GasHydrates. Appl. Environ. Microbiol. 67:5143-5153.

Orphan, V. J., K.-U. Hinrichs, W. Ussler III, C. K.Paull, L. T. Taylor, S. P. Sylva, J. M. Hayes, and E.F. DeLong. 2001. Comparative analysis ofmethane-oxidizing archaea and sulfate-redu-cing bacteria in anoxic marine sediments.Appl. Environ. Microbiol. 67:1922-1934.

Orphan, V. J., C. H. House, K.-U. Hinrichs, K. D.McKeegan, and E. F. DeLong. 2001. Methane-consuming archaea revealed by directly cou-pled isotopic and phylogenetic analysis.Science. 293:484-487.

Figure1: A. In situ-hybridization of archaea/Desulfosarcinaaggregate with fluorescently labelled rRNA-targeted oligonucleotide probes. The archaea are shown in redand the sulfate-reducing bacteria of the Desulfosarcina/Desulfococcus group in green (picture taken from Boetiuset al., 2000). B. Size spectrum of DAPI-stained aggregates.

Figure 2: A. FISH of sediments covered by a Calyptogena field(Station 185, 0-1 cm depth) with a general bacterialprobe (EUB338 I-III). B. DAPI staining (same microscopic field).

69

MARGASCH – Marine gas hydrates of theBlack Sea: First results from a high resolution3D multichannel seismic survey

The existence of gas hydrates in marine sediments was first proved in the Black Sea,the largest anoxid basin in the world. Sincethen, near surface gas hydrates were regularlysampled in marine sediments of the Black Sea.The main objective of the interdisciplinary research cruise of the German R/V Meteor inearly 2002 (Project MARGASCH: Marine gashydrates of the Black Sea) was to study thedistribution, structure, and architecture of gashydrate occurrences in the Black Sea as well astheir relationship to fluid migration pathways.The investigations were concentrated in twoareas: the central Black Sea and the SorokinTrough, southeast of the Crimean peninsula.Here we will present seismic data from theSorokin Trough (Fig. 1).

A GI-Gun with 0.4 L chamber volume (100-500 Hz) and a Sodera water gun (200-1600Hz) were used in an alternating mode along allseismic lines. The data were recorded bymeans of a 600-m-long Syntron streamer (48channels) equipped with separately pro-grammable hydrophone subgroups. Hydro-acoustic systems (Parasound, Hydrosweep)were used simultaneously on each seismic lineduring the cruise. The seismic survey was divided into two parts. 44 seismic lines wereshot as overview profiles to image the principalstructures of the survey area. Based on theseresults we chose a 2.5 km x 7.5 km large boxfor a three-dimensional survey with a line spa-cing of 25 m (Fig. 1).

Krastel S., Spieß V., Zühlsdorff L.

Dept. of Geosciences, University of Bremen, P. O. Box 330440, 28334 Bremen, Germany, skrastel@uni-bremen.de

Figure1:Profile plan of the seismic survey in the Sorokin Trough.

70

The Sorokin Trough is characterized by diapiricstructures and compressional tectonics thatfacilitate fluid migration to the seafloor.Abundant mud volcanoes and near surface gashydrate occurrences were identified in thisarea. The seismic overview profiles allows toimage these features. The diapiric ridges are ofparticular interest since they are caused by theprotrusion of plastic, water-saturated Maikopianclays. The ridges strike in a WSW-NEN direction, which is parallel to the general trendin the Sorokin Trough. Mud volcanoes arefound above the diapiric ridges.

A typical example crossing two different typesof mud volcanoes is shown on Line GeoB 02-003 oriented in a SSW-NNE direction (Fig. 2).The larger mud volcano at the southwesternend of the profile is the Kazakov mud volcano.Kazakov mud volcano is cone-shaped with adiameter of ~ 2.5 km and a height of ~ 120 mabove the surrounding seafloor. The areabeneath Kazakov mud volcano is characterizedby a transparent zone with a width similar tothe diameter of the mud volcano probably serving as the main feeder channel. This zonecan be vertically traced to more than 1.5 sTWT, which is the maximum seismic penetra-tion of our system. Whether Kazakov mud volcano is located on a fault zone is not clearly imaged by the seismic data but reflectors,which could be identified in the upper part ofthe section, do not show a major offset.

Another type of mud volcanoes is located bet-ween CMPs 850 and 1100 on Profile GeoB 02-003 (Fig. 2). These volcanoes belong to a beltof mud volcanoes associated with a morpholo-gical step. The diameters of the mud volcanoesimaged on Line GeoB 02-003 are ~ 1 km forthe mud volcano located around CMP 900 and500 m for the mud volcano at CMP 1050; theheights are 45 m and 15 m, respectively. Thefeeder channel in the upper 300 – 400 ms TWTreveals about the same diameter as the mudvolcano itself. Diapirs are clearly imaged beneath. These structures are interpreted asmud diapirs originating from the Maikopianformation, which is characterized by low-

density clays and plastic behavior. In total,three different types of smaller mud volcanoeslocated above or on the edges of near surfacemud diapirs can be distinguished in theSorokin Trough: cone-shaped, flat-topped, andcollapsed.

Despite the known near-surface occurrences ofgas hydrates, bottom simulating reflectorswere not present in our seismic lines. The reason for this might be that gas hydrates didnot occur as massive gas hydrate layers but arefinely dispersed in the sediments. However,pronounced lateral amplitude variations andbright spots may indicate the occurrence ofgas hydrates and free gas but more detailedprocessing and interpretation of the seismicprofiles is necessary to identify and quantifygas hydrates and free gas.

Based on the results of the overview profiles a2.5 km x 7.5 km large box was chosen to collect a three-dimensional seismic data set.This data set will allow to trace structural features, amplitude variations, and pathwaysfor fluid-flow in three dimensions. All shots of the three-dimensional survey were alsorecorded with 14 Ocean Bottom Hydrophones/Seismometers and these data will be used fora seismic tomography. Both data sets will bejointly interpreted.

A lot of questions remain open at this early stage of the project. Key questions are:- What causes the different shapes of the mud

volcanoes?- Are different forms of mud volcanoes bound

to particular features in the subsurface?- What is the relationship between mud volca-

noes, gas hydrate occurrences, and free gas? - How are gas hydrates laterally distributed

and is it possible to quantify the gas hydrates?We hope to answer these questions by a detailed analysis of the seismic and other datacollected during the cruise. The data set consisting of geological, geochemical, andgeophysical data provide a great opportunityto improve our knowledge on the distribution,structure, and architecture of gas hydrate

71

occurrences in the Black Sea, and on their rela-tionship to fluid migration pathways.

Figure 2:CMP-Stack of seismic Line GeoB 02-003 crossingKazakov mud volcano and group of unnamed mud volcanoes. CMP distance is 20 m.

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Microbial methane turnover in different typesof marine sediments – The MUMM-Project –

IntroductionThe abundance of active CH4 seeps, like gashydrates, mud volcanoes, leaks of gaseous CH4

and organic rich sediments, illustrates theimportant role of the oceans in the global CH4

cycle. However, in contrast to terrestrial andfreshwater habitats, much less is known aboutthe processes and microorganisms involved inthe CH4 turnover in marine environments.Within the MUMM-project we therefore investigate the processes involved in CH4

production and consumption at a number ofmarine sites (Figure 1), with a special focus ongas hydrate bearing sediments. Samples collected at CH4 seep areas are compared tocontrol sites with normal background CH4

concentrations. Rates of anaerobic (AOM) andaerobic CH4 oxidation together with CH4

production are determined combining radio-tracer (on-site) and in-vitro measurements.

Results & DiscussionIn the present study we demonstrated for thefirst time net AOM in sediment samples(Hydrate Ridge) under laboratory conditions(Nauhaus et al. 2002). Furthermore, we couldshow that the stoichiometry of AOM is inaccordance with the equation CH4 + SO4

2 – ¢ HCO3

–+ HS

–+ H2O.

The comparison of AOM-rates obtained withthis new method or using radiolabeled CH4

resulted in similar values (Figure 2). The esta-blishment of a method for the in-vitro deter-mination of AOM and the availability of activesediments allows further detailed studies ofthe processes and mechanisms of AOM as wellas of the microorganisms involved.

The rates of AOM in samples from gas hydrateareas and methane seeps are several times higher than in low-methane sediments.Additionally, aerobic methane oxidation wasimportant at many sites where the sedimentwas in contact with oxic bottom water. Here,rates of aerobic methane turnover were similar

Krüger M., Treude T., Nauhaus K., Eppelin A., Boetius A., Widdel F.

Max-Planck-Institute for Marine Microbiology, Celsiusstrasse 1, 28359 Bremen, Germany

Figure 1: Map with the distribution of important sampling sites for the MUMM-project.

Figure 2: Comparison of rates of anaerobic oxidation of CH4 attwo sites, either determined on-site using 14 C-labeledCH4 or in vitro via sulfide production (mean ± SD, n = 3-5).

73

to those of anaerobic methane oxidation. Afirst estimation of aerobic and anaerobic oxidation activity showed that methane consumption in low-methane sediments, whichare most widespread, is on a global scale quantitatively at least equally important, despitethe higher rates (per volume) of methane oxidation in and near seeps. Methane produc-tion in organic-rich subsurface sediments wasgenerally high, especially if sulfate as electrondonor was limiting. These results support therole of methanogenesis as important methanesource in the marine cycle.

OutlookCurrent and future experiments are focused on(I) detailed CH4 turnover measurements atmethane seeps and control sites, (II) the identityof the intermediate(s) shuttled in the consortiumand other aspects of AOM physiology, and (III)the isolation and identification of key microorga-nisms involved in aerobic and anaerobic metha-ne oxidation, and CH4 production.

MethodologyRates of AOM were determined with radiotra-cers (Boetius et al. (2000), Nature 407, 623-626), or using a newly developed in-vitromethod via the monitoring of sulfide produc-tion (Nauhaus et al. (2002), EnvironmentalMicrobiology, in press). For the latter, sulfideproduction from sulfate is compared in thepresence or absence of CH4. Rates of aerobicCH4 oxidation and of CH4 production weredetermined non-radioactively (Krüger et al.(2001), Global Change Biology 7, 49-61).

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Physico-chemistry and properties of gas hydrates: Preliminary answers to some open questions.

We present a number of open questions relatedto the physico-chemical properties of naturalgas hydrates. The questions concern themicrostructure, some theromodynamic aspectsas well as the formation and decompositionkinetics of these compounds. We were tacklingthese questions experimentally employing anumber of techniques (diffraction, Raman- andinelastic neutron scattering, electron microscopyand computer simulations).

Physical propertiesA number of physical properties of natural gashydrates are still poorly known. The more pro-minent gaps are thermal conductivity, thermaldiffusivity and the acoustic wave velocities. Herewe concentrate on the latter. The knowledgeof acoustic velocities is of considerable impor-tance to the interpretation of seismic data.Recent attempts to establish them by adiabaticmethods (transducer measurements) proveddifficult (Helgerud 2001) as sample compac-tion is a non-trivial process. We have now forthe first time successfully measured the iso-thermal compressibilities of pure methanehydrate. The results are shown in Fig.1.

Cage filling and stoichiometryEssentially all predictions of the stoichiometryof gas hydrates are based on the statisticalthermodynamic theory of van der Waals andPlatteeuw (1959). The validity of this theoryhas not been thoroughly checked so far. Mostmethods do not allow to determine the abso-lute filling of both small and large cages. Onlydiffraction can give definite answers. We nowhave obtained first results on the filling forsmall and large cages in the system CH4•xH2O.

While the large cages are almost completely fil-led, the small cages show a significantly lowerfilling than expected from the statistical ther-modynamic theory as shown in Fig.2.

Microstructure and kineticsGas hydrates were found to exhibit sub-micronporosity (Kuhs et al.2000). The porous micro-structure may well influence a number of phy-sical parameters (thermal conductivity, wavespeeds) as well as the mechanical and thermalstability of gas hydrates. At present it is stillunclear to what extend this sub-micron porosi-ty exists in natural settings. Based on our labo-ratory experiments the existence of sub-micronporosity seems to be indicative for fairly fastformation processes (on a time scale of days toa few weeks) with excess of gas. In a separatepaper (poster 28) we present aspects of thereaction kinetics of porous hydrates togetherwith a mathematical model for the growth(Salamatin & Kuhs 2002, Staykova et al. 2002).Sub-micron porosity was found in natural gashydrates in a collaborative effort with GEO-MAR on samples from Hydrate Ridge (Suess etal. 2002). By a comparison of samples fromour laboratory experiments with natural mate-rial from the sea floor we can deduce the con-ditions of growth of the latter.

Molecular modellingComputer simulations are an important tool tointerpret a number of experimental results. Thenature of gas-water and water-water interac-tions on a molecular level is still far from beingunderstood. We have refined existing interac-tion potentials to fit and interpret neutronscattering results on the dynamics of host-

Kuhs W.F., Klapproth A., Itoh H., Goreshnik E.

GZG Abt.Kristallographie, Georg-August Universität Göttingen, 37077 Göttingen, Germany

75

guest interactions (Chazallon et al. 2002, Itohet al. 2002) a summary of which is presentedin a separate paper (poster 27). With such refi-ned interaction potentials we expect to be ableto better predict stability limits as well as thecomposition of pure and mixed gas hydrates.

ReferencesChazallon, B., Itoh, H., Koza, M, Kuhs, W.F. &Schober, H. (2002) Phys.Chem.Chem.Phys. sub-mitted

Helgerud, M.B. (2001) PhD-Thesis, StanfordUniversity.

Itoh, H., Chazallon, B., Schober, H., Kawamura,K. & Kuhs, W.F. (2002) Proceedings of ICGH-2002.

Kuhs, W.F., Techmer, K., Klapproth, A.,Gotthardt, F. & Heinrichs, T. (2000) GRL 27,2929-2932.

Salamatin, A.N. & Kuhs, W.F. (2002). Proceedingsof ICGH-2002.

Staykova, D.K., Hansen,T., Salamatin, A.N., Kuhs,W.F. (2002) Proceedings of ICGH-2002.

Suess, E., Bohrmann,G.,Rickert, D., Kuhs, W.F.,Torres, M.E., Trehu, A. & Linke, P. (2002).Proceedings of ICGH-2002.

Van der Waals, J.H. & Platteeuw, J.C. (1959)Adv.Chem.Phys. 2, 1-57.

Figure 1:

Lattice constants of deuterated and hydrogenated

methane hydrate vs. gas pressure. The slope gives the

bulk modulus which is different for both materials. The

hydrogenated system delivers a value of 9.11 GPa, the

deuterated system a value of 8.21GPa. These isothermal

values can be transformed into adiabatic values using

standard thermodynamic relations to give 9.9 GPa and

8.9 GPa for the hydrogenated and deuterated system

respectively.

Figure 2:

The filling of the small cage in a type I methane hydrate

structure at T=271K as a function of methane fugacity.

The data cannot be fitted satisfactorily with a Langmuir-

isotherm. Langmuir-isotherms taken from literature

predict distinctly higher fillings incompatible with our data.

76

Experimental methods for the laboratory investigation of gas hydrate containing sediments

IntroductionEstimations of the natural methane hydrateresources vary over at least one order, which ispartly due to questionable interpretations ofgeophysical parameters. The petrophysicaldata base on which such interpretations arebased is very weak and the conditions formethane hydrate generations, stability, anddecomposition are not well understood.This is the reason for the initiative at the GFZ toinvestigate physical properties of naturalmethane hydrate and the hydrate formationprocess in the laboratory under well-character-ized conditions. The aim of the laboratory investigations is to develop empirical relationsand theoretical models for the formation ofgas hydrates in sediments and for their physical properties.

Field laboratory for the investigation ofnatural gas hydratesA Field Laboratory Experimental Core AnalysisSystem (FLECAS) for the determination of physical properties of gas hydrate containingsediments was developed and successfullyapplied at the Mallik research well. The advan-tage of such a field system is that there is noneed for transport and storage over a longperiod, so that the sample alteration can beminimized.The experiments yield data sets for the electrical resistivity, ultrasonic p- and s-wavevelocities and absorptions, as well as thehydrate content, porosity, and permeability ofthe samples. Because the experiment starts at

deep frozen condition it also models the con-dition of gas hydrates in the permafrost zone.The setup consists of a pressure vessel with aninternal heat exchanger for cooling the samplebelow the freezing temperature. Methods toprepare the samples at low temperaturewithout thermal stress have been developed.The sample is inserted into the vessel at deepfrozen conditions, when the hydrates are practically stable. The confining pressure (simula-ting the in situ lithostatic pressure, typically 20MPa at 900 m) and a pore pressure with nitro-gen gas (simulating the hydrostatic fluid pressure, 10 MPa at 900 m) are applied. Thenthe sample is heated to the in situ temperature,holding confining and pore pressure constant.During the whole procedure electrical resistivi-ty (with a 6 electrode setup) and ultrasonic p- and s-wave velocities are monitored and theend point yields the geophysical propertiesunder in situ conditions.After reaching the in situ temperature thehydrate decomposition is initiated with a porepressure drop, releasing the N2 gas and thefree pore water. At this moment, both theultrasonic attenuation and velocity decreasestrongly, while the resistivity increases due tothe loss of pore water. The dissociation startsimmediately, which is obvious from the suddentemperature decrease of the sample. Then themethane gas builds up a pore pressure, andthe resistivity decreases again, which is due tothe released hydrate water. At last the gas isreleased through a flow meter for volumedetermination and stored for chemical analy-

Kulenkampff J. (1), Spangenberg E. (1), Naumann R. (2)

(1) Department of Petrophysics and Geothermics, GeoForschungsZentrum, Telegrafenberg, 14473 Potsdam, Germany,

hannes@gfz-potsdam.de, erik@gfz-potsdam.de

(2) Department of Material Properties and Transport Processes, GeoForschungsZentrum, Telegrafenberg,

14473 Potsdam, Germany, rudolf@gfz-potsdam.de

77

sis. Then the hydrate water is pushed out witha N2 - flow through the sample. The hydratecontent can be determined from the hydratewater content and the methane volume.Synthetic gas hydrate containing sedimentsAnother laboratory gas hydrate experimentalapparatus is set up to simulate the conditionsunder which gas hydrate forms in the sea floorsediments and in the permafrost regions (pressure range: 0-20 MPa; theoretical tempe-rature range of the apparatus: (-5 – 40 °C).This apparatus allows measuring seismic velo-city, electrical resistivity, and thermal conducti-vity under in situ conditions. It consists of a 2-chamber insulation box. The first chamber ofthe insulation box is kept on a temperatureabove the stability field of the hydrate andcontains the pressure vessel where the water ischarged with methane. The water with thesolved methane is pumped into the measuringcell in the second chamber of the insulationbox, which is kept on a temperature within thehydrate stability field. Hydrate forms withinthe artificial sediments in the cell from waterand solved methane. The physical properties ofthe sediments can be measured. The processof hydrate formation out of a solution of waterand methane is a very slow process. The firstexperiments have shown, that the determina-tion of the amount of hydrate formed in thesediment from the pressure drop in the systemis difficult because the pressure drop from normal leakage is higher than that from hydrateformation. To overcome this problem we deve-loped an inline high-pressure conductivity cellto calculate the amount of hydrate from theincrease in conductivity. The conductivity ofthe pore water increases during hydrate for-mation because salt is not build into the hydra-te structures and the salinity of the remainingpore water increases with increasing amountof formed hydrate.

Structural investigationThe mineralogical structure of the synthesizedsamples is investigated with Laser Raman spectroscopy and powder X-ray diffraction. ADilor XY Laser Raman Triple 800 mm spectro-meter equipped with an Olympus optical

microscope and a long distance 80x objectivewas used. Spectra were collected with aPeltier-cooled CCD detector. The 488 nm lineof an Ar ion laser and a power of 400 mW wasused for sample excitation. Spectra were obtained from different grains. The spectrumfromeach spot was averaged over 5 accumula-tions. The signal was integrated 20 s for eachaccumulation. All investigated methane hydra-te samples are sI-hydrates.

X-ray diffraction applied with a freezing stageis used for the identification of hydrate phasesand determination of the ice-hydrate propor-tions and lattice constants.

Figure 1:Measurement result with FLECAS:1) relative resistivity change, compressional wave

velocity (uncalibrated) and relative amplitude2) injected oil volume and sample length3) pore pressure and confining pressure (20MPa)4) temperature (v1,v2: vessel; s1,s2: sample).

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Status of development of long-term observatories for gas hydrate research within the collaborative project LOTUS

The overall objective of LOTUS is to monitor insitu the complex trigger mechanisms of forma-tion and destabilisation of gas hydrates on different time and space scales and thus contribute to improved mass balances and diagenetic and prognostic modelling. This willbe realised by deploying novel video-guided,long-term observatories for the sedimentwater interface (SP 1) and the water column(SP 2), by dating and interpretation of thenatural geo-archives (SP 3) as well as by pro-cess-oriented modelling of the benthic processes (SP 4).

Within subproject 1 of LOTUS, the temporalvariability of physico-chemical and biogeoche-mical mechanisms during decomposition andformation of gas hydrates will be studied usingtwo novel benthic observatories. Measurementswill be performed on time scales which are longenough to record the range of naturally occurring control factors. This is in contrast toformer short-term measurements which wereconducted only in the range of hours (biologi-cally mediated processes) to weeks (fluid fluxmeasurements).

The Fluid-Flux-Observatory is applied to thecomplex physico-chemical controlling mecha-nisms of decomposition and formation of gashydrates, inducing different forms of fluid flu-xes (efflux, stagnation, influx), at time scales ofweeks to several months. Changes of tempe-rature, pressure, micro-seismicity, near bottomcurrents (induced e.g. by tides), the release andbuoyancy of gas bubbles and related complex

processes in a two-phase flow system aremonitored.

The Biogeochemical Observatory collects dataon the temporal variability of the biologicallymediated methane turnover at the sedimentwater interface within lander-integrated mesocosms over time scales of days to 1 week.Inside the mesocosms the abiotic ambient environment (e.g. oxygen content, flow regime)is actively maintained and continuously adjustedto changes of these parameters (intelligentsystem). Using an experimental approach thecoupling between the benthic methane turnoverand changes of environmental conditions (e.g.oxygen content, flow regime, and flux of organiccarbon) is simulated inside these mesocosms.

Within subproject 2, the fate of methane in thewater column is elucidated with a variety ofnovel observatories. As free gas is regarded asan important methane source, a sonar-likeswath system “Gas-Quant” was developed incooperation with L3-communications ELAC-Nautik. Integrated into a lander system, it isused for long-term quantification of gas plu-mes emanating from the seafloor. ImprovedMETS methane-sensors (CAPSUM) are deploy-ed in distinct water layers within a mooring todetermine the dissolved methane content overextended time periods. Finally, the impact onthese plumes by the complex hydrodynamicregime within and beyond the gas hydrate sta-bility field is monitored with a long-rangingADCP mounted to another lander.

Linke P. (1), Pfannkuche O. (1), Gust G. (2), Sommer S. (1), Gubsch S. (2), Poser M. (3), Greinert J. (1)

(1) GEOMAR Forschungszentrum für Marine Geowissenschaften, Kiel, Germany

(2) Meerestechnik 1, Technische Universität Hamburg-Harburg, Germany

(3) Oktopus GmbH, Hohenwestedt/Kiel, Germany

79

Distribution of Methanotrophic MicrobialCommunities at the Haakon Mosby MudVolcano (MUMM project)

Microorganisms living in anoxic marine sedimentsare consuming more than 80% of the methaneproduced in the world’s oceans. Thus, anaerobicoxidation of methane (AOM) is a globally signifi-cant process, since it decreases the flux of thegreenhouse gas methane from marine sedimentsto the atmosphere. AOM is thought to be mediated by a structured consortium consisting ofmethanogens and sulfate-reducing bacteria.The most important focussed sources ofmethane in marine environments are gashydrates, methane seeps and mud volcanoes.Mud volcanoes are located at all continentalmargins where large gas deposits are locatedbeneath the seafloor. While first results are avai-lable on AOM at gas hydrates and methaneseeps, little is known about the microorganismsmediating AOM at mud volcanoes. We investigated the Haakon Mosby MudVolcano (HMMV, Barents Sea) as one geologicalmodel system representative. The HMMV islocated on the continental slope north-west ofNorway at a water depth of 1250 m. Its dia-meter is about 2 km, with an outer rim popu-lated by methane-depending, chemosyntheticcommunities and an inner center of about 500m in diameter where fresh mud is expelled. Themicrobial community structure and diversity insediments from three different sampling siteswere investigated by fluorescence in situ hybri-dization (FISH). Additionally, 16S rDNA clonelibraries for bacteria and archaea were con-structed. More than 400 clones were screenedby amplified ribosomal DNA restriction analysis(ARDRA) and phylogenetically analyzed.

The composition of the microbial communityvaried significantly across different HMMV sitesand depended on the methane concentrationsin the sediment. In contrast to other methane-rich environments the bacterial diversity wasrelatively low. The most abundant clonegroups belonged to methylotrophic bacteria(Methylomonas sp., Methylophaga sp.),Cytophaga sp. and some groups of sulfate-reducing bacteria. Archaeal sequences werefound and could be affiliated to the archaealgroups ANME-1 and ANME-2.FISH experiments showed that the microbialcommunity in sediments from below a mat ofgiant sulfide-oxidizing bacteria in the southernpart of the HMMV is dominated by archaea. Incontrast to gas hydrate sites (e.g. HydrateRidge), mostly non-structured aggregates werefound in high numbers (up to 2x107 /cm3 ). Onlyfew aggregates occurred in direct physicalassociation with bacteria. More frequentlymonospecies aggregates of archaea werefound, which could be affiliated to the ANME-2 group (Fig. 1). This archaeal group belongs tothe order Methanosarcinales and is known tobe capable of AOM (Boetius et al., 2000;Orphan et al., 2001).

Lösekann T. (1), Nadalig T. (2), Knittel K. (1), Boetius A. (1, 2), Sauter E. (2), Schlüter M. (2),

Klages M. (2), Amann R. (1)

(1) Max Planck Institute for Marine Mikrobiology, Bremen, Germany

(2) Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany

80

Only few structured aggregates were foundand these looked very similar to the consortiadetected in Hydrate Ridge and Eel River BasinSediments (Boetius et al., 2000; Orphan et al.,2001). In contrast to these already describedaggregates, the bacterial partner in HMMVaggregates could not be affiliated to a knowngroup of sulfate-reducers and still needs to beanalyzed phylogenetically.In the central barren area of the HMMVmethane seeps directly from the sediments tothe hydrosphere. At this site consortia abundance is several orders of magnitudelower than at the Beggiatoa site. The lowabundance of consortia correlated with themethane seeps indicates that methane-oxidizing microorganisms could represent anefficient biofilter reducing the methane emis-sion to the watercolumn. Additional data on consortia abundance, verti-cal and spatial distribution will be shown.

ReferencesOrphan et al. (2001): Methane-ConsumingArchaea Revealed by Directly Coupled Isotopicand Phylogenetic Analysis. Science 293

Boetius et al. (2000): A marine microbial con-sortium apparently mediating anaerobic oxida-tion of methane. Nature 407

Figure 1: Fluorescence in situ hybridization of non-structured ANME-2 archaeal aggregates a) = left, Epifluorescence micrograph of HMMV

aggregates stained with DAPIb) = right, Epifluorescence micrograph of HMMV

aggregates hybridized with probe EelMS932.

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Mallik 2002: The Mallik Data and Information System

During the drilling period of the main well hole(Mallik5L-38) we were able to elaborate aninformation system very close in time andspace to the activities and operations at theMallik drill site and in the laboratories of theInuvik Research Center.The first approach of the data managementfor the Mallik drilling project was the set up ofa database structure using the DrillingInformation System (DIS). The DIS is an electronical toolbox developed for scientificICDP drilling projects. It includes a well-testeddata model which covers the major entities ofthe drilling phase, such as drilling engineering,the documentation and archiving of core runsand samples, initial lithological descriptions,borehole measurements, and monitoring data.This system encompasses various componentshelping in administration and operation of thesystem as well as in presentation of the data.All data are stored in the backend databasemanagement system Microsoft SQL Server2000 which is covered by a Microsoft Access2000 user interface. The database management system was implemented on a server at the Inuvik ResearchCenter. The data entered into the system weredirectly saved on this central server. The underlying data model had to be adaptedseveral times according to particular require-ments and problems of the hydrate researchwell. Instead of a highly differentiated internalnetwork infrastructure, we chose a simplermodel, including the DIS server itself, one clientand the core scanner server (see figure 1).The second main pillar of our work in Inuvikwas the core scanner, which was also connected to the system, and which provided

high resolution images which also were storedin the database. Each of the 210 liners of frozen and unfrozen cores, which came toInuvik could be photographed in a slabbedmode. The expected problems concerning theextreme conditions of temperature caused nobig difficulties.Finally, an important aspect of the project wasto inform the participating scientists about theprogress of the drilling during the active operational phase. Each day during the project'speriod, we used to send updated informationcontaining drilling reports and data from thecoring phase to the Mallik Web site within theICDP Information Network. All digital core pic-tures and archiving information of the coreruns were put to our confidential Web sites,under extremely high security.After the fieldwork of the Mallik project, whichwas our first involvement in the highly sensitiveGas Hydrate Research, we have gathered a lot ofexperience and we can underline the success ofthe data management up to the present.

ReferencesConze, R., Wächter, J. (1998): The ICDPInformation Network (http://www.icdp-onli-ne.de). - (poster and on-line presentation),AGU Fall Meeting, December 6-10, 1998, SanFrancisco, California, USA.

Conze, R., Krysiak, F. (1999): ICDP On-SiteDrilling Information System. - Demo CD inclu-ding an exemplary data set of HSDP2 drilling,GFZ Potsdam, Germany.

Löwner R. (1), Conze R. (1), Wächter J. (1), Krysiak F. (2), Laframboise R. (3), and the Mallik working group

(1) GeoForschungsZentrum Potsdam, Telegrafenberg, D-14473 Potsdam, Germany

(2) smartcube GmbH, Wermuthweg 7, D-12353 Berlin, Germany

(3) Geological Survey of Canada, Terrain Sciences Division, Ottawa, Ontario K1A 0E8, Canada

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Figure 1: Internal Network Structure used at the Inuvik Research Center.

83

Acoustical studies in the water column in vicinity of Cold Vents and Mudvolcanoes

Gas hydrates today are known to occur all overthe world and to constitute large reservoirs inpermafrost soils and marine sediments. Researchactivities in this topic therefore gained a lot ofattraction in the last years.

In the Black Sea, which is the largest anoxicbasin in the world, methane hydrates werealready discovered in 1974. Since then, regularly sampling of the marine sedimentsthere showed frequent occurrence of near surface gas hydrates. Furthermore, the ventingof gas bubbles in the water column could bedetected with appropriate echosoundingsystems as well as directly observed with videosystems. The existence of such gas plumes canusually be related to near surface gas hydrates inthe sediments.

During cruise Meteor M52/1 in January 2002, amultitude of acoustic systems was used to studythe occurrence, structure and distribution of gashydrates in the Black Sea. One of the goals inthis project was, to try to detect the venting ofgas hydrate bubbles in the water column withthe shipboard narrow-beam echosoundingsystem Parasound ‘on the fly’ during normal profile operation. However, to detect gas bubblesin the water as a scatter source for acousticalwaves, the wave length of the sound signal andthe size of the bubbles should be of similar dimension. As the main Parasound signal frequency is only 4 kHz, efforts have been unter-taken in Subproject 2 of the LOTUS project toadapt the digital recording system ParaDigMA)to record also the 18 kHz-signal of theParasound system. In a first attempt, this wasachieved by installing a secondary recording

system specifically redesigned for the 18 kHz signal. This is still a comparably low frequency todetect bubbles of mm to cm size, but dampingof the signal energy in the water column makesbubble detection in greater water depth difficultfor ultra high frequency echosounders.

First model results showed, that the 18 kHz frequency is nevertheless suitable to detect gasbubbles down to 2 – 3 mm in size, if the signalto noise ratios are sufficient. Studies in an arealocated in water depths of 100 to 800 m in aregion, where the venting of gas bubbles is wellknown, then confirmed with no doubt, thatbubbles can be recognized with the 18 kHz-signal of Parasound. This allows to analyze thelinkage between the venting of gas and thestructure of the underlying sediments directly,because both signals, the one penetrating theseafloor and the one detecting the bubbles areemitted and recorded in parallel (Fig. 1).Henceforth the newly designed Parasoundrecording systems will prove as a valuable tool inlocating and studying the escape processes ofgas hydrates at the seafloor and in the watercolumn.

Lom-Keil H. von (1), Spieß V. (1), Krastel S. (1), Greinert J. (2), Artemov Y. (3)

(1) University of Bremen, Germany, hvlom@uni-bremen.de

(2) GEOMAR Research Center for marine Geosciences, Germany

(3) CIME Center for International Marine Explorations, Ukraine

84

Figure 1: Parasound section recorded at a water depth of 500 m. Top: 4 kHz parametric signal showing true topography and internal sediment structure down to a penetration depth of30 mbsf. Bottom: parallel recorded 18 kHz signal. The echogram delay is shifted verticallyto eliminate seafloor topography. Bubble vent sites can be clearly identified as scatter sources in the water column.

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A first estimate of the volume of methane gasassociated with gas hydrate occurrence in theDnieper Canyon area, northwestern Black Sea

Within the framework of subproject 2 of theGHOSTDABS project “Gas Hydrates: Occurrence,Stability, Transformation, Dynamics, andBiology in the Black Sea”, a reflection seismicstudy was carried out in the northwesternBlack Sea west of the Crimean Peninsula. 1100km of high-resolution seismic lines were obtained with an 8-channel mini-streamerhaving an active length of 100 m. A mini-GIgun triggered in the harmonic mode with atotal chamber volume of 0.98 l and a frequencyspectrum extending from ca. 20 to 300 Hz served as the seismic source. The seismic tracks cross the continental margin from theouter shelf (water depth ca. 80 m) to the deepbasin near the location of the MSU MudVolcano (ca. 2100 m).The goals of this subproject are: (1) to map thegas hydrate-cemented horizons on the north-western continental margin of the Black Seausing reflection seismic techniques; (2) to estimate the distribution and possible volumeof gas hydrates within the sediments in combi-nation with seismic refraction results obtain bythe research group of Prof. Dr. Flüh (GEOMAR,subproject 5); (3) to find appropriate locationsto study gas and fluid venting, mud volcanoesas well as gas hydrate outcrops at the seafloor;(4) to evaluate the local tectonic regime inorder to improve the prediction of the stabilityof the gas hydrate deposits; and (5) to characterise the depo-environment by a seismo-stratigraphic interpretation of thereflection seismic data collected as well as bytheir correlation with the sedimentary faciesdeduced from selected cores obtained by theresearch group of Prof. Dr. Reitner (Universityof Göttingen, subproject 3).

Reflection seismics is an important tool for thedetection of gas hydrate accumulations withinthe sedimentary column. These accumulationsare typically accompanied by a bottom simulating reflector (BSR) which marks the baseof the gas hydrate stability zone. The BSR has aphase polarity opposite to that of the seafloorreflection, indicating a high impedance contrastbetween the high p-wave velocity, gas hydrate-cemented sediments and underlying lowervelocity sediments that contain free gas. Whilegas hydrates within the bottom sedimentswere already discovered in 1974 by Russianscientists, we were the first to recognize theexistence of a BSR in the Black Sea (within theframework of GHOSTDABS).Our reflection seismic data demonstrate thatthe BSR is confined to a limited region of thestudy area (Fig. 1). It occurs within a waterdepth range of ca. 700 to 1500 m west of theDnieper Canyon and its maximum depthbelow the seafloor is ca. 440 m. Below a waterdepth of 1500 m, the BSR disappears. To compute the depth of the BSR, we used anaverage p-wave velocity of 1700 km/s for thesediment column down to the BSR depth asdetermined by a preliminary analysis of oneseismic refraction profile of subproject 5. Usingthe pressure-temperature stability conditionsat the base of the gas hydrate zone, the temperature at the BSR depth was estimated.This, together with the seafloor temperature,yields an average computed thermal gradientof 30 °C/km. This value is in good agreementwith published heat flow measurements usinga heat flow probe as well as drillhole measure-ments at DSDP sites (Leg 42B) in the centralBlack Sea.

Lüdmann T., Wong H.K., Konerding P.

Hamburg University, Institute of Biogeochemistry and Marine Chemistry, Bundesstr. 55, 20146 Hamburg, Germany

86

To estimate the possible volume of methaneassociated with the gas hydrate in the hydratestability zone and the amount of free gasbelow it within the study area, we mapped thespatial distribution of gas hydrates using theBSR and assumed an average thickness of thegas hydrate layer as well as the averageamount of free gas beneath 1m3 of gas hydra-te published for areas elsewhere. The order ofmagnitude of this volume is 102 km3.

Figure 1: Map showing the depth distribution in mbsf of the BSR (average p-wave velocity: 1700 km/s). Dotted lines indicate seismic tracks where the BSR could be observed. Inset shows the location of the study area.

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Biogeochemical turn over in methane richsediments at Hydrate Ridge, Cascadia Margin:Quantification using a model approach

At Hydrate Ridge, a part of the Cascadia convergent margin, active venting of fluidsand gases from the seafloor (SUESS et al.,2001) and abundant aggregates of bacteria inthe sediment (BOETIUS et al., 2000) and bacteria mats on the sediment (SUESS et al.,2001) has been documented. Moreover a largebiogeochemical dataset is avaiable from thislocation. This site is therefore a good exampleto study the processes in such an extreme environment with a numerical model to qualify and quantify them.Due to chemical interactions in the upper partof the sediments, only a very small portion ofthis methane reaches the ocean waters. This iscaused by anaerobic methane oxidation in thesediment e.g. (BARNES and GOLDBERG,1976), (MARTENS and BERNER, 1977), whichconsumes most of the upwardly diffusingmethane, before it can escape the sedimentsand contribute to water column and finally tothe atmosphere (CICERONE and OREMLAND,1988).The methane from below will be oxidized in this reaction (Formula 1) by a highlyspecialized archaeal-bacterial consortium(BOETIUS et al., 2000). The reaction occurs in asharp limited zone near the sediment surfacebecause sulfate from the overlaying seawater,that conduces as electron acceptor for themethane oxidation is present here. A result ofthis anaerobic reaction is the release of the by-products sulfid and bicarbonate into the porewater with the consequence of high concen-trations of them there.

(1)

The sulfid released from this reaction escapesfrom the sediment and represents the basis ofnutrition for benthic sulfid oxidizing bacteria atthe sediment surface, using oxygen and nitrate as electron acceptors. The massive amountof bicarbonate released during the methaneoxidation will increase the total alkalinity andsupports the precipitation of massive autigeniccarbonate/aragonite layers (Formula 2) in theupper sediment centimetres, that has beendescribed by (BOHRMANN et al., 1998).

(2)

The numerical early diagenetic model C.CANDI (LUFF et al., 2000) has been used tosimulate the biogeochemical processes in thesediments at Cascadia margin to describe thecomplex system in these specific sediments.Therefore the model, that originally based onCANDI by (BOUDREAU, 1996) has beenenhanced to ensure a realistic description ofthe thermodynamic processes in this environ-ment. Based on the new method to calculatethe thermodynamically controlled acid/baseequilibrium and using the individual transportof the species CO2, HCO3

– , CO32 – HS – and H2S

(LUFF et al., 2001) the model ensures realistic simulation of concentration profilesand therewith fluxes of these species betweensediment and bottom water. Moreover theadvanced thermodynamic description imple-mented in the model enables the quantifica-tion of carbonate dissolution and precipita-tion rates, even when sulfid in high concen-trations exist.

Luff R., Wallmann K.

GEOMAR Research Center for Marine Geosciences, Wischhofstrasse 1-3 D-24148 Kiel, Germany; rluff@geomar.de

88

Steady state approachBased on the steady state calculations, the carbon budget for this station can be estimated to demonstrate the tremendous turnover in the surface sediment evoked by theadvective methane transport from below.Figure 1 demonstrate the simulated carboncycle for a cold vent site in general and showthe carbon budget at the investigated site atthe southern summit of Hydrate Ridge. Thepicture is divided into a source part on the leftand a sink part on the right side. Carbon canreach the sediment at the surface in solid formof particular organic matter (OM) and in formof CaCO3. At the end of the simulated sediment column these species are allowed toleave the area, with the result of a net sinkrelated to the carbon budget. Moreover diffu-sive and advective fluxes of dissolved carbonspecies CO2, HCO3

-, CO32- and CH4 at the sedi-

ment - bottom water interface and also at theend of the sediment column affect the totalcarbon budget. Espeacilly the advective fluxesof dissolved species from deeper sediment layers represent a huge source of carbon in the surface part of these sediments.Dissolved organic matter that obviously alsoexist in nature has been neglected in themodel scheme of C. CANDI, all organic matterreach and leave the simulated sedimentcolumn in particular form. The general patternof the carbon budget of the surface sedimentat this site, shown in Figure 1 can be picturedout as follows:A strong flux of CH4 from deeper sedimentsconstitute the main source of carbon for thesystem, while the flux of HCO3

– between sediment and bottom water represents themain sink of carbon. The flux of CH4 out of thesediment at the surface is nearly zero. As alre-ady mentioned, bacteria in the upper few sedi-ment centimetres will consume the bulk ofmethane from below. The influx of CH4 andHCO3

– from below and the flux out of the sedi-ment at the surface of HCO3

– dominate thecomplete carbon system at this cold vent site.The fluxes of the solid species OM that nor-mally force the biogeochemical processes insediments and CaCO3 do not play a

significant role in this system (Figure 1). Thecarbon that reaches this sediment in form oforganic matter represents less then 8 percentof the total carbon budget, while the CaCO3

that leaves the sediment at the bottom in formof calcite and aragonite represents about 12percent.

Non steady state approachThe pore water fluxes measured by (TRYONand BROWN, 2001) have been used for a nonsteady state simulation of this station based onthe results of the steady state calculations.Their in situ fluid flow meter, that measures theflow by determining the degree of dilution ofa chemical tracer that is injected in the chamber (TRYON et al., 2001), has beendeployed for about 6 weeks on the northernand southern summit. The flow out of thesediment recorded on the southern summitwas very high, much higher than typicallyfound on mat sites (Tryon, pers. com.) withmaximum values of about 970 cm a– 1. Becauseof these constrained values we choose themore typically dataset measured on the nor-thern summit for the non steady state forcingof the model. In Figure 2 on top is the forcingfor this simulation, interpolated to daily values,shown. To demonstrate the reaction of thesediment to the changes in the fluid flow, thedistribution of Ca in the upper 5 cm and SO4

2 – in the upper 3 cm has been choosen. Thesteady state concentration distributions havebeen used as starting values for the non stea-dy state simulation. The model time step ofthis simulation has been chosen to one day.The moderate increase of the pore water fluxduring the first 15 days of the simulation isresponsible for stronger gradients of the pre-sented concentration distributions in the uppersediment. During this period the depth of the4 mmol l– 1 isoline decrease of about 1.5 cmand the sulfate penetration depth increase.The strong increase of the flow up to 240 cma – 1 between day 15 and 20 forces significant-ly stronger gradients in the concentrations.During this period the 4 mmol l– 1 isoline of Cahas been pushed by the flow up to about 1.5cm sediment depth and the SO4

2- penetration

89

depth incerases further on. Weaker fluxes afterday 20 from 150 and down to 75 cm a – 1 allowa decrease of the Ca gradients during the restof the simulation time, while the SO4

2-

penetration depth stays relatively constantabove 2 cm.This simulation clearly depicts the stronginfluence of the pore water velocity to the concentration distributions of the pore waterspecies. Within few days the species concen-trations and the gradients in the sedimentchange significantly only forced by the fluidflow. The strong dependencies between pore

water distributions and fluid flow also can beobserved in the concentration profilesSummerizing, the change of the advectionvelocity has large influence to the concentra-tion distributions of the solute species in thesediment. The concentration profiles of thesolid species, espeacilly CaCO3 concentration,that is also directly influenced by the changesin the fluid flow through the concentration ofCO3

2- or alkalinity, are not affected on thesimulated short times scales.

Figure 1: Carbonate budget of the first 15 cmof the sediment at this station, presented fluxes are in µmol cm– 2 a– 1

units. The overall carbonate turnoverestimated by the steady state approach at this station has beenestimated by the model to 1045µmol cm– 2 a– 1.

Figure 2: Top: Pore water fluxes at the sedimentsurface [cm a– 1] used as forcing forthe non steady state simulation of44 days to determine the responseof the sediment. The fluxes has beenmeasured by (TRYON and BROWN,2001), the measured values havebeen interpolated to daily values.Middle and bottom: Ca and SO4

2 –

concentrations in mmol l– 1 in theupper 5 and 3 cm respectively as aresult of the forcing.

90

LiteratureBarnes R. O. and Goldberg E. D. (1976) Methaneproduction and consumption in anoxic marinesediments. Geology 4(297-300).

Boetius A., Ravenschlag K., Schubert C. J.,Rickert D., Widdel F., Giesecke A., Amann R.,Jorgensen B. B., and Witte U. (2000) A marinemicrobial consortium apparently mediating ana-erobic oxidation of methane. Nature 407, 623-626.

Bohrmann G., Greinert J., Suess E., and Torres M.E. (1998) Authigenic carbonates from theCascadia subduction zone and thier relation togas hydrate stability. Geology 26(7), 647-650.

Boudreau B. P. (1996) A method-of-lines codefor carbon and nutrient diagenesis in aquaticsediments. Computers & Geosciences 22(5),479-496.

Cicerone R. J. and Oremland R. S. (1988)Biogeochemical aspects of atmospheric metha-ne. Global Biogeochemical Cycles 2, 299-327.

Luff R., Haeckel M., and Wallmann K. (2001)Robust and fast FORTRAN and MATLAB librariesto calculate pH distributions in marine systems.Computers & Geosciences 27, 157-169.

Luff R., Wallmann K., Grandel S., and SchlüterM. (2000) Numerical modelling of benthic pro-cesses in the deep Arabian Sea. Deep-SeaResearch II 47, 3039-3072.

Martens C. S. and Berner R. A. (1977) Interstitialwater chemistry of anoxic Long Island Soundsediments. I. Dissolved gases. Limnology andOceanography 22, 10-25.

Suess E., Torres M. E., Bohrmann G., Collier R.W., Rickert D., Goldfinger C., Linke P., Heuser A.,Saling H., Heeschen K., Jung C., Nakamura K.,Greinert J., Pfannkuche O., Trehu A.,Klinkhammer G. P., Whiticar M. J., EisenhauerA., Teichert B., and Elvert M. (2001) Sea floormethane hydrates at Hydrate Ridge, CascadiaMargin. Geophysical Monograph 124, 87-98.

Tryon M., Brown K., Dorman L., and Sauter A.(2001) A new benthic aqueous flux meter forvery low to moderate discharge rates. Deep-SeaResearch I 48, 2121-2146.

Tryon M. D. and Brown K. M. (2001) Complexflow patterns through Hydrate Ridge and theirimpact on seep biota. Geophysical ResearchLetters 28(14), 2863-2866.

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Deep microbial ecosystem: biogeochemicalcharacterisation and its potential substratefeedstock (Mallik Research Well 5L-38)

For many years conventional wisdom dictatedthat bacterial processes are restricted to thetop tens of metres in sediments, whereas processes in deeper layers and higher tempe-ratures are abiotic (Tissot and Welte, 1984).Recently, however, microbiologists and geo-logists have demonstrated that surprisingly largebacterial populations are present at least tohundreds of metres depth, and in this subsurface habitat there is considerable bacterial diversity (Parkes et al., 2000). The discovery of bacteria in both deep marine anddeep terrestrial sediments indicates the presenceof an ubiquitous and largely unexplored so-called “deep biosphere”. First assessments suggest its biomass to be approximately compa-rable to that of the Earth’s surface, thereby outlining the importance of this widely dissemi-nated hidden world for global geochemicalcycles and in this framework especially its role inthe formation of gas hydrate deposits and theuse of gas hydrates as a potential carbon source.

The Mallik Gas Hydrate Research Well 5L-38,which was drilled in Jan./Feb. 2002 at the northern edge of the Mackenzie River delta(Northern Territories, Canada) provides an exciting and rare opportunity to explore a deepmicrobial ecosystem in a terrestrial setting neara gas hydrate deposit using organic geo-chemistry. Our organic geochemical investiga-tions on this subject are addressed to 1) thespatial occurrence and nature of living bacteriain deep ecosystems, and to 2) processes andrates of substrate and nutrient release from theburied organic matter, which can be used as afeedstock for the deep biosphere.

Due to the fact that only a small part of viablemicrobial communities can be recorded bymicrobiological methods (Bachofen et al.,1998; Virtue et al., 1996), the use of specificbiomarkers, characteristic of those bacterialgroups, is an extremely promising tool foridentifying and quantifying deep microbialecosystems. In addition the stable carbon isotopic composition of single biomarkers willbe determined to provide crucial informationabout the carbon source and/or metabolic carbon fixation pathway utilized by its produ-cers. Both sediments and bacterial culturesfrom the Mallik Gas Hydrate Research Well willcome under detailed investigation.

Although it was shown that deep bacterialcommunities occur in the pore spaces of rockstheir carbon/energy sources and the mechanisms of substrate release remain stilluncertain. We wish to examine whether smallfunctionalised molecules (carbon dioxide, acetate, methanol etc.) and molecular hydrogen, utilisable by either syntrophs ordirectly by methanogens, may be generatednot only by primary biological processes (asknown from near surface environments) but byabiotic reactions in the sub-surface induced bythermal maturation processes. Were this to bethe case, deep bacterial activity could becomedecoupled from the surface biosphere and thebiotic primary degradation pathway, its ratebeing dependent upon the provision of substrate via abiotic chemical transformationsand transport processes in the geosphere. Toinvestigate this we will determine the yields ofindividual generated organic compounds usingkinetic and mass balance modelling and

Mangelsdorf K., Dieckmann V., Wilkes H., Horsfield B., and the Mallik working group

GeoForschungsZentrum Potsdam, PB 4.3, Telegrafenberg, 14473 Potsdam, Germany

92

relating the thermal lability of macromolecularsubstituents to biological origin using selectivedegradation followed by kinetic analysis ofresidues.

LiteratureBachofen, R., Ferloni, P., Flynn, I., 1998.Microorganisms in the subsurface.Microbiological Research 153, 1-22.

Parkes, R.J., Cragg, B.A., Wellsbury, P., 2000.Recent studies on bacterial populations andprocesses in subseafloor sediments: A review.Hydrogeology Journal 8, 11-28.

Tissot, B., Welte, D.H., 1984. Petroleum for-mation and occurrence. Springer Verlag,Berlin.

Virtue, P., Nichols, P.D., Boon, P.I., 1996.Simultaneous estimation of microbial phos-pholipid fatty acids and diether lipids by capil-lary gas chromatography. Journal ofMicrobiological Methods 25, 177-185.

AcknowledgementWe are grateful to the DeutscheForschungsgemeinschaft (DFG) for financialsupport (grant no. MA 2470/1-1).

Figure 1

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Structures and processes at methane seeps of the Black Sea

From June 28th to July 22nd the GHOSTDABS–cruise was realized south-west the Crimeapeninsula using the Russian RV PROFESSOR LOGACHEV and the German submarine JAGO (Fig. 1). The scientific partycomprised participants from the GHOSTDABSproject partners (Univ. Hamburg, GEOMARKiel, Univ. Göttingen, and FU Berlin), the co-operative projects MUMM (MPI Bremen)and OMEGA (GEOMAR, Kiel), and from international co-operation partners (Moscow,Sevastopol).At total, 120 stations were carried out during thecruise and allowed to meet the central scientifictopics of the GHOSTDABS Project:.- Localisation and investigation of gas

exhalations at the seafloor (vents, seeps,mud volcanoes) and associated structures(carbonates, bacterial mats).

- Inventory of gas hydrate occurrence.- Gas transfer: gas hydrates – sediment –

water column – atmosphere.- Biogeochemical transformation of gases

(methane).- Microbiological processes related to gas

hydrates and methane venting.Especially the surveys by the submersible JAGOyielded excellent samples and brilliant picturesfrom the sea floor. Thus we could discover afield of active gas seeps in these anoxic watersat 230 m water depth at a reef of up to 4 m high and 2 m wide structures arising from the sediment (Fig. 2). These structures consist of acm- to dm-thick microbial mat that is internallystabilized by carbonate precipitates. Firstresults show, that the carbonates, bulk biomass, and particular lipids all incorporatemethane carbon as indicated by their strongdepletions of 13C. Samples of the microbial

mats could be transferred home alive and arepresently object of various detailed investiga-tions performed together with the MUMMproject at the MPI in Bremen. They have beenfound to consist of densely aggregated methanotrophic archaea of the ANME-1 clu-ster and sulphate reducing bacteria(Desulfosarcina/ Desulfococcus group).The presence of a Bottom Simulating Reflector(BSR) in the Black sea sediments could beascertained for the first time by seismic investigation. First estimations of the distribu-tion of gas hydrates and the amount of incorporated methane are realized.

Michaelis W., Seifert R., and the shipboard scientific party of the GHOSTDABS cruise

Institute of Biogeochemistry and Marine Chemistry , University of Hamburg, Bundesstrasse 55,

20146 Hamburg, Germany

Figure 2

Figure 1

94

HDSD – Hydrate Detection and StabilityDetermination - A Tool For In-Situ Gas HydrateDestabilisation

IntroductionThere are two major limitations in the reserveestimations of near-surface gas hydrates:1) While seismic images, revealing the locationof the BSR, and vent phenomena are goodindicators for the occurence of shallow gashydrate thin sediment covers often prevent adirect observation.2) The limits of the in-situ PT field derived fromtheoretical models of the hydrate stability field(e.g. Sloan, 1990, Equiphase Hydrate (softwareby DBR International Inc., Edmonton, Alberta)differ considerably for a given hydrate depositand assumed gas composition. Hence theamount of energy needed to mobilize andextract gas from methane hydrate is onlyapproximately known.To address these limitations a new device isbeing developed within SFB 574 "Volatiles andFluids in Subduction Zones". This new tool,HDSD (Hydrate Detection and StabilityDetermination) will be capable of identifyingand quantifying near-surface hydrate layersthrough local heating and continuous thermaland resistivity profiling. The unit will be highlyflexible in its mode of operation due to a fullymodular configuration with easily exchangea-ble components.

Tool and OperationThe device is an add-on to the GEOMAR BenthicChamber Lander, an established and proventechnology for video-guided deployment andrecovery of benthic experiments. Initial sea tri-als of the HDSD will be carried out in Summerand Fall of 2002 during RV SONNE and RVMETEOR cruises. The initial HDSD configura-

tion for the first deployment comprises fourprincipal components:A rectangular in-situ experimenting chamberacting as a limiting thermal shield is slowly pushed into the sediment via a motor-drivenspindel to a depth of ~30 cm.An electric heating unit is mounted on theinner upper face of the experimenting chamber which consists of Konstantan coilsembedded in an isolating plastic carrier withan aluminum heat exchanger pointing towardthe sediment surface. Typical power ratings are50-100 W. The heating unit can be pre-programmed to generate a constant thermalfield. Energy is provided by conventional on-board batteries with a total capacity of up to1800 W. allowing operation times of 24-36hours.A central sensor carrier (sensor lance, 15 mmdiameter) is mounted vertically from the chamber top and is equipped with two rows ofminiature temperature and resistivity sensors,arranged in a vertical Wenner Array. The sensor arrays provide a fast and closely spacedvertical control of the migrating temperaturesignal and the resistivity response of hydratelayers within the experimenting chamber.A data logging and control unit is locatedabove the experimenting chamber and transfers time stamped sensor data to the flashmemory of the control unit.After deployment in its passive state, the sensor array monitors temperature and resistivity profiles and allows detailed insightsin the inhomogeneous structural relationshipof sediment and interfingering gas hydratelayers of the uppermost 30 cm below the

Mörz T. (1), Brückmann W. (1), Linke P. (1), Türk M. (1), Poser M. (2)

(1) GEOMAR Forschungszentrum für Marine Geowissenschaften, Kiel, Germany

(2) Oktopus GmbH, Hohenwestedt/Kiel, Germany

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seafloor. During this stage thermal equilibra-tion after the insertion of the chamber is documented. After the equilibration phaseambient temperature and resistivity profiles arerecorded. These profiles will then be used asreferences to quantify the time-dependent perturbation of the temperature and resistivityprofiles during subsequent heating. In its active stage, the heating unit will be used togenerate a steep temperature gradient to allowfor monitoring and determining the vertical thermal conductivity in various sediment typesand settings including hydrate bearing zones.Optional gas and fluid flow meters are monitoring and quantifying the amount of gasand fluid released during operation.

StatusIn early 2002 the HDSD heating unit was successfully tested in an 2.5 m 3 laboratory tankfilled with water and artificial sand/ bentonite sediment. During 24h experimentssediment temperature at a depth of ~30 cmwas raised by 5.5 °C with a steady state temperature gradient of 30 K/m.Additionally the vacuum mold and a first castof the sensor lance including all sensors werecompleted. Currently the data acquisition andcontrol unit is under development.The tool will be first deployed in July 2002during RV SONNE cruise 165 (OTEGA) toCascadia (Hydrate Ridge), were near-surfacegas hydrates are occuring in water depths between 600 and 800 m. Theoretical calcula-tions including real gas compositions and salinities indicate that a temperature increaseof 6°C should be sufficient to destabilize thesehydrate deposits. This well studied area there-fore represents ideal test conditions for thenew device. Later on HDSD will be used during SFB 574 todetect hydrates in the associated with mudvolcanoes, vents and pockmarks.

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Detailed Seismic Study of a Gas HydrateDeposit Offshore Costa Rica (DEGAS)

IntroductionGas hydrates are solid substances composed ofwater and gas molecules, mainly methane,which form under conditions of low tempera-ture and high pressure usually found in theupper few hundred meters of marine sedimentsin continental margins and in permafrostregions. In the context of energy resources, climate change and seafloor stability, gas hydrates have recently gained increasing scientific and industrial interest. Anyhow, estimates of the global amount of carbon ingas hydrates, about 10 teratonnes followingrecent estimates (Kvenvolden, 2001), arebased on sparse direct observations from drilling. In seismic sections the base of the gashydrate stability zone is often associated withbottom simulating reflectors (BSRs). In thisregard, the enhanced evaluation of remotesensing methods (e.g. seismic techniques) tomap and to quantify gas hydrate and free gascontent has the potential to improve quantifi-cation of local and global amounts of gas asso-ciated with gas hydrates.

Survey Area & New Seismic DataBSRs imaged on reflection seismic lines alongthe Pacific continental margin of Costa Ricaare characterized by diverse rather than uniform occurrence. Southwest of NicoyaPeninsula continuous BSRs are observed bet-ween water depths of about 600 m on theupper margin and 4000 m at the MiddleAmerica Trench (MAT). North of the so calledfracture zone trace, in the area of ODP-Leg170, no BSRs are observed, presumably relatedto the unusually low heat flow in this area(Kimura et al., 1997). Southeast of NicoyaPeninsula BSRs are characterized by patchyoccurrence. In this region, within a 450 km2 3-

D reflection seismic survey area (Hinz et al.,1992), which is located about 10 km landwardof the MAT, BSRs are imaged in an area ofabout 20 km2. To investigate the patchy occurrence and to quantify the amount of gashydrate and free gas present in the sediment,eight 2-D high resolution long offset (5250 m)reflection seismic lines have been acquired in1999 across the 3-D survey area to providecontinuous wide angle data (Fig. 1).

Methods & First ResultsIn these post-stack seismic sections BSRs areimaged at about 300 m below seafloor bet-ween water depths of about 600 and 3000 m.Faults are observed at and below BSR depthsproviding pathways for vertical migration andaccumulation of methane-rich fluids. Analysisof the variation of pre-stack reflection amplitudeversus angle of incidence (AVA) is implementedto extract acoustic parameters of gas hydrate-and free gas-saturated sediments at the BSR.Prominent variations of post-stack and pre-stack zero-offset reflection amplitudes areobserved along the seismic lines, which pre-sumably reflect varying concentrations of gashydrate and/or free gas. BSR reflections show aclear phase reversal against the seafloor reflection, and source-receiver offsets that arefive times the target depth provide incidenceangles up to 70°. Due to the lack of any wellcontrol in the immediate vicinity of the mainstudy area, high resolution semblance-basedvelocity analyses constrains AVA modeling. Torestore amplitudes at the BSR, source andreceiver directivities are explicitly considered.Amplitude analyses performed at selectedpoints along seismic lines with high S/N ratioBSR reflections show pronounced class III AVAanomalies with strong negative zero-offset

Müller C., Bönnemann C., Neben S.

Bundesanstalt für Geowissenschaften und Rohstoffe, Stilleweg 2, 30655 Hannover, Germany

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reflection coefficients that increase with offset.In combination with forward modeling (fullZoeppritz) a differentiation between locationscharacterized by the solely presence of hydrateand locations characterized by the solely presence of free gas or free gas associated withgas hydrate (Fig. 2) is indicated. Present differen-tiation is based on the AVA trend at intermedia-te angles of incidence (~30°-60°), while curvesare hardly distinguishable at lower angles andS/N ratio rapidly decreases at far offsets, due tointerference at the BSR reflection.

ReferencesKimura, G., Silver, E., Blum, P., et al., 1997,Proc. ODP, Init. Repts., 170: College Station,TX (Ocean Drilling Program).

Kvenvolden, K.A. and Lorenson, T.D., TheGlobal Occurrence of Natural Gas Hydrate, inNatural Gas Hydrates: Occurrence, Distribu-tion, and Detection, edited by C.K. Paull andW.P. Dillon, pp. 3-18, AGU monograph series,124, 2001.

Hinz, K., and Scientific Crew: Geoscientificinvestigation off Costa Rica, Pacomar II,Archiv-Nr. 110148, BGR internal report, 1992.

Figure 1: Wide-angle reflection seismic lines are located across the 3-D survey area offshore Costa Rica to determine acoustic properties at the BSR from AVA analyses.

Figure 2: BSR AVA curve extracted from CMP 4500, line BGR99-60,indicates the presence of free gas (reduced Poisson’s ratiomodel).

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Massive Structures in the anoxic Black Sea:Biomass and carbonate formation based onthe anaerobic oxidation of methane

Active gas seeps occur at water depths bet-ween 35 and 800m on the northwestern shelfof the Black Sea, off the Crimean Peninsula.This methane seepage into the water columnmakes this an interesting site for the investiga-tion of methane oxidation, especially theanoxic zone (below approx. 130m waterdepth) where it is most likely anaerobically oxidized. Using the submersible “Jago” fromaboard the Russian research vessel “ProfessorLogachev”, we explored the seafloor of thearea. At the depth of about 230 m at 44°46´N,31°60´S massive structures of biomass and carbonates were discovered above activemethane seeps. The almost pure microbial biomass inside of these structures was up toseveral centimeters thick and in close associa-tion with precipitated carbonates. Experimentswith radiotracer were performed on board ofthe ship. Living samples from the mats wereincubated under strictly anoxic conditions andtaken to the home laboratory to study themolecular identity of the organisms and thephysiology of the anaerobic oxidation ofmethane (AOM). Carbon isotopic analysis revealed strong deple-tions of 13C in the bulk biomass as well as inparticular lipids (Michaelis, W. personal communication). Therefore the organismsseem to produce their biomass directly fromthe strongly depleted methane. 13C depletionsin the carbonate structures point towards aclose coupling of biological activity and carbonate precipitation.In short-term incubations sulfate reduction and

methane oxidation were quantified by radiotracer studies. At high methane concen-trations these processes apparently take placeat a ratio close to 1:1 (Fig. 1). In long-termincubations with mat samples, methanedependent sulfide production from sulfate wasdemonstrated. This is the second time that theprocess of AOM could be shown in vitro(Nauhaus et al. 2002). High sulfide productionrates (31 µmol d–1 g–1 dry weight) occurred withmethane as the only carbon source and elec-tron donor. In controls without methane nosulfide production occurred (Fig. 2). It is belie-ved that AOM is accomplished by two orga-nisms, one of them being a methanogen ope-rating in reverse (oxidizing the methane) andthe second one being a sulfate reducer.Support of this theory so far has come frommolecular studies, which showed that most ofthe biomass in the mats is composed ofarchaea (ANME-1 cluster) and sulfate reducingbacteria (Desulfosarcina/Desulfococcus group).Thermodynamic calculations show that theamount of energy gained by this metabolism isquite low (-24 kJ mol –1 CH4) and has even to beshared between the two organisms. Growthrates are therefore expected to be low.Nevertheless with the use of radiolabeldmethane and a beta-Micro-Imager we wereable to show carbon incorporation into micro-bial biomass.

Nauhaus K. (1), Treude T. (1), Gieseke A. (1), Knittel K. (1), Boetius A. (1, 2), Michaelis W. (3), Widdel F. (1)

(1) Max-Planck-Institute for Marine Microbiology, Celsiusstr. 1, 28359 Bremen, Germany

(2) Alfred-Wegener-Institute for Polar and marine Research, 27515 Bremerhaven, Germany

(3) University of Hamburg, Institute for Biogeochemistry and Marine Chemistry, Bundesstr. 55, 20146 Hamburg,

Germany

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Figure 1:Stoichiometry of sulfate reduction (SR) and anaerobic oxidation of methane (AOM) determined in radiotracerexperiments, using two methane concentrations.

Figure 2:Sulfide production with methane as the only electrondonor (filled symbols), control without methane (opensymbols) over an incubation period of 60 days.Columns represent sulfate reduction rates (n=6) with and without methane.

FoundationsSamples were optained during the Black Sea cruise within the program GHOSTDABS.Laboratory studies were performed within the program MUMM.

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Biomarker evidence of methane oxidation insediments of Haakon Mosby Mud Volcano

Undisturbed sediment cores recovered duringcruise Atalante 2001 at the Haakon MosbyMud Volcano (HMMV) from four different sites(thermal Center, Pogonophora dominatedarea, Beggiatoa dominated area and a referen-ce station) were for the first time investigatedfor biomarker signatures and their associatedd13C-- values. Preliminary results demonstratethat anaerobic subsurface sediment samplesfrom the biologically active areas are typicallyenriched in the overall content of bacterial andarchaeal lipids directly indicating a high micro-bial biomass. Moreover, concentrations of spe-cific fatty acids (cis11C16:1), ether lipids (archae-ol, hydroxyarchaeol, sn2hydroxyarchaeol), andhydrocarbons (pentamethyicosane (PMI):4,PMI:5) that are commonly found in

environments characterized by anaerobic oxi-dation of methane (AOM) [1, 2, 3, 4] areapproximately 3 to 150-fold higher comparedto the reference site. Highest lipid concentra-tions were encountered at one site where sul-fur oxidizing Beggiatoa densely cover the sedi-ment. Iincreased concentration of AOM speci-fic biomarkers in the upper most cm comparedto deeper layers of the sediment (Fig.1) showthat microbial AOM activity is restricted to thesubsurface horizon while the deeper layersremain inactive. Small increments may, howe-ver, indicate a second “hot spot” of AOM indeeper layers. In contrast, AOM biomarkerswere minor in sediments of the thermal centerand the Pogonophora dominated site wherelipid analysis suggests the dominance of

microbial processes other than AOM, mostprobably aerobic methanotrophy. In the nearfuture, carbon isotope analyses should providecomprehensive evidence of the dominant

methanotrophic character at the base of thefood web at HMMV. Our findings are in verygood agreement with direct counts of AOM-performing syntrophic consortia that consistsof archaea and sulfate reducing bacteria [5].

References[1] R. D. Pancost, et al., Applied and Environ-mental Microbiology 66, 1126-1132 (2000).

[2] K.-U. Hinrichs, R. E. Summons, V. Orphan,S. Sylva, J. M. Hayes, Organic Geochemistry31, 1685-1701 (2000).

[3] M. Elvert, Ph.D. thesis, Christian-Albrechts-University of Kiel (1999).

[4] M. Elvert, J. Greinert, E.Suess, M. J. Whiticar,in Natural gas hydrates: Occurrence, distribu-tion, and dynamics C. K. Paull, W. P. Dillon,Eds. (American Geophysical Union,Washington DC, 2001), vol. 124, pp. 115-129.

[5] A. Boetius, et al., Nature 407, 623-626(2000).

Niemann H., Elvert M., Boetius A.

Max Planck Institut für Marine Mikrobiologie, Bremen, Celsius Straße 1, 28359 Bremen, hniemann@mpi-bremen.de

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Figure 1:(b enlargement of a): Depth profile of AOMspecific biomarkers (alcohols: archaeol,sn2hydroxyarchaeol; hydrocarbons: PMI:4,PMI:5; fatty acids: cis11C16:1)in µg/gdw at aBeggiatoa site . Increased concentrations indicate high anaerobic oxidation of methanein the subsurface layer.

a)

b)

Tectonically induced migration of the sulfate-methane-reaction zone in marine sediments of the Sea of Marmara - a case study

A common characteristic of many continentalmargin sedimentary deposits is that sulfate(SO4

2-) with seawater concentration penetratesseveral meters to more than 100 meters downinto the sediment porewater. The sulfate willbe reduced to H2S, in general, by oxidation oforganic matter mediated by the activity of sulfate-reducing bacteria [1]. The sulfate concentrations in the sedimentary porewatersshow constant or continuously decreasing gradients from the surface down to the sulfate-reduction zone where the sulfate pool becomes completely exhausted and methane(CH4) concentrations are high in the underlyingpore space. Thus, the anoxic methane oxida-tion is the basic process which creates the che-mical potential for the sulfate reduction [2]. However, changes in this gradient have been

observed several meters below the surface insediment cores from different locations; anoxicsulfide oxidation in surface layers and non-local transport mechanisms of porewater orsubmarine landslides have been mentioned tobe responsible for porewater gradient changes[3, 4]. Our studies of a sediment core from theMarmara-Sea also show a remarkable changein this gradient. The results indicate that along-term constancy of diagenetic processescannot be assumed at all times. Methane emanations from the seafloor as observed atother locations along the deeper Ganos Faultgive evidence that the sulfate-methane-reaction zone (SMRZ) already reached the sediment water interface [5]. We thereforesuggest an evolution of a time-dependenttransient state for this reaction zone.

Reichel Th. (1), Halbach P. (1), Holzbecher E. (2)

(1) Free University of Berlin, Dept. for Geochemistry, Hydrogeology, and Mineralogy, 12249 Berlin, Germany.

hbrumgeo@zedat.fu-berlin.de, thomasr@zedat.fu-berlin.de, rmoche@zedat.fu-berlin.de

(2) Institute of Freshwater Ecology, Department of Eco-Hydrology, 12587 Berlin, Germany, holzbecher@igb-berlin.de

Figure 1:An overview of the work-location in the MarmaraSea (left). The local tecto-nic situation and the posi-tion of core KLG 72 areshown in the pictureabove.

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The subject of our study is to show that suchchanges could be caused by tectonic activity(e.g. earthquakes) if they influence the respec-tive flux of one of the involved reaction partners. For this purpose we present datamainly from one gravity core (72 KLG) whichwas recovered from the Ganos Fault, a tectonically very active fault zone in the Sea ofMarmara (Fig. 1).

The results from this sediment core revealed aporewater pattern which can be subdividedinto four different sections (Fig. 2):1) a relic steady-state diffusion zone

in the upper part of the core2) a transition zone where sulfate

decreases with a steeper gradient3) the sulfate-methane-reaction zone and4) the methane-supply zone. Our study starts with a steady-state concentra-tion profile for sulfate, which is then graduallyconsumed by a front of rising methane causedby an oversupply of this gas. From the sulfateconcentrations measured in the upper 3 m ofthe core (with a high correlation coefficient of0.98) a linear steady-state profile results which,after extrapolation, reaches zero concentrationat a depth of 32.2 m. This is equivalent to agradient of 0.101 g/l · m (0,1 mmol/l · dm) forsulfate.

It is assumed that after an extraordinary event(earthquake) the methane flux increasedremarkably, reached that toe-point and, reacting with sulfate in the SMRZ, which hasgradually been rising upward since that time. The transport mechanisms within the sedimentcolumn for methane is advection, whereas sulfate is transported by diffusion. Implemen-tation of this data-set into a computer baseddiffusion-advection model estimates a velocityof 1.8 cm/a for the SMRZ-rise. The determinedtime period for the SMRZ to cover the distancefrom 32.2 m to the current position (~ 4-5 m)is 1550 years.Many earthquakes have been reported in theBosporus region which could possibly haveaffected the Marmara Sea as well and thusopened new pathways for the rise of methanefrom the deeper subsurface [6, 7]. One majorevent within the Marmara Sea is well documented in 447 a.D.; this is almost identical to the initial time of 450 a.D. as calculated by our model. The epicentre of theearthquake lay in the direct vicinity of the sitewhere our core was taken. The remarkable factthat our modelled time frame coincides withthe date of a large local earthquake leads theauthors to believe that the SMRZ migrationcan indeed be initiated by tectonic events.

Figure 2:Concentration profiles of SO4

2- and CH4.In (1) SSDZ = relic steady-state diffusion zone, TZ = transition zone,SMRZ = sulphate-methane-reaction zone, MSZ = methane-supplyzone. In (1) the TZ is characterized by a steepdecrease of the sulfate-concentration; the methane-concentrations insteadincrease drastically withinthe SMRZ [2].

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References[1] Widdel F. (1988) Microbiology and ecologyof sulfate- and sulphur reducing bacteria. In: Biology of Anaerobic Microorganisms (ed.Zehnder A.B.J.). Chap. 10, pp. 469-585, JohnWiley & Sons, NY.

[2] Niewöhner C., Hensen C., Kasten S., Zabel M., Schulz H.D. (1998) Deep sulfatereduction completely mediated by anaerobicmethane oxidation in sediments of the upwelling area off Namibia, Geochim.Cosmochim. acta, 62, No. 3, 455-464.

[3] Fossing H., Ferdelman T., Berg P. (2000)Sulfate reduction and methane oxidation incontinental margin sediments influenced by irri-gation (South-East Atlantic off Namibia), Geo-chim. Cosmochim. Acta, 64, No. 5, 897-910.

[4] Zabel M. and Schulz H.D. (2001)Importance of submarine landslides for non-steady-state state conditions in porewater systems - lower Zaira (Congo) deep-sea fan, Marine Geology, 176, 87-99.

[5] Halbach P. , Kuscu I., Inthorn M., Kuhn.T,Pekdeger A., Seifert R. (2001) Methane insediments from the deep Marmara Sea and is relation to local tectonic structures, in:N.Görür (Ed.), NATO advanced ResearchPapers: integration of earth sciences researchon the 1999 Turkish and Greek earthquakesand needs for future cooperative research,TÜBITAK, Istanbul, (in print).

[6] Ambraseys N.N. and Finkel C.F. (1991)Long-term seismicity of Istanbul and of theSea of the Marmara Sea region, Terra Nova,3, 527-539.

[7] Stiros St.C. (2001) The 365 AD Creteearthquake and possible seismic clusteringduring the fourth to sixth centuries AD in theEastern Mediterranean; a review of historicaland archaeological data, Journal of StructuralGeology, 23, 545-562.

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Methane-derived carbonate mineralisation inthe northwestern Black Sea

During the GHOSTDABS expedition with RVLogachev in July/August 2001, methane seepsat the shelf and slope of the northwesternBlack Sea were investigated. Seep areas closeto the Dnepr Canyon were found to be sites ofintense carbonate deposition. In the oxic zone of the shelf and upper slope,carbonate precipitation is confined to theanoxic sediment where layered carbonatecrusts and flat plates form. Here, seepageinduces intergranular precipitation of microcry-stalline high-Mg-calcite and aragonite. Thecemented siliciclastic sediments may containmytiloid or dreissenoid bivalves and carbonateconcretions that consist of displacing elongated aragonite crystals. At about 180 m water depth, in the upperanoxic zone of the slope, widespread large carbonate plates occur. Small irregular chimney-like structures arise from these basal plates.Carbonate plates are tilted and broken,obviously due to strong erosional forces ofcoastal currents in this water depth. Within the deeper permanent anoxic slope,chimney-like build-ups are found that arepenetrated by active seepage. During the‘Jago’ submersible dives down to a depth of400 m, towers up to 4 m in height have beendiscovered. The carbonate minerals forming thechimneys are high-Mg-calcite and aragonite.High-Mg-calcite occurs in a microcrystallinevariety (micrite) containing 11 to 14 mol%MgCO3. Aragonite mostly forms fibrous cementcrystals as isopachous layers or botryoids(Peckmann et al. 2001). Microcrystalline arago-nite is less common. The exterior surfaces ofthe chimneys mostly consist of aragonitecement, indicating that aragonite preferential-

ly forms in contact with seawater. The chimneys internal fabric is patchy with highlyirregular transitions from micrite clusters toaragonite cement. A volumetrically significantportion of the chimneys is represented by irregularly distributed, inter-connected porespace, but no central channel exists. The carbonates are extremely depleted in 13C.Stable isotope analyses yielded δ13C values thatrange from -27 to –41‰ PDB for high-Mg-cal-cite and from –26 to –38‰ PDB for samples ofaragonite cement. These low δ13C values reve-al that the carbonates predominantly derivefrom the microbial oxidation of methane. The chimneys exterior surfaces, internal cavitywalls, and veins are heavily colonised by themicrobial consortium that presumably performs anaerobic methane oxidation.Features of the exterior surface areas at the toppart of many chimneys are hollow spheres.Their walls consist of a thin, porous layer ofaragonite, which is covered by a black microbi-al mat. Initially hollow spheres in older portionsof chimneys tend to be filled by authigenic carbonates from the aragonite wall towardsthe interior. When sampled with the submersible, the hollow spheres have been found to be partlyfilled by gas. Due to the spherical shape, thecolonisable surface is maximised. Substratumfor microbial metabolism, methane, is providedfrom the interior of the sphere, and exchangewith seawater, which is important for e.g. thesupply of sulphate, can proceed most efficiently.δ18O values of the carbonates, ranging from+2.0 to +0.2‰ PDB, are rather close to δ18 Ovalues of dissolved seawater bicarbonate (Leinet al., 2002), and 87Sr / 86Sr ratios of microcry-

Reimer A. (1), Peckmann J. (2), Reitner J. (1)

(1) Geowissenschaftliches Zentrum der Universität Göttingen, Abteilung Geobiologie,

Goldschmidtstraße 3; D-37077 Göttingen, Germany

(2) Postgraduate Research Institute for Sedimentology, University of Reading, Whiteknights, Reading, RG6 6AB, UK

stalline carbonate (mean 0.70927) and arago-nitic cement (mean 0.70918) indicate that Sr isderived from the ambient seawater (mean0.70917) and not from seepage fluids.The methane seeps in the northwestern BlackSea are sites of a pronounced biogeochemicalcycling of carbon. The carbonates as productsof microbially mediated reactions exhibit signa-tures of both deep-seated and marine sources.

ReferencesPeckmann J, Reimer A, Luth U, Luth C,Hansen B T, Heinicke C, Hoefs J, Reitner J(2001) Methane-derived carbonates andauthigenic pyrite from the northwestern Black Sea. Marine Geology 177, 129-150.

Lein A Y, Ivanov M V, Pimenov N V, Gulin M B(2002) Geochemical Characteristics of thecarbonate constructions formed during microbial oxidation of methane under anaerobic conditions. Microbiology, 71, 1, 78-90.Translated from Mikrobiologiya, 71, 1, 89-103.

Figure 1:Sketch of a carbonate chimney from the permanentanoxic zone of the northwestern Black Sea slope. Notice black spherical structures on top of the chimney.Height of the Chimney is appr. 1.5 m.

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107

An Introduction to INGGAS: INtegratedGeophysical characterisation and quantification of GAS hydrates.

The quantity and the distribution of gas hydrates along the continental margins hasimportant implications for slope stability, for climate change, for offshore engineering andpotentially for future energy resources.However, the main method for remotely deter-mining the presence of gas hydrate remainsthe imaging of a bottom-simulating reflection(BSR), although this only indicates the presenceof hydrate where it is underlain by free gas.Furthermore, the distribution of hydrate volumes within the sediment has importantimplications for the shear strength of the sediment. Finally, the fluid flow regime associated with hydrate formation and dissoci-ation remains poorly understood. To address

these issues, the INGGAS project set out todevelop geophysical equipment necessary toinvestigate - the nature, structure, distribution and quan-

tification of gas hydrate fields in all waterdepths and methane-bearing permafrostsoils in shallow water environments.Questions of interest include the reservoircharacteristics of gas hydrate bearing sedi-ments and the underlying free gas zone, thethickness of the transition between them,the rate at which this equilibrates, theamount of free gas present beneath it andhow gas hydrates can be identified in theabsence of a BSR.

- physical properties (P- and S-wave velocities,

Reston T. (1), Gajewski D. (2), Hübscher C. (2), Flüh E. (1), Bialas J. (1), Villinger H. (3), Theilen Fr. (4),

and the INGGAS Group

(1) GEOMAR Research Centre, Kiel, Germany

(2) University of Hamburg, Germany

(3) University of Bremen, Germany

(4) Christian-Albrechts University, Kiel, Germany

Figure 1:Schematic illustration showing how the equip-ment developed withinINGGAS can be used forinterdisciplinary investiga-tions of gas hydrates. Toavoid confusion, only mainlinks are shown.

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shear moduli) of sediments within andbeneath the gas hydrate zone. This has implications for the amount and distributionof gas hydrates and of free gas and also forslope stability.

- the different physical, sedimentological andtectonic environments in which gas hydratesdevelop and accumulate. Parameters inclu-de methane flux, heat flux, water depth, deformation rates and fluid flow rates(hence pore pressure).

INGGAS consists of five integrated Subprojects(Figure 1): 1) INGGAS-HISS. This set out to develop an integrated seismic system for gas hydrate research. The key aspects are the use of oceanbottom sources to generate the shear wavesneeded to determine, in conjunction with P-waves, the physical properties of the hydratedand the free gas zone. Two different oceanbottom sources were successfully testedduring a cruise with the RV Sonne in March2002. This will reveal the amount and distri-bution of both gas hydrates and free gas within the sediment, and will allow assessmentof the influence of gas hydrate and the under-lying gas zone on slope stability. The Sub-project also will acquire a high frequencytowed source (a watergun) for high resolutioninvestigations of hydrates.2) INGGAS-OBS This Suproject has construc-ted and tested the 3-C ocean bottom seismo-meters needed for multi-component oceanfloor seismology, and in particular the recor-ding of S-waves. These will in conjunctionwith more traditional P-waves, allow the physi-cal properties of the subsurface to be fully cha-racterised, revealing the amount and distribu-tion of gas hydrates within the sediments inthe interwell gap. Testing of the instrumentshas taken place offshore Spitsbergen in twoplaces where gas hydrates are known to exist(one with a BSR, one without), offshore Peru inMarch 2002, and will further take place offNorway in Summer 2002.3) INGGAS-DEEP TOW: This Subproject hasdeveloped a deep-towed streamer system

rated for ocean depths. Lowering the strea-mer to the seafloor, reduces the size of theFresnel Zone and hence increases the spatialresolution. Previous studies have shown thebenefit of such systems for imaging small-scalestructures such as faults that are likely to beimportant fluid conduits, and for revealing thefine structure of the BSR. The streamer hasbeen successfully tested off Peru in March2002 (see contribution from Breitzke andothers). Incorporated within the deep towsystem is a navigation system rated for oceandepths, allowing accurate location of the stre-amer. This navigation system can also be usedfor the side-scan sonar to be acquired withinthe OMEGA project.4) INGGAS-FLUX: This Subproject set out todevelop and construct low-cost disposablepore pressure probes and an extended heatflow probe. Both are essential to characterisethe fluid flow regime associated with gashydrates, particularly in regions of active defor-mation. After data collection, the pore pressu-re probe will release a data logger to the sur-face, from where it will transmit the data viasatellite link to the lab. The extended heatflow probe (up to 6 m penetration) will impro-ve heat flow measurements needed to deter-mine fluid outflow rates. As gas hydrates formfrom gas and water rising from depth, under-standing the fluid regime of gas hydrates is apre-requisite for understanding gas hydrateformation. 5) INGGAS-NATLAB: This subproject is concer-ned with the study of shallow gas-bearingsediments in the Baltic Sea using some of thegeophysical techniques similar to those withinthe rest of INGGAS. In particular, the mainobjective of the project is the assessment ofshear waves in the sea floor under in-situ conditions and the correlation of shear wavevelocities with sediment properties. The shearwave velocity measurements are based onScholte waves, which are also observable inthe lower part of the water column and thusassessable by a continuously towed streamerjust above the sea floor.

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Raman Spectroscopic measurements of gas hydrates

The knowledge of the conditions for gashydrate formation, as well as their stabilityfields and phase boundaries are necessary fortheir fundamental understanding. The forma-tion of pure gas hydrates under various P-T-x-conditions and the phase diagrams of thesesystems are well known, whereas phase diagrams of mixed gas hydrates based onexperimental data have not been publishedyet. Mixed clathrates behave different from thepure endmembers and calculated phase relationships often deviate considerably fromexperimental data. Therefore, the aim of ourresearch project is to synthesise and analysemixed gas hydrates and use the experimentaldata obtained for the construction of phasediagrams. For these purposes an experimentalset-up has been developed, which allows theobservation and documentation of the formation, growth and decomposition ofmixed gas hydrates as well as the analysis ofthe gaseous and solid phases under approached equilibrium conditions via RamanSpectroscopy for the determination of thephase composition.

The main item of the experimental device isthe pressure cell (Fig. 1), which can be used inthe temperature range between –27 °C and +80 °C and in the pressure range between 0.1and 10.0 MPa. The small sample volume (0,4 cm3) and the all-around cooling of thesample obviate a gradient of temperature. A quartz window permits the analysis of thephases by Raman Spectroscopy and the obser-vation of the sample in the cell or the docu-mentation of formation or decomposition pro-cesses with a CCD-camera.

For testing the functionality of the experimentalset-up the well known system methane-waterhas been chosen. The shift of the peak position,the split of the band and the broadening ofthe band enable a clear identification ofmethane trapped in the clathrate lattice [1].Preliminary results in the system CH4-CO2-H2Oindicate that also CO2 gets incorporated into ahydrate lattice and the bands are broadenedand the peak position shifts similarly (Fig. 2).

Schicks J., Lüders V., Möller P.

GeoForschungsZentrum Potsdam, AB 4, Telegrafenberg, 14473 Potsdam, Germany

Figure 1

Figure 2

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Multitudinous measurements under variableconditions are necessary to construct a phasediagram: at constant gas composition andtotal pressure the temperature is varied andthe establishing composition of gas and solidphases are registered. The results obtained forthe system methane-water correspond well toliterature data [2] (Fig. 3).

In addition to the actual measurements on thesystem CH4-CO2-H2O the systems CH4-N2-H2Oand CH4-H2S-H2O will be studied systematical-ly with the aim to determine the clathrate-soli-dus as a function of the gas composition, thesalinity of the aqueous phase, pressure andtemperature.

References[1] Subramanian, S; Kini, R.A.; Dec, S.F.;Sloan, E.D.; Chemical Engineering Science 55;2000;1981-1999

[2] Sloan, E.D.; Clathrate Hydrates of NaturalGases; Marcel Dekker,Inc.;1997; New York,Basel

Figure 3

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Development of a Methane Biomicrosensor for Deep Sea Applications

The main objective of this project is to adaptan existing methane biomicrosensor for deepsea applications. Microsensors are needle shaped glass electrodes with a sensitive tip of1-20 µm diameter, depending on the type. Inthe conventional microsensors, the analyte isspecifically and directly detected by ampero-metric or potentiometric means. In biosensorsan extra step is involved: the conversion of thesubstrate by bacteria immobilised in the sensortip. Methane detection using a biosensor isbased on the co-conversion of oxygen bymethane oxidizing bacteria (CH4 + O2 -> CO2 +H2O) and change in oxygen concentration ismeasured with an integrated oxygen sensor.The methane biomicrosensor (Fig. 1) consistsof three parts: an oxygen microsensor and twoglass capillaries. The inner glass capillary servesas oxygen reservoir and the outer capillary con-tains methanotrophic bacteria.

The sensor is based on a counterdiffusion principle. Methane oxidizing bacteria placed inthe outer glass capillary utilize oxygen from theinternal oxygen reservoir when methane fromthe exterior diffuses through the tip membrane.The external partial pressure of methane deter-mines the rate of bacterial oxygen consump-tion within the sensor, which in turn is reflected by the signal from the oxygen microsensor. The higher the external partialpressure of methane, the more oxygen thebacteria consume, subsequently a lower signalis measured (Fig. 2).

Schmidt-Brauns J., de Beer D.

Max-Planck-Institute for Marine Microbiology, Bremen, Germany

Figure 1:Schematic drawing of a methane biomicrosensor. Left: entire sensor; Right: tip section. From Damgaardand Revsbech, 1997.

Figure 2:Functioning principle: The partial pressure of oxygenmeasured in the two situations is indicated by thearrows. The sensor is exposed to a high (A) or low (B) partial pressure of methane.

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Deep sea (100-1500 m) biosensor manufactu-re and use will have to account for changes inpressure in temperature. Pressure will affect mainly the inner gas filledcapillary. A new initiative to make this capillarypressure resistant will be to fill the capillarywith oxygen saturated silicon oil instead ofpure gas. Low temperatures at working depths will resultin a reduced bioreactive sensitivity of mostmethanotrophic bacteria. A second initiative isto utilize Methylosphera hansonii, a psychro-philic aerobic methane oxidizing species whichwas isolated from a seawater lake in Antarctica.Another possibility to overcome the tempera-ture problem is to enlarge the reaction zoneinside the biosensor to allow more conversion.

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Simulation of the oceanic gas hydrate removal using the mammoth-pump-principle

Conceptual formulation and goal of this studyWithin the scope of a financially supportedresearch project (BMBF/Project 03G0550A),the task is to develop a computer-program todescribe the destabilsation and controlledextraction of oceanic gas hydrates. The feasibility of controlled upflow of destabilisedgas hydrates by the mammoth-pump principlein concentric tube arrangements is the mainobjective of the study. Basic aspects of gashydrate destabilisation and flow mechanismsare considered. The feasi-bility and process safety are points of interest.The examination is based on realistic data andnumerical simulations. A software code will bewritten for the simulation of the steady stateand the dynamic process operation.

IntroductionIn the last years, the gas hydrate topic is ofrising economical and ecological interest. Onthe one hand, the controlled use of gas hydrates as a ressource could guarantee theworldwide energy supply for a long time. Onthe other hand, the instability of this ressourcedepicts an exposure, i.e. an uncontrolled, climate affecting release of gas (hydrocarbons,mainly methane) from gas hydrates has to beavoided. Because of this, the controlled extraction of gas hydrates is not only of eco-nomical interest but also of ecological andsocietal relevance in view of the preventive, climate-saving removal of instable hydratefields.

Description of the extraction apparatusThe main research objective is the feasibility ofapplying the mammoth-pump-principle to the

controlled and safe upflow of instable oceanicgas hydrates and hydrocarbons, respectively.The main elements of this approach are:- thermal stimulation of gas hydrates in

oceanic sediments with heated sea-water torelease hydrocarbons,

- concentric tube arrangement for the purposeof transporting heated sea-water in the innertube and mixtures of water, hydrate particles,sediment and gaseous hydrocarbons in theouter an-nulus by the mammoth-pump-principle.

Figure 1 shows a sketch of the principle. Thermalstimulation with heated sea-water to releasehydrocarbons from instable gas hydrates,particularly methane, is the method of choi-ce for the technical approach. The mainadvantages are: - no additional chemicals are required,- the necessary transport of energy to the

deposit can directly be integrated in the process.

The mammoth-pump-principle seems to be suitable. Two concentric pipes will be broughtdown. The warm water will be pumped down-wards through the inner tube, while water andreleased gas will stream upwards through theouter annulus (or vice versa). The flow of down-streaming water will be driven only by the difference of density between the fluids in theinner tube and the outer annulus. This densitydifference is equivalent to a pressure differencebetween the head of the inner tube and outerannulus, sufficient enough to pump the warmwater all the way down to the deposit.

Schultz H.J., Deerberg G., Schlüter S., Fahlenkamp H.

Fraunhofer-Institut für Umwelt-, Sicherheits- und Energietechnik UMSICHT, Essener Str. 99, 46047 Oberhausen,

heyko-juergen.schultz@umsicht.fhg.de

114

1 Outer tube, annulus (here: upcomer)2 Inner tube (here: downcomer)3 Hydrate reservoir, deposit4 Head, sea vehicle5 Sea surface6 Water, water column7 Sea floor8 sediment9 Fresh water supply10 Liquid overflow11 Product (gas) withdrawal12 Gas-partial flow, energy-generator-feed13 Energy-generator14 Hot burning gases,

heat transfer medium15 Offgas, waste heat usage16 Upcoming gas, product17 Upcoming solid (sediment, hydrate)18 Oil19 Separation apparatus for solid20 Solid withdrawal21 Separation apparatus for oil22 Oil withdrawal23 Cycle pump (start phase)24 Solid withdrawal pump25 Fresh water feed pump26 Oil withdrawal pump27 Liquid overflow valve28 Product (gas) withdrawal valve29 Gas-partial flow valve30 Heat exchanger

Figure 1:Application of the mammoth-pump-principleto controlled and safe upflow of oceanic gashydrates

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Reactor simulationThe transient implementation of the reactorsimulation is realised by a multi-area-cell-model. Figure 2 shows the 4 areas head, down,upcomer and bottom. Each area can be devided into N area-dependent, ideal mixed cells.A dynamic balancing for each cell of the reactorareas follows. In this context, the balanceequations of components (mass), energy andmomentum are obtained as a differential equation system and added by algebraic(approximation) equations. This results in a differential-algebraic-equation-(DAE-)systemthat can be solved by a numerical solver.

Thus, the simulation provides with time-depen-dant pressure-, concentration-, temperature-and velocity-profiles. Through dividing the fourreactor areas into cells, the profiles are present-able location-dependant, too.

Summary and outlookThe goal of this activity is to develop a simula-tion-program, that describes the destabilisa-tion and controlled extraction of oceanic gashydrates. Innovative removal technologies arenecessary for the safe, environmentally respon-sible examination of gas hydrate. The studywill deliver basic knowledge of a possible recovery technology for (instable) gas hydrates,which might be successfully realised in thenear future. With the help of the simulationcode, the evaluation of the proposed flow pro-cess will be possible. This evaluation consists oftwo main parts, technical feasibility and processsafety / risc evaluation. Parameter studies willgive further information about reactor-designadaptations. Hence, beside the technical feasi-bility and safety considerations, the objectiveof the study is the estimation of energetic effi-ciency of the gas hydrate winning process, i. e.the ratio of energy output (energy content ofhydrocarbon gas) and energy input (energyloss to surrounding and energy effort for ther-mal stimulation).The software code will be founded on amathematical model of the flow process. Thismodel incorporates the conservation balancesof mass, energy and momentum. The derivedequation system will be completed by data,assumptions, and models of the investigatedsingle phenomena (bubble flow, etc.). Multipleinteractions between relevant physical quanti-ties of the flow process, have to be consideredin this context. The simulation program will bea suitable tool for evaluating the describedtechnical approach.

Figure 2: Multi-area-cell-model for the gas hydrate extraction reactor

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Program for the simulation of gas hydrate equilibrium

Conceptual formulation and goal of this studyWithin the scope of a financially supportedresearch project (BMBF/Project 03G0550A),the task is to develop a computer-program todescribe the destabilisation and controlledextraction of oceanic gas hydrates. In order topredict the thermodynamic processes in a gashydrate deposit or an extraction apparatus,essential knowledge of hydrate formation/decomposition conditions is required. Theknowledge of the hydrate stability is importantfor the controlled destabilsation inside oceanicdeposits as well as for the rebuilding-preven-tion of gas hydrate in the extraction apparatus(plug-danger). Hence, a thermodynamic modulefor the calculation of hydrate equilibrium states (single- and multihydrate-former-systems) has been implemented in a first step.

Basics

IntroductionIn the last years, the gas hydrate topic is ofrising economical and ecological interest. Onthe one hand, the controlled use of gas hydrates as a ressource could guarantee theworldwide energy supply for a long time. Onthe other hand, the instability of this ressourcedepicts an exposure, i.e. an uncontrolled, climate affecting release of gas (hydrocarbons,mainly methane) from gas hydrates has to beavoided. Because of this, the controlled extrac-tion of gas hydrates is not only of economicalinterest but also of ecological and societal relevance in view of the preventive, climate-saving removal of instable hydrate fields.

Used ModelThe literature provides with results of differentcalculation programs for the estimation ofequilibrium conditions during hydrate formation[1], [2]. For this study it is necessary to im-plement a thermodynamic program, that canbe integrated in a superior program-environ-ment as a sub module.

The developed simulation tool is based uponthe fundamental considerations of van derWaals und Platteeuw [3]. Today, extended andimproved approaches exist, e.g. for multi-component-systems.

In a system of equilibrium state, the pressure,the temperature and the chemical potential ofall components in the participating phases areequal. The estimation of the thermodynamicequilibrium of the overall sytem is realised bythe determination of the chemical potentialsof water in the hydrate phase

and water in the liquid phase.

The potentials are referred to a common refe-rence state, i.e. the fictive modification β thatis thermodynamic unstable and describes acompletely empty hydrate lattice. Thus, theequilibrium condition can be written as:

Equation (1) results in:

Schultz H.J., Deerberg G., Schlüter S., Fahlenkamp H.

Fraunhofer-Institut für Umwelt-, Sicherheits- und Energietechnik UMSICHT, Essener Str. 99, 46047 Oberhausen,

heyko-juergen.schultz@umsicht.fhg.de

(1)

(2)

The potential differences in equation (1) arecalculated with further approaches. The development of the referring formulas andcorrelations can exemplarily be found in [1],[2], [3] and shall not be given here in detail. Inthe generated thermodynamic simulation program, equation (2) is solved iteratively bygiving a temperature value as the equilibriumtemperature and computating the associatedpressure value.

Simulation resultsThe used model provides the computation ofsingle- but also of multi-component gas hydrateequilibrium states with high accuracy. Themodel parameters (component dependentKihara-parameters) are mainly fitted to theextensive experimental data of Nixdorf [2].First, the respective parameters were fitted toone-component-systems. These parametersshowed good results for multi-component-systems, too. To demonstrate the computationresults in an example, the simulation for puremethane-hydrate is compared to the experi-mental data of Nixdorf in figure 1. The meandeviation for the shown range is 0,56%.During the equilibrium calculations, theLangmuir-constant is computed. In the imple-mented simulation program, the Langmuir-constant can be computed by three differentmethods, i.e.: - a potential-function (Kihara-interaction-

potential) [3], [2], [4], - an approximation function with constant-

data by Parrish and Prausnitz [4]- an approximation function with constant-

data by Munck, Skjold-Jörgensen andRasmussen [5].

According to this, a comparison between thethree methods is possible.

Summary and outlookWithin the scope of a research project for thedevelopment of a simulation-program, thatdescribes the destabilisation and controlledextraction of oceanic gas hydrates, a modular,thermodynamic program (“HYDRATPACK”)for the computation of one- and multi-compo-nent gas hydrate equilibrium systems has beenimplemented. Through this, component datacan be calculated by different equations ofstate and the Langmuir-constant, necessary forthe equilibrium considerations, can be computed by three different selectablemethods. The parameter fitting took placewith the aid of extensive experimental data ofNixdorf [2] and other researchers. The simulation tool delivers good results with thecomputation of gas hydrate equilibrium data.Further laboratory experiments concerninghydrate formation, inhibitor-influence etc. willlead the developed simulation tool HYDRAT-PACK to predict the formation conditions ingas pipelines. HYDRATPACK represents a contribution to the rising interest in the gashydrate topic. The poster will show furthercomparisons between experimental and simulation data, also for multi-component-

Figure 1: Comparison betweenexperiment and simulationfor methane-hydrate.

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systems. Additional to this, a comparison bet-ween different methods of calculating theLangmuir-constant will be given.

Literature[1] Sloan, E. D. Jr.: Clathrate Hydrates ofNatural Gases, Marcel Dekker Inc., New York1998

[2] Nixdorf, J.: Experimentelle und theoreti-sche Untersuchung der Hydratbildung vonErdgasen unter Betriebsbedingungen,Dissertation TH Karlsruhe, 1996

[3] Waals, J. H. van der; Platteeuw, J. C.:Clathrate Solutions, Adv. in Chemical Physics,In-terscience Publishers Inc., New York 1958

[4] Parrish, W. P.; Prausnitz, J. M.: Dissociationpressures of gas hydrates formed by gas mix-tures, Ind. Eng. Chem. Proc. Des. Develop. 11(1972) 1, S. 26-35

[5] Munck, J.; Skjold-Jörgensen, S.;Rasmussen, P.: Computations of theFormation of Gas Hydrates, Chem. Eng. Sci.43 (1988) 10, S. 2661-2672

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Gases and dissolved carbon compounds in thenorth-western Black Sea – concentrations andisotopic compositions (I+II)

For a comprehensive investigation of gas-hydrates and gas/fluid seeps of the north-western Black Sea the German research ProjectGHOSTDABS (Gas Hydrates: Occurrence,Stability, Transformation, Dynamics, andBiology in the Black Sea) in cooperation withRumanian, Russian and Ukrainian scientistswas founded. A research cruise using theRussian RV “Professor Logachev” was perfor-med in summer 2001. Deploying a rosettewater sampling system more than 100 watersamples were taken from the water column (0 – about 2.070 m water depths). Additionally,a unique set of sediment push cores as well asnear bottom water and gas samples weretaken with the German submersible “JAGO”between 65 and 325 m water depths.The secluded ecosystem of the Black Sea repre-sents an extraordinary research area. As aresult of the particular geo- and hydrologicalsettings of the Black Sea basin the ventilationof deeper water masses is restricted and a permanently anoxic zone has evolved duringthe last 7000 - 9000 years (Boudreau andLeblond, 1989). The downward flux of particulate organic mat-ter from the brackish surface waters leads toan accumulation of reduced inorganic andgaseous end products (e.g. NH4

+, HS –, CH4, H2

) and highly reduced organic compounds inthe deeper, more saline parts of the watercolumn (Karl and Knauer, 1991). Especially atthe north-western continental slope a greatnumber of distinct methane-rich seeps supply-ing enormous amounts of gas were observed(Egorov et al., 1998). Moreover, recent studies

in the central Black Sea and off the CrimeaPeninsula provide clear evidence for the occur-rence of mud volcanoes. For the first time gashydrates were illustrated at the studying area.To classify the sources of gases and carboncoumpounds in waters of the Ukrainian shelfarea numerous analyses of C1 – C4 hydro-carbons, dissolved inorganic carbon (DIC), dis-solved organic carbon (DOC) and stable carbon isotopic signatures (δ13C) of methanewere performed. Furthermore, contents ofnoble gases were determined for selectedwater samples.

In general extremely elevated amounts ofhydrocarbons were found in all anoxic sediment and water samples. Moreover, forconcentrations and isotopic compositions ofmethane interesting distribution patterns wereobserved in these environments.In a permanently anoxic non-seep related sedi-ment sample (320 m water depth, Fig. 1) CH4

concentrations increased with depth. At thesediment-water transition zone 21,5 [µmolCH4 L–1 sediment] were measured. Preliminaryresults of stable carbon isotopic measurementsrevealed continuous relative enrichments of13CH4 with decreasing sediment depth mostprobably due to AMO between 13 and 1 cm.δ13CH4 values of five near bottom water samples from different water depths typicallyranged from -51,5 to -57,2‰. In contrast, gasbubbles venting at same locations were relati-vely depleted in 13CH4 (- 58,5 up to -68,2‰).Concentrations of methane in anoxic watersamples decreased with decreasing water

Seifert R. (1), Blumenberg M. (1), Pape T. (1), Peterknecht K. (1), Thiel V. (1),

Schmale O. (1), Sültenfuß J. (2) , Rhein M. (2), Michaelis W. (1)

(1) Institute of Biogeochemistry and Marine Chemistry, University of Hamburg, Bundesstraße 55, 20146 Hamburg

(2) Institute of Environmental Physics/Oceanography, University of Bremen, Kufsteiner Str. 1, 28359 Bremen

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depth. Highest values (> 18 µmol L– 1) wereobserved at 1.700 m water depth and δ13 CH4

measurements indicate diverse microbial processes within the water column. Relativeenrichments in 13CH4 of different water depthswithin the anoxic zone are most probably dueto varying communities of methane oxidizingmicroorganisms.Results for dissolved noble gases revealedsupersaturation with respect to atmosphericequilibrium in deeper waters (Fig. 2). Thisenrichment of He and especially Ne might berelated to seep activity or gas hydrate forma-tion in the sediments.

Figure 1:Concentrations and carbon isotopic signature of methanein a permanently anoxic sediment (1-19 cm depth) on theUkrainian continental slope; (squares = concentrations,dots = δ13CH4).

Another objective of our field studies are theconcentration and isotopic compositions of spe-cific noble gases within the water column. XXXwater samples were analyzed for 3He, 4He and Ne

LiteratureBoudreau B. and Leblond P.H. (1989) A simpleevolutionary model for water and salt in theBlack Sea. Paleoceanography 4, 157-166.

Egorov V.N., Luth U., Luth C. and Gulin M.B.(1998) Gas seeps in the submarine DnieperCanyon, Black Sea: acoustic, video and trawldata. In: Methane gas seep explorations in theblack Sea (MEGASEEBS), Projekt Report (U.Luth, C. Luth and H. Thiel, eds.). Ber. ZentrumMeeres- u. Klimaforsch. Univ. Hamburg, ReiheE, 14, 11-21.

Karl D.M. and Knauer G.A. (1991) Microbialproduction and particvle flux in the upper 350m of the Black Sea. Deep-Sea Research 38(Suppl. 2) S921-S942.

Figure 2:Concentrations of noble gases in waters of the Ukrainiancontinental slope (water samples stations 65+66); (dots =δ3He, squares = δHe* (δHe, Ne corrected) and triangles =δNe).

Biomarkers and biogeochemical activity inmethane fed microbial mats of the Black Sea.

During the GHOSTDABS–cruise in July 2001,we could recover samples of massive microbialmats from the sea floor of the Black Sea usingthe German submarine ‘JAGO’ operated fromonboard the Russian R.V. ‘PROFESSOR LOGA-CHEV’. The sampling location south-west theCrimea peninsula was at 230m water depth,where huge microbial reefs thrive within theanoxic water body at active methane gasseeps. These reefs are composed by an assem-blage of individual structures emerging up to4m from the sea floor and composed of cm- todm-thick microbial mat which are internallystabilized by carbonate precipitates (Fig. 1).

The unique sample set of almost sediment freemassive microbial mats performing combinedanaerobic methane oxidation (AMO) and sulphate reduction (SR) allowed detailed biogeochemical studies not possible so far.

Lipid analyses of the macroscopically differenttypes of microbial mats (Fig. 1) – carbonateassociated brownish green mat (type I); massive pink mat (type II); gray to black coloredouter layer (type III) – revealed substantialdifferences between these three featuresregarding both their lipid composition and thecarbon isotope signature of individual compounds.

To obtain information on the biochemical processes, we incubated living microbial mat invitro under strictly anoxic conditions in a defined mineral medium and with 13C-enrichedmethane as the sole organic substrate (16 mMSO4

2-, 1.6 mM CH4). The microbial mats reducedsulphate rapidly and produced sulphide. More-over, the incorporation of methane derived 13Cinto the biomass could be observed for the bulkmat as well as for individual lipids.

Seifert R. (1), Nauhaus K. (2), Thiel V. (1), Blumenberg M. (1), Widdel F. (2), Michaelis W. (1)

(1) Institute of Biogeochemistry and Marine Chemistry , University of Hamburg, Bundesstrasse 55,

20146 Hamburg, Germany

(2) Max Planck Institute for Marine Microbiology, Celsiusstrasse, 28539 Bremen, Germany

Figure 1:Schematic cross section of a microbial formationdiscovered in the Black Sea.

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A novel benthic chamber for long-term in situ observation and experiments (LOTUS)

There is growing necessity to conduct long-term benthic observations and manipulativeexperiments under in situ conditions. Duringthe LOTUS project (www.gashydrate.de) within the German gas hydrate research initia-tive a novel benthic chamber to be integratedinto the GEOMAR Lander was designed to identify biogeochemical processes controllingthe composition and decomposition of surficialgas hydrates. During long-term in situ measu-rement series in gas hydrate containing sediments i. variability of benthic carbon turn-over, ii. variability of fluxes of oxygen, methaneand sulphide across the sediment water inter-face and iii. pathways of benthic carbon transfer will be determined.The sampling area of the new circular chamber(Figure 1) amounts 706.5 cm2 to obtain a largevolume of sediment for latter on-board analy-

sis, to account for mesoscale heterogeneity,and to provide a large area through which fluidand gas flow across the sediment water inter-face is possible.In order to record long-term variability of benthic turnover in semi-closed chambersystems it is of crucial importance to maintainthe oxygen supply at natural levels and toavoid severe oxygen depletion. Thus, to compensate for the total oxygen consumptionof the enclosed sediment community a gasexchange system (Figure 1) was designed. Thissystem facilitates oxygen transfer from a reservoir (approx. volume 35 l) containing saturated seawater into the benthic chamberacross silicone membranes.

Sommer, S. (1), Pfannkuche, O. (1), Linke, P. (1), Gust, G. (2), Gubsch S. (2)

(1) GEOMAR, Research Center for Marine Geosciences, 24148 Kiel, Germany

(2) Ocean Engineering 1, Technical University Hamburg-Harburg, 22305 Hamburg, Germany

Figure 1:Scheme of the benthicchamber and the gasexchange system.

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The design of this system is based on the coun-ter-current principle as realised in gills of e.g.fish, where oxygen enriched blood and oxygendepleted blood flows counter-currently along amembrane, which is permeable for oxygen.Oxygen transfer is mediated along a concen-tration gradient via diffusive transport. The gasexchange system tested possesses five mem-branes with a total gas exchange area of 392.7cm 2, however more membrane stacks can beintegrated into the system. The thickness ofthe membrane is 0,125 mm. Water flow withinthe chamber- and reservoir circuits is facilitatedby Seabird pumps. For tests two chambers were integrated into alander, a control chamber without a gasexchange system and a chamber fitted withsuch a system. The oxygen concentration inboth chambers and the reservoir was surveyedin water samples obtained by an automaticsyringe water sampler at defined time intervals(Figure 2). The silicone membrane of the gasexchange system is not only permeable foroxygen but also for methane and probably forother gases. Thus, this system in combinationwith the reservoir might be promising for thedetermination of diffusive fluxes of gases suchas CH4 and CO2 across the sediment water

interface.Advective and diffusive transport rates of solu-tes and micro-particulates across the sedimentwater interface are highly susceptible to varia-tions of the hydrodynamic regime. Thus, forthe accurate determination of material flux it isessential to either simulate the external flowregime inside the chamber or to set specificflow patterns for experimental purposes. Thisis accomplished by a mesocosm system. Theambient water flow is detected by currentmeters. Their signal is transformed into arespective rotating speed of the mesocosmdisc. This rotation in combination with an out-ward directed water flow through the centerof this disc generates a homogeneous flowfield above the sediment. An injector allows the introduction of particles(e.g. algae for food pulse experiments) or solu-tes into the chamber. This injector was alreadysuccessfully employed during food pulse stu-dies 4850 m deep at the Porcupine AbyssalPlain. Microsensors (O2 , H2S, pH) (Unisense, DK) andan oxygen optode (Aanderaa, NO) will monitorthe water body overlying the sediment. Withinthe next months a profiling system with micro-sensors inside the chamber will be developed.

Figure 2:Time course of the oxygen concentration in a chamber equipped with a gas exchangesystem in comparison with a control chambernot fitted with a gas exchange system and the reservoir during two tests.

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Physical Properties of Hydrate Bearing Sediments

IntroductionIn addition to seismic data, geophysical infor-mation from wireline logs can be valuable inthe detection and evaluation of gas hydrateintervals. In the focus of interest are the sonicvelocities and electric resistivities because theyare more strongly effected by the presence ofgas hydrate than other physical properties. Forexample downhole measurements of electricalresistivity and sonic velocity are used to derivegas hydrate saturations Sh based on Archie’sequation and Wyllie’s time average relation.These are semi-empirical equations which relate the measured physical value to volumetric properties as porosity and watersaturation SW. Not only the volumetric contentbut also the varying modes of the occurrenceof this substance, e.g. disseminated as porefilling material, nodular, layered, or massive,strongly influences the physical sediment properties. The influence of disseminated,nodular, and layered gas hydrate on electricand seismic properties is studied. In some casesthe results are significantly different from whatthe Archie equation with the standard cemen-tation and saturation exponent and the timeaverage relation would predict. However, up tonow little is known about the physical proper-ties of gas hydrate bearing sediments andmore data from bore hole investigations andlaboratory studies are urgently needed to get abetter understanding of gas hydrate reservoirs,to improve the existing interpretationmethods, and to develop new models.

Electrical PropertiesTo determine the amount of hydrate in thepore space from in situ measurements of electrical properties different author suggest

the use of Archie’s equation.

Sw: water saturation; φ: porosity; σw: conductivity of the pore filling brine; σ: conductivity of the rock; a,m,n: empirical parameters

For practical applications equation (1a) is oftenused with the resistivity index RI,

which is the ratio of rock conductivities whenthe rock is fully and partially saturated.Following this suggestion the fraction of thetotal pore space occupied by gas hydrates hasbeen estimated from resistivity measurementsin gas hydrate research wells (ODP Leg 164 siteand Mallik 2L-38). The empirical saturationexponent in both studies was chosen to n=1.9386. Our theoretical investigations onthe electrical properties of hydrate bearingloose sediments show that the Archie’s satura-tion exponent depends on the form of hydrateoccurrence, the properties of the host sediment, and that the saturation exponentdepends on saturation itself. If we take surfaceeffects into account, we found for pore spacehydrate that the saturation exponent dependsalso on grain size. The theoretical findingscould be proved by experiments on glass beadsamples (see. Figure 1).

Spangenberg E., Kulenkampff J.

GeoForschungsZentrum, Department of Petrophysics and Geothermics, Telegrafenberg, F222, 14473 Potsdam,

Germany, erik@gfz-potsdam.de, hannes@gfz-potsdam.de

(1a)

(1b)

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Elastic PropertiesTo study the influence of hydrate on the elasticproperties of loose sediments we used thesame geometrical models as for the modellingof the electrical properties. The results showsignificant differences to the time-average-relation and its derivates. The geometricalmodel we used for pore space hydrate is acubic sphere pack. Taking into account thatwater is the wetting phase, the hydrate formsapart from the grains in the pore space anddoes not act as a grain cement. For hydratesaturations greater 15% the model predictsthe formation of a hydrate skeleton within thepore space of the host sediment. The hydrateskeleton entraps the sand grains and producesa consolidated sediment. The transition fromthe unconsolidated to the consolidated stateof the sediment does not result in a clear change in the dependence of seismic wavevelocity on hydrate saturation . To prove thetheoretically predicted transition from theunconsolidated state to the consolidated athydrate saturations greater 15% we carriedout an experiment with loose sand, water, anddifferent THF-hydrate saturations. The experi-ment showed the transition in the predictedhydrate saturation range (see Figure 2).

Figure 1:Saturation exponent n as a function of watersaturation from experiments with glass beadsand modelling. The ratio r/L is the ratio of thegrain size with the bound water layer (r ) andwithout the bound water layer (L). Assuming a constant bound water layer this ratio characterizes the grain size.

Figure 2:Comparison between the time-average-relation, the time-average-relation adjusted for unconsolidated sediments, and oursphere pack model. The model predicted area of unconsolidatedconditions is shown together with a photograph of sand sampleswith different THF-hydrate saturation.

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Imaging of the internal structure of fluidupflow zones with detailed digital Parasoundechosounder surveys

Sites of venting fluids both with continuousand episodic supply often reveal complex surface and internal structures, which are diffi-cult to image and cause problems to transferresults from local sampling towards a structu-ral reconstruction and a quantification of (ave-rage) flux rates. Detailed acoustic and seismicsurveys would be required to retrieve this infor-mation, but also an appropriate environment,where fluid migration can be properly imagedfrom contrasts to unaffected areas. Hemi-pelagic sediments are most suitable, since typi-cally reflectors are coherent and of low lateralamplitude variation and structures are conti-nuous over distances much longer than thescale of fluid migration features.

During R/V Meteor Cruise M47/3 and R/VSonne Cruise SO 149 detailed studies werecarried out in the vicinity of potential fluidupflow zones in the Lower Congo Basin at 5°Sin 3000 m water depth and at the NorthernCascadia Margin in 1000 m water depth.Unexpected sampling of massive gas hydratesfrom the sea floor as well as of carbonate concretions, shell fragments and different liveforms indicated active fluid venting in typically hemipelagic realms.

The acoustic signature of such zones includescolumnar blanking, pockmark depressions atthe sea floor, association with small offsetfaults (< 1m). A dedicated survey with closelyspaced grid lines was carried out to image thespatial structure of the upflow zones with theParasound sediment echosounder (4 kHz),which data were digitally acquired with theParaDigMA System for further processing and

display. Due to the high data density, amplitudesand other acoustic properties could be investi-gated in a 3D volume and time slices as well asreflector surfaces were analyzed. Pronouncedlateral variations of reflection amplitudes within a complex pattern indicate potentialpathways for fluid/gas migration and occurren-ces of near-surface gas hydrate deposits,which may be used to trace detailed surfaceevidence from side scan sonar imaging downto depth and to support dedicated sampling.

Northern Cascadia MarginDuring R/V Sonne Cruise SO 149 (August2000) a small scale seismoacoustic survey wascarried out in the vicinity of recent gas hydratefindings on the sea floor. A dense grid of 25-50 m line spacing was measured with digitalsediment echosounder (Parasound/ ParaDigMA)and multi-channel seismics to reconstruct spatial patterns in potential fluid upflow zones.Digital Parasound data are presented in traditional profiles and as time slices averagingamplitudes over a depth range of 5 meters.Automatic algorithms were applied for de-spiking, navigation correction and smoothing.First arrival automatic picks were used to produce a bathymetric chart for comparisonwith Hydrosweep swath bathymetry.

An elongated low reflectivity zone in contrastto higher reflective layered sediments of hemipelagic turbiditic origin could be traced todepth. Gas hydrates were found near locationsof lower surface reflectivity indicating activemethane release. At depth, spatial reflectivitypatterns seem to indicate parallel bands ofreflecitivity, which may belong to a complex

Spieß V., Zühlsdorff L., von Lom-Keil H., Schwenk T.

Fachbereich Geowissenschaften, Universität Bremen, vspiess@uni-bremen.de

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fault system, lacking, however, a clear surfaceexpression.

Lower Congo BasinDuring R/V Meteor Cruise M47/3 sea floordepressions observed during previous GeoBresearch cruises to the area were investigatedin some detail to search for active venting andasscociated phenomena. In two sea floor samples(gravity cores) gas hydrates were found andbrought in large amounts up to the sea surface.

Bathymetric charting indicated several pock-marks with depressions on the order of 10-30m and diameters of 500-2000 meters. Most ofthese were visited during the cruise and indication of active venting had been found. Afine scale morphology of single pockmarkscould not be derived from swath sonar datadue to high variability of sounding data, whichmay be attributed to the extremely soft sediment of high water content and low surfa-ce reflectivity.

Therefore digital Parasound data had beenanalyzed to precisely determine water depththrough application of a first arrival pickalgorithm including despiking, editing andsmoothing steps as well as navigation proces-sing. The result is a digital Parasound bathy-metry. The morphology of the pockmark is clearly visible in greater detail revealing a depression deeper than 15 m and internalstructuring.

In the vicinity of Site GeoB 6520, where gashydrates had been collected from the sea floorand at ~4 m sub-bottom depth, high reflectionamplitudes were observed. AT locations withlow surface reflectivity, gas hydrates wereabsent, but indicators for fluid venting asmussles or carbonates were present. Hence,high amplitudes may be indicative for massivehydrates in high concentration, causing sufficient changes in acoustic impedance toincrease reflection coefficients. Accordingly,we assume that also at depth high amplitudesmay be related to gas hydrate accumulations,which in turn allows quantification of near-

surface hydrate from spatial Parasound surveys.

Results and ConclusionsDigital echosounder data are suitable to producethrough signal processing and automatic picking of first arrivals a high-resolution bathy-metry. Data quality and accuracy is superiourto swath sounder bathymetry derived fromcurrently installed systems on R/V Meteor andR/V Sonne, since only sea floor reflections areused lacking energy scattered over a longertime periods.- Digital echosounder were used to generate

a spatial image of fluid upflow zones inclu-ding detailed variations in surface topogra-phy and reflectivity as well as internal ampli-tude distributions and identification of faultsand columnar blanking zones.

- Amplitude maps in time slices allow to traceupflow zones, indicated by low amplitudesand absence of layering and related to com-plex structural patterns.

- At the Northern Cascadia Margin lateralamplitude variations seem to be controlledby structural disturbances (absence of laye-ring) rather than impregnation by hydrates.Columnar zones widen with depth and fol-low a planar surface

- In the Lower Congo Basin high reflectivityzones were identified both in the vicinityof gas hydrate findings at the sea floor aswell as near the assumed gas/fluidupflow, which indicates the presence ofgas hydrates as the main cause for highreflection amplitudes. Due to the low wetbulk density, normal reflection coefficientsare very low, and high amplitudes there-fore may indicate the presence of ele-ments of anomalous physical properties,mainly of higher velocity. High amplitudesfound around a 'chimney' of low reflecti-vity may indicate the gas supply chimney,and hydrate growth zones at its rim.

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Formation Kinetics of Porous Gas Hydrates

Clathrate hydrates form when water moleculesget into contact with gas molecules at the highpressure- low temperature conditions of stability of the hydrate phase. The under-standing of the formation process is importantfor a number of cases in geology and chemicalengineering. Unfortunately, our present under-standing of the physico-chemical processescontrolling the formation and decompositionkinetics is rather poor. We present here resultsof in situ diffraction experiments focused onthe formation of CH4 and CO2 gas hydrates atvariable pressure and temperature. The ratesof transformation of spherical grains (Fig. 1a)of deuterated ice Ih to gas hydrate were mea-sured using neutron and X-ray time-resolvedpowder diffraction at the high-flux diffracto-meter D20 at ILL, Grenoble and the high-ener-gy synchrotron beamline BW5 at HASYLAB,Hamburg respectively. A number of reactionswere followed over a period of 10 to 20 h.Data were analysed in an automated wayusing the Rietveled refinement program GSAS.Quantitative information on the amount of theformed gas hydrate was obtained as a functionof time. A comparison of the results from thedifferent formation runs leads to the followingconclusions:

- All reactions showed an initial fast and non-linear development followed by a slowerlinear behaviour with time.

- The pressure dependence of the rate of ice-to-methane hydrate transformation wasfound to be different at T=272.15K and atlow temperature T=230K.

- A clear difference between carbon dioxideand methane in the gas-hydrate formationkinetics was established. The reaction ofCO2 was distinctly faster than for CH4 atsimilar excess of fugacity (f-f0)/f0 (f0 -‚fugaci-

ty at the decomposition pressure). A maxi-mum conversion of ice Ih to type I gashydrate of 22% and 56% was obtained forCH4 and CO2 respectively. It seems probablethat this observation is connected to thesmaller pores sizes observed in CO2 hydrates(Kuhs et al. 2000) but we have no detailedunderstanding of the molecular processesinvolved at present.

- CO2 hydrate forms a transient type II crystalstructure in coexistence with the usual typeI hydrate reaching a maximum of 5% oftotal volume after 5h of reaction. The initialgrowth is rapid and appears to be preferredover a type I hydrate. This may indicate thatit is somewhat easier to form the smallcages of a hydrate structure (which aremore numerous in a type II hydrate) inagreement with suggestions by Sloan andFleyfel (1991) and experimental evidenceobtained by Pietrass et al (1995). The subse-quent re-growth of the type II hydrate intothe thermodynamically more stable type Ihydrate appears to be a very slow process.

The data were further analysed using a pheno-menological mathematical model (Salamatin &Kuhs, 2002). It is based on the electron microscopic evidence for a submicron porousmicrostructure of gas hydrates as observed byKuhs et al. (2000). The model describes theprincipal stages and rate-limiting processesthat control the kinetics of the porous gashydrate crystal growth from ice powders. Itseparates three stages of which the first twocould be observed in our experiments. Themodel assumes an initial stage of hydrate filmspreading over the ice surface and a secondstage, limited by the clathration reaction at theice-hydrate interface (and not by the gas transport to the ice/hydrate interface via the

Staykova D.K. (1), Goreshnik E. (1), Salamatin A.N. (2), Kuhs W.F. (1)

(1) GZG Abt. Kristallographie, Georg-August-Universität Göttingen, 37077 Göttingen, Germany

(2) Dept. of Applied Mathematics, Kazan State University, Kazan 420008, Russia

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sub-micron pores). This later stage prevailsafter the ice grain coating. Our electron microscopic pictures from a forming methanehydrate (Fig.1b) show that after 5h the ice surface is not fully covered with porous hydrate. The model assumes that initially the hydrateformation from the ice powder is controlled bywS, the rate of the clathrate film spreadingover the ice surface directly exposed to theambient gas phase. The total degree of thetransformation a develops with time as givenin equation (1):

where t is the time. A, B are functions of icegrain and initial hydrate film parameters andcould be regarded as constants. The parameterwS can be determined from eq. (1) when it isapplied as a fitting function f(t) to the experi-mental data of the hydrate mole fraction(Fig.2a). The data treatment showed no appreciable difference in wS for the different kinetic runs;in all cases the obtained value is around 0.014min– 1. This could suggest that the pressure andtemperature conditions in the system do playonly a minor role in the coating process.The model assumes that after the end of theice grain coverage with a hydrate shell thedominating rate-limiting process is the reactionon the ice/hydrate interface. Equation (2) isvalid for this stage:

It can be used to obtain parameters A and Bfrom a linear fit (Fig. 2b) of each data plot (1-α)1/3 = f(t>400min) in the time region ofvalidity of (2). Our data analysis gave us an esti-mation of 5.8 kcal/mol for the activation ener-gy necessary for the clathrate formation reac-tion after the end of hydrate film covering pro-cess of the ice surface. As this second stage ofthe reaction is not well developed at lowertemperatures due to the time limitations of ourfirst runs, this number must be considered aspreliminary and indicative only. It is most likely

only a lower bound as the measurements athigher temperature may be affected by a par-tial ice recrystallisation during the ongoingclathration reaction with some fusing of adja-cent grains, a process for which we can findsome evidence in our electron microscopicobservations. A full version of the paper will bepresented at the ICGH-2002 meeting inYokohama (Staykova at al., 2002)

Figure 1:FE-SEM pictures of (a) the ice spheres used as startingmaterial and (b) an ice grain after a 5 h reaction withCH4 gas at 60 bar and –1 °C showing a partial coveragewith porous gas hydrate.

(1)

(2)

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ReferencesKuhs, W.F., Klapproth, A., Gotthardt, F.,Techmer, K. & Heinrichs, T. (2000). The forma-tion of meso- and macroporous gas hydrates.Geophysical Research Letters 27 (18), 2929-2932.

Pietrass, T., Gaede, H.C., Bifone, A., Pines A.,and Ripmeester, J.A. (1995). MonitoringXenon Clathrate Hydrate Formation on IceSurfaces with Optically Enhanced 129XeNMR. Journal of American Chemical Society,117, 7520-7525.

Salamatin, A. N. & Kuhs W.F. (2002).Formation of Porous Gas Hydrates.Proceedings of the 4th InternationalConference on Gas Hydrates, Yokohama,Japan.

Sloan, E.D. & Fleyfel, F. (1991). A molecularmechanism for gas hydrate nucleation fromice. American Institute of ChemicalEngineering Journal, 37, 1281-1292.

Staykova, D.K., Hansen, Th. , Salamatin, A. N.& Kuhs, W.F. (2002). Kinetic diffraction experi-ments on the formation of porous gas-hydra-tes. Proceedings of the 4th InternationalConference on Gas Hydrates, Yokohama,Japan.

Figure 2:Results from a fit of data (a) of the methanehydrate formation reaction at P = 60 bar, T = 268 K with equation (1) of ice coveragestage and linear fits (b) of the second stagedata obtained for a reaction of CH4 hydrate at P = 60 bar and temperatures 230 and 268 K.

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Experimental and theoretical concepts toquantify deep-sea environments in anAutoclaved Experimental Chamber (AEC)

The design of the autoclaved experimentalchamber (AEC) of the BMBF gas hydrate research project OMEGA SP5 has been completed and the system is under construc-tion. AEC is a mobile, compact experimentalsystem suitable for on- and offshore as well asship operations to investigate natural and artificial gas hydrate/sediment samples under awide range of chemical, thermodynamic,hydrodynamic and biological aspects. Coresare introduced decompression-free from atransfer chamber via an adapter/pressure lock.The essential elements of the AEC, being thepressure vessel (working pressure: up to 55 MPa,interior dimensions: Ø300x1400 mm, weight:1.5 to, volume: 99 l) and the pressure adap-ter/lock with all peripheral components areintegrated into a seaworthy, certified 20ft-con-tainer.

To couple the autoclave coring unit carryingdecompression-free sediment samples as partof the laboratory transfer chamber (LTC,OMEGA SP1 of TU Berlin) to the AEC necessi-tated special modifications to the laboratorycontainer such as integration of a crane and ahatch. Sediment cores (Ø100x700 mm) aretransferred from the LTC into the AEC withoutloss of the original in-situ pressure and tempe-rature conditions (within acceptable error mar-gins). LTC transfer chamber and AEC arecoupled via an adapter/lock-chamber whichremoves (under pressure) the seal at the bottom of the LTC and guides the sedimentcore through an opened port into the AEC.Upon completion of the transfer, the sedimentcore is exposed in the AEC to an adjustable,controlled deep-sea environment representing

the in-situ conditions or conditions selected bythe user as to pressure, temperature, chemical surrounding and boundary layerhydrodynamics.

In addition to optical surveillance via pressureproof spy glasses and TV, a wealth of investi-gations are performed using sensors and different sub-sampling devices mounted withinthe pressurized volume. The handling of thesediment core (rotation and axial movement)and of all other kinetic tasks in the interior iscarried out by mechanic, hydraulic and electricinterfaces to the outside. Pressurized waterand/or gas of defined conditions from a 40-lreservoir is used for establishing settings whichrepresent boundary layer flow with fluid movement through the core; a simulation ofdeep-sea sediments with and without gashydrates and venting fluids. By measurementof the associated pressure differences, the z-component of the resistance-tensor maythus be determined. An alternative use of thereservoir is to provide a controlled source-sinkfeed through system for the fluid. Core exposure is not only feasible for natural sediment samples under defined thermo-dynamic/hydrodynamic/biogeochemical conditions, but also for artificial hydrate-con-taining samples generated inside the AEC andsubsequently destabilized. Investigations ofdestabilization with such a ‘standardisedhydrate core' permit to determine quantitati-vely the influence of environmental parameterssuch as pressure, temperature, chemical constituents and hydrodynamics with highrepeatability and accuracy for subsequentexperiments with natural samples. Exposure of

Steffen H., Gust G.

Ocean Engineering 1, Technical University Hamburg-Harburg, 22305 Hamburg, Germany

132

the core (both surface and pore space) toalmost natural hydrodynamics is an importantand unique feature of the AEC concept. It isimplemented by a technology developed andpatented by the MT1/TUHH research group. Anumerical evaluation of the interfacial bottomstress for various operational conditions isunder way, together with comparisons withexisting experimental data and an alternativeanalytical assessment. This aspect is of particularimportance, since we postulate the followingworking hypothesis concerning the influenceof hydrodynamics on the destabilization ofnatural marine gas hydrates:

- The shear generated by the movement ofwater near the bed enlarges the effective surface with active methane diffusion and consequently increases the destabilizationrate.

- Stronger turbulent boundary-layer flows increase the vertical flux of methane and consequently the destabilization rate.

- Increasing bottom stress enhances thedestabilization rate through removal of microscopically sized, intact hydrate cagesegments.

These hypothesis will be verified or falsified inupcoming experiments in the AEC.

It is expected that from the experiments underpreparation for the AEC both answers andnew questions on the role of gas hydrates inthe geosystem will arise. The presentation provides selected aspects of final design solutions, a video of the ongoing container-AEC system integration, and numerical resultsof the hydrodynamics established in the AEC.

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NATLAB: Seismic Parameters and PhysicalProperties of Marine Sediments

IntroductionThe main objective of the NATLAB-project isfocussed on the assessment of shear waves inthe sea floor under in-situ conditions and thecorrelation of shear wave velocities with sediment properties. The dynamic shear modu-li are very sensitive parameters with respect toshear strength and the stiffness of sediments,so that they allow an easy access to sea floorstability and offshore engineering problems.The shear wave velocities are obtained usingdispersion analysis of Scholte waves, which arealso observable in the lower part of the watercolumn and thus assessable by a continuouslytowed streamer just above the sea floor. Thismethod promises a higher efficiency for theinvestigation of sea areas in comparison withocean-bottom-seismometers. Furthermore,seismic parameters such as seismic reflectivityof gas containing layers and seismic velocitiesare evaluated for comparison with physicalsediment properties investigated with geologi-cal and geochemical methods on core samples. Three cruises have been performed in 2001 onRV ”Poseidon” and RV ”Alkor” in the ArkonaBasin and Kiel Bay for the acquisition of thegeophysical and geological data.

Results from Sea Experiments

Sediment properties in the Arkona Basin

During the cruise no. 266 of RV “POSEIDON”7 cores were recovered in the Kiel Bay area andin the Arkona Basin. The maximum core gainwas 11,2 m. Recent and subrecent greenmuddy sediments (recent to litorina-age), postglacial gray clay and silt and late glacialreddish silty clays were sampled in the ArkonaBasin. Sediments are characterized by different

gas contents indicated by zones with "seismicturbidity" or with clear structured seismic reflectors. The sedimentation boundariesdetected in the cores could well be correlatedwith the seismic reflectors.

Directly after the end of the cruise, selectedsections of the cores were investigated in thecore logger of the GEOMAR Institute forMarine Research with respect to the magneticsusceptibility, bulk density, and compressional(P-) wave velocity. The P-wave velocities showed reduced values of about 1150 m/s inthe recent near surface layers, whereas uncon-solidated water saturated sediments arecharacterized by values of 1450-1480 m/s. Thevelocity increases to 1400 m/s in the transitionzone from subrecent muddy sediments to subglacial clays which show values of up to1550 m/s (Fig. 1). The shear strength, measu-red with a mechanical probe, increases withdepth from 0,4 kg/cm2 up to about 1.5 kg/cm2.In the deeper sediment sections these valuesvary between 0,8 g/cm2 and 1,6 g/cm2 andamount up to 2,4 kg/cm2 in silt enriched layers.The bulk density increases in the same wayfrom 1,2 g/cm3 to 1,8 g/cm3.

Geochemical investigations have been performedon various cores sampled in the Arkona Basin.Sediment and pore water will be sedimentolo-gically and geochemically characterized. Besidegrain size measurements, density determina-tion, organic and inorganic carbon contentmeasurements the determination of the gascontent and composition in the sediments is amajor goal of the investigations. The meanconcentration of gas from pore water which isan important parameter for modelling the P-wave velocity structure, was about 150 ml/l.

Theilen Fr., Klein G., Thießen O., Schmidt M., Bohlen T.

Institut für Geowissenschaften der Christian-Albrechts-Universität zu Kiel

Figure1:Results of the analysis of core Po266-SL07 in the central Arkona Basin.Note the low P-velocity in the near surface due to high gas content.

Figure 2:a) Reflection seismic section from the south east rim of the Arkona Basin,Baltic Sea.The section shows the firstchannel at about 30m distance from the 0.1 l airgun, both at 5 m tow depth. Refracted first arrival occur due to the shallow water depth, dominantly nearby the location marked by the arrow.b) The p-f-domain spectra of a shot section near shot no. 9700 reveals thedispersive mode with phase slowness corresponding to 400-800 m/s.c) Forward modeling of a model derived from the reflection seismics and initial guesses for shear wave velocities.

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Nitrogen, methane and carbon dioxide werefound to be the main components. Hydrogensulfide was proven as well as trace componentin near surface layers. Moreover, gases (hydrocarbons) adsorbed on grain surfacesfrom grain size fraction <63_m has been measured. Gas saturation conditions are calculated for the various cores and sedimen-tological and geochemical data will be used forfurther seismic modelling.

Another important feature was observed insingle channel high frequency reflection seismic sections acquired with a boomer. Thespectra of this source covers mainly a frequencyrange of about 800 – 2600 Hz, which are normally observed on reflectors in gas freesediments. The reflections from gas-containinglayers are characterized by broad spectra covering a frequency range of up to 6500 Hz.The high frequencies are obviously caused bybackscattering from the gas bubbles in thesubsurface. It can be assumed that size of thebubbles and free gas content in the sedimentscorrelate with the seismic spectra. This effect isstrongly dependent on frequency. Frequencieslower than 500 Hz produce a strong reflectionwith inversed wavelet resulting in a negativereflection coefficient. This observation gaverise to the idea to perform modelling calcula-tions in order to get information on quantitati-ve relationships between the gas content andthe reflectivity patterns. This is probably an im-portant tool for the evaluation of BSR’s.

Scholte boundary wave experiments witha deep towed reflection seismic system inthe Arkona Basin

The geophysical investigations focus on theevaluation of the seismic data and test measurements on Scholte waves at selectedsites of the Arkona Basin. A reflection singlechannel seismic section of the area wheredispersive interface waves such as Scholtewaves have been recorded is shown in Fig. 2a.It is characterized by a weak sea floor reflection underlain by a series of strongerhorizons dipping slightly to the east. Especially

the strong reflector at 0.11 s TWT in the rangeof shot no. 9700 is remarcable, since it seemsto strongly affect the generation of the dispersive interface waves. This section yieldsthe basic subsurface structure for the derivation of a start model to calculate the theoretical dispersion spectra as shown in Fig.2c in the frequency range between 2 and 20 Hz.

The Scholte wave experiments have been performed on this profile using airguns withvolumes of 2,5 l and 1,2 l and a 200 m longstreamer, both towed about 8 - 10 m abovethe sea floor. The corresponding dispersionspectrum is shown in Fig. 2b. Note, that thedispersion mode is resolved within the frequency of 5 to 12 Hz, but resolution is poorotherwise. The inversion of the dispersion curves with respect to shear wave velocities asa function of depth by fitting the dispersioncurves requires the identification of the orderof the mode and is ambiguous in case ofstrong band limitation. Inversion methodswhich include information from the amplitudedistribution of the spectra may help to reducethe ambiguity. Therefore forward modellingunder consideration of the geological structureand the P-wave velocity structure derived fromreflection seismic sections as shown in Fig. 2awas used to produce an estimate of a velocitymodel such as shown in Fig. 2c.

In general, the experiments have shown, that itis possible to acquire dispersive interface waveswhich reveal information on the shear wavevelocity of the subsurface with a deep towedreflection seismic system. However, the frequency band showing clearly visible disper-sion curves is very limited, which implies thatthe use of a more sophisticated inversionmethod including information on the amplitudedistribution in the f-p spectra is favourable.This method has yet to be adapted for the prevailing marine environments.

The Scholte wave experiments show clearly,that the seismic sources should be operatednear the sea floor. Furthermore, experimentswith ocean bottom seismometers showed that

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Scholte waves are very slow in muddy sediments so that a special data acquisitiongeometry is required allowing close shot andreceiver distances.

Ackowledgements This project is funded by the BMBF under con-tract number 03G0564D. Thanks are also dueto the captains and crews of of RV “Poseidon”and RV “Alkor” for their excellent cooperation.

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Anaerobic oxidation of methane above gas hydrates

IntroductionAim of this study was to investigate rates ofanaerobic oxidation of methane (AOM) andsulphate reduction (SR) in methane-rich surface sediments at Hydrate Ridge (CascadianMargin, off Oregon). At this site methane isoxidized with sulphate by a consortium ofmethane-oxidizing archea and sulphate reducing bacteria (Boetius et al., 2000) via thefollowing net equation:

Sites with distinct microbial mats (Beggiatoa)and clams (Calyptogena) were sampled to inve-stigate the coupling of sulphate and methanecycles. The presence of Beggiatoa andCalyptogena indicates a high production ofhydrogen sulphide in the surface sediment asthese organisms use sulphide as an energysource. The production of sulphide at HydrateRidge is directly coupled with SR and thereforepossibly as well with AOM. Close-by siteswithout Beggiatoa or Calyptogena coveringwere sampled to obtain reference data.

Materials and MethodsSamples were obtained by a video-guided multicorer. Radioactive tracers of methane(14CH4) and sulphate (35SO4) were injected sepa-rately into subcores and incubated for 24 h atin situ temperature to measure AOM and SR.After incubation, the upper 10 cm of the sedi-ment cores were split into 1 cm intervals andfixed to stop the microbial activity. In the homelaboratory the ratio of 35S-sulphate to formed35S-hydrogen sulphide and of 14C-methane to

formed 14C-carbon dioxide respectively wasmeasured.

Results and DiscussionThe rates of AOM measured at Hydrate Ridgeare some of the highest ever found in coldmarine sediments (Fig.1). At the Calyptogena-site the rates reached up to 2.7 µmol/ccm/d insingle samples. Integrated over 0-10 cm sediment depth, the rates were highest at theCalyptogena-site (49.8 mmol/m2/d) followed bythe Beggiatoa-site (4.3 mmol/m2/d). Lowestrates (1.1 mmol/m2/d) were measured at theReference site. A close to 1:1 stoichiometry ofAOM and SR (as claimed in eqn 1) was foundat the Calyptogena-site. At the Beggiatoa-siteAOM was about one order of magnitude lowercompared to SR, indicating that sulphatereducers in the depth of AOM activity usedalso other electron donors than methane.AOM and SR followed the same pattern atboth high-sulphidic sites with subsurface peaksbetween 4 and 6 cm sediment depth. In correspondence, sulphate is rapidly depleted inthe depth of high SR activity. At the Referencesite methane oxidation and SR were not coupled. Methane oxidation was highest atthe sediment surface, indicating that the process might be aerobic. The SR profile ismore typical for organic rich sediments withincreasing activity beneath the oxic layer.Counts of consortium aggregates by fluore-scence microscopy revealed highest numbers(up to 1.5^108/ccm) at the sulphidic sites com-pared to rather low numbers (0.2^108/ccm) atthe Reference site. At the Beggiatoa-sitehighest aggregate abundance (1.3^108/ccm)

Treude T. (1), Boetius A. (1, 2), Knittel K. (1), Rickert D. (3)

(1) Max Planck Institute for Marine Microbiology, Celsiusstr. 1, 28359 Bremen, Germany,

Phone: ++49 421 2028 648, Fax: ++49 421 2028 690, Email: ttreude@mpi-bremen.de

(2) Alfred Wegener Institute for Polar and Marine Research, 27515 Bremerhaven, Germany

(3) GEOMAR Research Center for Marine Geosciences, 24148 Kiel, Germany

138

was found in the depth of the AOM and SRpeak.

ReferencesBoetius, A., Ravenschlag, K., Schubert, C.J.,Rickert, D., Widdel, F., Giesecke, A., Amann,R., Joergensen, B.B., Witte, U., Pfannkuche,O. (2000). A marine microbial consortiumapparently mediating anaerobic oxidation ofmethane. Nature 407, 623-626.

AcknowledgmentsThe fieldwork was done during Sonne expedi-tion SO 148-2, which was performed as partof the BMBF program TECFLUX. Laboratorystudies were performed within theGeotechnologien program MUMM.

Figure 1:AOM, SR and sulphate in three types of surface sediments at Hydrate Ridge.

139

INGGAS-Flux: New tools for energy and fluid-flux: pore pressure and thermal gradient probes

Two different tools are designed and testedwithin this INGGAS subproject:

1. a 6m long heat flow probe to expand measu-rement capabilities from deep sea environmentsto shallow water (continental margins) in ordermeasure reliable sediment temperature gra-dients in the presence of bottom water tempe-rature variations2. a pore pressure tool to measure in situ porepressures in sediments in order to quantify fluidflow. This second tool is split into two units: a)the data acquisition unit and b) an autonomous-ly operating data transmission buoy.

1 Heat flow probeThe new heat probe is capable to measure tem-perature gradients and in situ thermal conducti-vity in sediments to determine terrestrial heat

flow. The large penetration depth of 6m, twice asdeep as normally used instruments is necessary toget reliable results in water depth of less than2000m where varying bottom water tempera-tures create transient temperature disturban-ces in the subsurface. This is very often thecase for heat flow surveys over gas-hydratebearing sediments at continental margins. Themechanical design of the probe follows theviolin bow concept and is adapted in size andmaterial strength to the desired maximumpenetration depth. Numerical modeling of thedimensions of sensor string and strength mem-ber assisted in the final design. The data acqui-sition in the instrument is normally under real-time control from a deck unit on board theresearch vessel but can also be operated in acompletely autonomous way if no suitablecable is available on board.

Villinger H., Gennerich H.-H., Grevemeyer I., Kaul N.

Fachbereich Geowissenschaften, Universität Bremen, Postfach 330 440, 28213 Bremen, Germany

Data acquisition unit (in Data logger forheat probe at seafloor) • Signal conditioning of analogue temperature signal

• A/D conversion with 22 bit resolution• Data storage• Control of heat pulse for in situ thermal conductivity measurement• Data acquisition and storage of penetration monitoring sensors

(pressure, tilt, acceleration, altimeter)• Real-time communication with deck unit through coax deep sea cable• Temperature range of –2 to 70 °C• Temperature resolution of < 1mK from –2 ° to 12 °C• Battery and storage capacity allow continuous operation for 3 days• Operational up to 6 km water depth

Deck unit (on board PC for:research vessel) • Data capture and storage on hard disk

• Control of the instrument at the seafloor• Communication with the instrument at the seafloor through coax

deep sea cable• Real-time graphical display of data

140

The data acquisition system including the com-munication package is designed and built byan industry partner according to our specifica-tions. The complete mechanical system isshown in Figure 1. A first sea trial will takeplace during M54/2 off Costa Rica inAugust/September 2002.

2 Pore pressure toolThe goal is to detect vertical fluid flow withinseafloor sediments with rates as low as 1mm/a. This will be achieved by measuring porepressures in the sediments at various depthsfor a maximum period of two month with aminimal time resolution of 10 minutes tomonitor tidal and other low frequency effects.

We decided to employ one differential pressu-re transducer and three subsurface pressureports using a hydaulic multiplexer. Operationof the hydraulic multiplexer has been tested inthe laboratory and under deep ocean pressurecondition in a pressure chamber as well. Afterfree-falling to the seafloor the instrumentrecords pressures over a preset time windowand the data are transfered to the satellitecommunication unit. This unit will surface afterthe end of the measurement period and sendthe data to shore via an IRIDIUM satellite link.The complete system is designed as expenda-ble system to save additional ship time cost forrecovery of the data. A sketch of the systemdesign is shown in Figure 2.

Data acquisition unit Data logger for(pore pressure • Signal conditioning of analogue differential pressure signalmeasurement) • A/D conversion with 22 bit resolution

• Data storage• Data acquisition and storage of environmental

parameters (tilt, temperature)

• Data transmission to satellite communication unit• Battery and storage capacity allow continuous

operation for 2 months• Operational up to 6 km water depth

Satellite communication • Storage of pressure and environmental dataunit • Timing release

• Data compression• Transmission of complete data set through IRIDIUM

satellite link

The satellite communication system is desig-ned and built by an industry partner accordingto our specifications. The complete mechanicalsystem is shown in Figure 2. A first sea trial willtake place at the end of March 2002 in theBaltic Sea. A second test is scheduled forOctober 2002.

141

Figure 1:New heat probe with totallength of 8,1 m and aminimum total weight ofca. 900kg.

Figure 2:Sketch of the expendable differentialpore pressure probe. The data transmission unit is a self-containedsatellite data transmission link.

142

Fluid-geochemistry of active mud volcanoes in the Black Sea (OMEGA)

During cruise M52-1, sediment cores weretaken from the active Dvurechenskii mud volcano situated in the Sorokin Trough, BlackSea. Recovered sediments contained finelydispersed gas hydrates and fluids with anunusual composition. Thus, the dissolved chloride concentration increased to 850 mM, avalue twice as high as the average chloridecontent of Black Sea bottom waters. Thisstrong chloride enrichment could be caused bythe dissolution of evaporite rocks, by formation of gas hydrates, by phase separationat high temperatures (>350 °C) or might pointto the presence of ancient formation watersformed via evaporation of seawater.Surprisingly, the δ18O values of the recoveredbrines (-2‰ SMOW) were very close toambient bottom waters so that hydrate forma-tion and seawater evaporation could bediscounted as sole mechanisms of fluid forma-tion. In contrast, both evaporite dissolutionand phase separation at high-temperaturesmight enhance the chloride content of fluidswithout affecting the isotopic composition.

Currently, the fluids are further analyzed todecipher the possible formation mechanisms.Initial results indicate very high dissolved Ba, Band Li concentrations and low Mg values. Thischemical signature suggests very high temperatures in the source region and mighttherefore confirm the occurrence of phaseseparation at depth. If true, the studied mudvolcano would be associated with hydrother-mal processes which are usually driven by magmatic processes. Further in depth studiesare needed to confirm or discount this proposition.

Wallmann K., Bohrmann G., Drews M., Suess E.

GEOMAR Research Center for Marine Geosciences, Wischhofstrasse 1-3, 24148 Kiel, Germany

143

Mallik 2002: An In-situ Gas Hydrate Laboratory

From December 2001 to March 2002 fieldwork was conducted on a new gas hydrate research well program at the northea-stern edge of the Mackenzie Delta, NorthwestTerritories, Canada (Fig. 1 top). The Mallik research well program of 2001/2002 includesthe drilling of a 1200 m deep main productionresearch well (Mallik 3L-38) and, for the firsttime, two 1150 m deep scientific observationwells offset 40 m from the main well (Fig.) forgeophysical monitoring of the main well. Thescience and engineering research objectives forthe production research well focus on theassessment of the production properties of gashydrates, and the determination of the stabilityof continental gas hydrates.

After a long review process the drill site nearImperial Oil Mallik L-38, an industry explora-tion well drilled in 1972 (Bily and Dick 1974),was selected for the location of the gas hydrateresearch well program. This site located at theedge of the Mackenzie Delta, in Canada’sArctic was chosen as it offered favorable logistics and has the thickest known gas hydrateoccurrences in the region. Detailed geologic,geophysical and engineering data were availablefrom the original industry well and from aMallik 2L-38 (Fig.) a research well programconducted in 1998 (Dallimore et al. 1999).Well log interpretations and core samples fromthe 1998 research well revealed a strong lithological control on gas hydrate occurrencesat Mallik. For the most part, gas hydrate occur-red within coarse-grained sandy sedimentsthat were typically interbedded with non-gas-hydrate-bearing, or very low gas hydrate content, fine-grained silty sediments. On thebasis of the well log interpretations, more than110 m of well defined gas-hydrate-bearingsands and silty sands were found between 897and 1110 m (Collett et al. 1999). Quantitative

well-log-derived estimates suggest that in situgas hydrate concentrations are very high withgreater than 60% pore saturation throughoutmost gas hydrate layers, and in many casesmore than 80% pore saturation. Within thecored interval from 886 to 952 m, visible formsof gas hydrate occurred as pore fillings andcoatings on grain surfaces. In some sands andpebbly sands there were thin veins <1 mmthick and nodule-like gas hydrate up to 1 cm indiameter. In at least one interval of sandy con-glomerate the gas hydrate actually formed amatrix, which supported the pebble clasts.

A wide ranging research program is being conducted at Mallik 3L-38 with extensive research in geophysics, core studies and theapplication of several new technologies tomonitor in situ formation conditions. Full-scalefield experiments, which for the first time alsouse two additional observation wells, monito-red the physical behavior of the gas hydratedeposits and enclosing sediments to depressu-rization and thermal production stimulation. Asubstantially expanded science program forthis research well program has been enabledthrough the acceptance of a research proposalsubmitted by the authors of this article as anInternational Scientific Continental DrillingProgram (ICDP) project and it involves over 100researchers from more than 30 research institutes.

The project leaders are the Japan National OilCorporation (JNOC), the GeoForschungsZentrumPotsdam, Germany (GFZ), the GeologicalSurvey of Canada (GSC), the United StatesGeological Survey (USGS), the United StatesDepartment of the Energy (USDOE), the IndiaMinistry of Petroleum and the Natural Gas(MOPNG)1 and the Chevron-BP- Burlingtonjoint venture group1. On behalf of the project

Weber M.H. and the Mallik working group

GeoForschungsZentrum Potsdam, AB2, Telegrafenberg, 14473 Potsdam, Germany

144

leaders, Japex Canada Ltd. coordinates drillingoperations and the Geological Survey ofCanada coordinate scientific studies.

For further information see: http://www.gashydrate.com andhttp://icdp.gfz-potsdam.de.

1Partnership under negotiation

ReferencesBily, C., and Dick, J. W. L., 1974: Naturaloccurring gas hydrates in the MackenzieDelta, Northwest Territories; Bulletin ofCanadian Petroleum Geology, v. 22, no. 3, p.340-352.

Collett, T. S., Lewis, R., Dallimore, S. R., Lee,M. W., Mroz, T. H., and Uchida, T., 1999:Detailed evaluation of gas hydrate reservoirproperties using JAPEX/JNOC/GSC Mallik 2L-38 gas hydrate research well downhole well-log displays; in Scientific Resultsfrom JAPEX/JNOC/GSC Mallik 2L-38 GasHydrate Research Well, Mackenzie Delta,Northwest Territories, Canada, (ed.) S. R.Dallimore, T. Uchida, and T. S. Collett;Geological Survey of Canada, Bulletin 544.

Dallimore, S.R., Uchida, T., and Collett, T.S.,eds., 1999, Scientific Results fromJAPEX/JNOC/GSC Mallik 2L-38 Gas HydrateResearch Well, Mackenzie Delta, NorthwestTerritories, Canada: Geological Survey ofCanada Bulletin 544, 403 p.

Figure 1:Top - Location map showing site of the Mallik gas hydrate research well program, the winter ice roads andthe drill roads.Bottom - Detailed site layout showing surface conditionsand locations for main well (Mallik 3L-38) and the twoscientific observation wells.

145

Real-time mud gas monitoring at Mallik 4L-38 and 5L-38 wells

In order to investigate the composition and depthdistribution of gases occuring in the permafrostsedimentary setting of Mallik, we have analy-zed in real time the mud gas during drilling ofthe research wells Mallik 4L-38 and 5L-38 aswell as the gas liberated during a thermal production test. Gases dissolved in the drillmud were extracted using a gas separatorwhich was installed at the mud pipe outlet(Fig. 1). The liberated gas was led through aheated teflon tube (~ 25 m) into a laboratorytrailor. The gas was analysed for N2, O2, Ar, He,CO2, H2 and CH4 with a quadrupole mass spec-trometer, for 222Rn activity with an alpha-spec-trometer and for hydrocarbons (C1-C4) with agas chromatograph. Gas and drilled solidhydrate samples were taken routinely for furt-her detailed investigations in the GFZ laborato-ries. The depth distribution of gases was similar inboth wells. High methane concentrations inthe drill mud were found in shallow layers ofthe permafrost (106 m), at the bottom of the

permafrost (650 m), between permafrost andgas hydrate bearing zone (770 m, 840 m) and ingas hydrate layers (890 m - 1100 m). Most lay-ers can also be distinguished by their helium andradon concentrations and the C1/(C2+C3) ratio. A key question is whether the sedimentary section penetrated had the potential to gene-rate the observed gas occurrence in situ, orwhether the gases migrated to their presentlocation from deeper sources. Biogenic andthermogenic hydrocarbons differ in theirC1/(C2+C3) ratios about several orders ofmagnitude, which helps to clarify the origin ofthe hydrocarbons. In addition to the results of the mud gas moni-toring, isotopic investigations will give furtherindications about origin and genesis of thegas. In the future we plan to study the noblegas and stable isotopes composition of gassamples as well as the composition and ther-modynamic properties of gashydrate bearingsediments.

Wiersberg T., Zimmer M., Schicks J., Dahms E., Erzinger J., and the Mallik working group

GeoForschungsZentrum Potsdam, AB 4, Telegrafenberg, 14473 Potsdam, Germany

Figure 1:Experimental set-up

146

Multi-Frequency Seismic Data in the Vicinity ofa Gas Hydrate Site at the Northern CascadiaAccretionary Prism

During two research cruises of the German R/VSonne in 1996 and 2000 (Cruises SO 111 andSO 149 – ImageFlux), a dense grid of highresolution multi-channel seismic and hydro-acoustic lines was collected at the northernCascadia margin close to ODP Leg 146 Sites889 and 890. Detailed images of seafloorbathymetry provide information about sediment distribution, mass flow, and theeffects of regional tectonics (Fig. 1).Echosounder (Parasound) and 3D multi-channel seismic data are combined with supplementary single channel seismic anddeep-tow seismic data collected during twoCanadian cruises on R/V J. P. Tully (1997/1999).All data sets show a number of narrow, vertical blank zones and are compared nearcoring sites, where massive gas hydrates weresampled (Blank Zone 1, Fig. 2). If details likediffraction and high amplitude rims at theedges of the blank zones as well as the completeness of blanking are considered, theseismic signatures of both depositional structures and gas hydrates at or close to theseafloor are different for the different seismicsystems, depending on source type, frequencyrange, and lateral and vertical resolution.

Assuming that active fluid transport is requiredto form gas hydrate, which is often indicatedby the presence of a bottom-simulating reflector (BSR) in seismic data, mapping of BSRtopography and BSR distribution on the basisof SO 111 seismic data reveals informationabout the regional distribution of permeability.Since a clear BSR is present, diffuse fluid

migration is inferred for the pervasively fractured sediments of the accretionary wedge.In contrast, low-permeable bedded depositsappear to inhibit vertical flow and a BSR mayonly form below bedded deposits or in the vicinity of faults, where gas is locally providedat sufficient rates. An elevation of the BSR isinterpreted as a local disturbance of the thermal gradient, which is related to an increase in hydraulic conductivity within tectonically deformed sediments and a subsequent guided rise of warm fluids. Thus,the generally diffuse seepage of fluids withinthe study area is superimposed by events ofconfined fluid release.

Since massive gas hydrate was sampled atBlank Zone 1, fluid flow at this site also appears focused rather than diffuse, assumingthat the presence of gas hydrate is coupled tovertical fluid flow. If the seismic blanking within Blank Zone 1 is related to the presenceof gas hydrate or free gas, then there is no significant transition zone between the blankzone and hydrate or gas free sediments.However, although hydrate was sampled, it isstill difficult to conclude which kind of seismicsignatures are to be expected from massive gashydrate or sediments hosting gas hydrate. It isexpected that combining echosounder, swath-sounder, and seismic data sets for a joint analysis and interpretation will provide a uni-que opportunity to understand hydrate for-ming processes as well as the required deposi-tional and tectonic framework in greaterdetail.

Zühlsdorff L. (1), Spieß V. (1), Schwenk T. (1), Chapman N.R. (2), Riedel M. (2), Hyndman R.D. (2, 3)

(1) Dept. of Geosciences, University of Bremen, P. O. Box 330440, 28334 Bremen, Germany

(2) University of Victoria, School of Earth and Ocean Sciences, P. O. Box 3055, Victoria, BC, Canada

(3) Geological Survey of Canada, Pacific Geoscience Centre, P. O. Box 6000, Sidney, BC, Canada

147

Figure 1:3D image of ImageFluxswatch sounder data(Hydrosweep)

Figure 2:Comparison of ImageFlux data (Parasound,water gun, GI-Gun#2) and R/V J.P. Tully data(DTAGS, airgun). Massive gas hydrate wassampled at Blank Zone 1. a) stacked SCS airgun data, b) stacked MCS GI-Gun data, c) migrated MCS GI-Gun data, d) stackedDTAGS deep-tow data, e) stacked MCS watergun data, and f) Parasound narrow beam echosounding data.

148

Index

AAbegg, F. . . . . . . . . . . . . . . . . 8, 21, 23Aloisi, G.. . . . . . . . . . . . . . . . . . . 21, 33Amann, H. . . . . . . . . . . . . . . . . . . . . . 9Amann, R. . . . . . . . . . . . . . . 19, 67, 79Andreassen, K. . . . . . . . . . . . . . . . . . 29Artemov, Y.. . . . . . . . . . . . . . . . . 21, 83

BBauer, K. . . . . . . . . . . . . . . . . . . . . . . 11Baumert, J. . . . . . . . . . . . . . . . . . . . . 14Becker, H.J. . . . . . . . . . . . . . . . . . . . . 46Beer, D. de . . . . . . . . . . . . . . . . 19, 111Behain, D. . . . . . . . . . . . . . . . . . . . . . 17Bialas, J. . . . . . . . . . . . . . . . 21, 25, 107Blinova, V. . . . . . . . . . . . . . . . . . . . . 21Blumenberg, M. . . . . . . . . . . . 119, 121Bönnemann, C. . . . . . . . . . . . . . 17, 96Boetius, A.. . 19, 67, 72, 79, 98, 100, 137Bohlen, T. . . . . . . . . . . . . . . . . . . . . 133Bohrmann, G.. . . 8, 21, 23, 35, 65, 142Breitzke, M. . . . . . . . . . . . . . . . . . . . 25Broser, A. . . . . . . . . . . . . . . . . . . . . . 21Brückmann, W. . . . . . . . . . . . . 8, 28, 94Bünz, S. . . . . . . . . . . . . . . . . . . . . . . 29

CChapman, N.R. . . . . . . . . . . . . . . . . 146Conze, R. . . . . . . . . . . . . . . . . . . . . . 81

DDahms, E. . . . . . . . . . . . . . . . . . . . . 145Deerberg, G.. . . . . . . . . . . . . . 113, 116Dieckmann, V.. . . . . . . . . . . . . . . . . . 91Drews, M.. . . . . . . . . . . 21, 31, 33, 142

EEisenhauer, A. . . . . . . . . . . . . . . . . . . 35Elvert, M. . . . . . . . . . . . . . . . . . 19, 100Eppelin, A. . . . . . . . . . . . . . . . . . . . . 72Erbas, K. . . . . . . . . . . . . . . . . . . . . . . 53Erzinger, J. . . . . . . . . . . . . . . . . 36, 145

FFahlenkamp, H.. . . . . . . . . . . . 113, 116Feeser, V.. . . . . . . . . . . . . . . . . . . . . . 46Fischer, H. . . . . . . . . . . . . . . . . . . . . . 38Flüh, E. . . . . . . . . . . . . . . . . . . . . . . 107Fouchet, J.-P.. . . . . . . . . . . . . . . . . . . 21Freitag, J. . . . . . . . . . . . . . . . . . . . . . . 8

GGajewski, D. . . . . . . . . . . . . . . . . . . 107Gennerich, H.-H.. . . . . . . . . . . . 41, 139GHOSTDABS cruise . . . . . . . . . . . . . . 93Gieseke, A. . . . . . . . . . . . . . . . . . . . . 98Goreshnik, E. . . . . . . . . . . . 59, 74, 128Greinert, J. . . . . . . . . . . . 21, 44, 78, 83Grevemeyer, I.. . . . . . . . . . . . . . 41, 139Grupe, B. . . . . . . . . . . . . . . . . . . . . . 46Gubsch, S. . . . . . . . . . . . . . 49, 78, 122Gunkel, T. . . . . . . . . . . . . . . . . . . . . . 23Gust, G. . . . . . . . . 31, 49, 78, 122, 131Gutt, C. . . . . . . . . . . . . . . . . . . . . . . 14

HHaeckel, M. . . . . . . . . . . . . . . . . . . . 52Halbach, P. . . . . . . . . . . . . . . . . 56, 102Harris, J.M. . . . . . . . . . . . . . . . . . . . . 11Heidersdorf, F.. . . . . . . . . . . . . . . . . . 21Heinrich, T. . . . . . . . . . . . . . . . . . . . . 23

149

Index

Henninges, J. . . . . . . . . . . . . . . . . . . 53Hensen, C. . . . . . . . . . . . . . . . . . . . . 63Hoffmann, K. . . . . . . . . . . . . . . . . . . 46Hohnberg, H.-J. . . . . . . . . . . . . . . . . . 9Holscher B. . . . . . . . . . . . . . . . . . 31, 49Holzbecher, E. . . . . . . . . . . . . . . . . . 102Horsfield, B. . . . . . . . . . . . . . . . . . . . 91Hübner, A. . . . . . . . . . . . . . . . . . . . . 56Hübscher, C. . . . . . . . . . . . . . . . . . . 107Huenges, E. . . . . . . . . . . . . . . . . . . . 53Hyndman, R.D. . . . . . . . . . . . . . . . . 146

IItoh, H. . . . . . . . . . . . . . . . . . . . . 59, 74INGGAS working group . . . . . . 25, 107Ivanov, M. . . . . . . . . . . . . . . . . . . . . . 21

JJanssen, S. . . . . . . . . . . . . . . . . . . . . 14Jørgensen B.B. . . . . . . . . . . . . . . . . . 19

KKasten, S. . . . . . . . . . . . . . . . . . . . . . 63Kaul, N. . . . . . . . . . . . . . . . . . . 41, 139Keir, R. . . . . . . . . . . . . . . . . . . . . . . . 44Kipfstuhl, S. . . . . . . . . . . . . . . . . . . . . 8Klages, M. . . . . . . . . . . . . . . . . . . . . 79Klapproth, A. . . . . . . . . . . . . . . . 59, 74Klaucke, I.. . . . . . . . . . . . . . . . . . 21, 65Klein, G. . . . . . . . . . . . . . . . . . . . . . 133Knittel, K. . . . . . . . . 19, 67, 79, 98, 137Konerding, P. . . . . . . . . . . . . . . . . . . 85Krastel, S. . . . . . . . . . . . . . . . 21, 69, 83Kreiter, S. . . . . . . . . . . . . . . . . . . . . . 46

Krüger, M. . . . . . . . . . . . . . . . . . 19, 72Krysiak, F. . . . . . . . . . . . . . . . . . . . . . 81Kuhs, W.F. . . . . . . . . . . 23, 59, 74, 128Kukowski, N. . . . . . . . . . . . . . . . . . . 36Kulenkampff, J.. . . . . . . . . . . . . 76, 124

LLaframboise, R. . . . . . . . . . . . . . . . . . 81Leder, T. . . . . . . . . . . . . . . . . . . . . . . 21Lemke, A. . . . . . . . . . . . . . . . . . . 19, 67Liebetrau, V. . . . . . . . . . . . . . . . . . . . 35Linke, P. . . . . . . 23, 28, 35, 78, 94, 122Lom-Keil, H. von . . . . . . . . . . . 83, 126Lösekann, T. . . . . . . . . . . . . . . . . 19, 79Löwner, R.. . . . . . . . . . . . . . . . . . . . . 81Lüders, V. . . . . . . . . . . . . . . . . . 36, 109Lüdmann, T. . . . . . . . . . . . . . . . . . . . 85Luff, R. . . . . . . . . . . . . . . . . . . . . . . . 87

MMallik working group . . . . . . . 11, 53, 81, 91, 143, 145Mangelsdorf, K. . . . . . . . . . . . . . . . . 91Meyer, H. . . . . . . . . . . . . . . . . . . . . . 17Michaelis, W. . . . . . . . 93, 98, 119, 121Mienert, J. . . . . . . . . . . . . . . . . . . . . 29Mörz, T. . . . . . . . . . . . . . . . . . . . 28, 94Möller, P. . . . . . . . . . . . . . . . . . . 36, 109Müller, C. . . . . . . . . . . . . . . . . . . 17, 96Müller, V. . . . . . . . . . . . . . . . . . . . . . 49

150

Index

NNadalig, T.. . . . . . . . . . . . . . . . . . . . . 79Nauhaus, K. . . . . . . . . . 19, 72, 98, 121Naumann, R.. . . . . . . . . . . . . . . . 36, 76Neben, S. . . . . . . . . . . . . . . . . . . 17, 96Niemann, H. . . . . . . . . . . . . . . . 19, 100

O

PPape, T. . . . . . . . . . . . . . . . . . . . . . . 119Peckmann, J.. . . . . . . . . . . . . . . . . . 105Peterknecht, K. . . . . . . . . . . . . . . . . 119Pfannkuche, O. . . . . . . . . . . . . . 78, 122Polikarpov, I. . . . . . . . . . . . . . . . . . . . 21Poser, M. . . . . . . . . . . . . . . . 28, 78, 94Pratt, R.G. . . . . . . . . . . . . . . . . . . . . . 11Press, W. . . . . . . . . . . . . . . . . . . . . . . 14

Q

RReichel, Th. . . . . . . . . . . . . . . . . . . . 102Reimer, A. . . . . . . . . . . . . . . . . . . . . 105Reitner, J. . . . . . . . . . . . . . . . . . . . . 105Reston, T. . . . . . . . . . . . . . . . . . . . . 107Rhein, M. . . . . . . . . . . . . . . . . . . . . 119Richter, K.-U.. . . . . . . . . . . . . . . . . . . 38Rickert, D.. . . . . . . . . . . . . . 23, 52, 137Riedel, M. . . . . . . . . . . . . . . . . . . . . 146

SSaburova, M. . . . . . . . . . . . . . . . . . . 21Salamatin, A.N. . . . . . . . . . . . . . . . . 128

Sauter, E. . . . . . . . . . . . . . . . . . . . . . 79Savidis, S. . . . . . . . . . . . . . . . . . . . . . 46Schellig, F. . . . . . . . . . . . . . . . . . . . . . 21Schicks, J. . . . . . . . . . . . . . 36, 109, 145Schlüter, M. . . . . . . . . . . . . . . . . . . . 79Schlüter, S. . . . . . . . . . . . . . . . 113, 116Schmale, O. . . . . . . . . . . . . . . . 21, 119Schmaljohann, R. . . . . . . . . . . . . . . . 33Schmidt, J. . . . . . . . . . . . . . . . . . . . . 19Schmidt, M. . . . . . . . . . . . . . . . . . . 133Schmidt-Brauns, J. . . . . . . . . . . . . . 111Schneider, R. . . . . . . . . . . . . . . . . . . . 63Schrötter, J. . . . . . . . . . . . . . . . . . . . . 53Schultz, H.J. . . . . . . . . . . . . . . 113, 116Schupp, J. . . . . . . . . . . . . . . . . . . . . . 46Schwenk, T. . . . . . . . . . . . . . . 126, 146Seifert, R. . . . . . . . . . . . . . 93, 119, 121Shimizu, S. . . . . . . . . . . . . . . . . . . . . 11Sommer, S. . . . . . . . . . . . . . . . . 78, 122Spangenberg, E. . . . . . . . . . 36, 76, 124Spieß, V. . . 21, 44, 63, 69, 83, 126, 146Staykova, D. . . . . . . . . . . . . . . . . . . 128Steffen, H. . . . . . . . . . . . . . . . . . . . 131Suess, E. . . . . . . . . . . . . . . . 23, 52, 142Sültenfuß, J. . . . . . . . . . . . . . . . . . . 119

TTechmer, K. . . . . . . . . . . . . . . . . . . . . 23Teichert B.M.A. . . . . . . . . . . . . . . . . . 35Theilen, Fr. . . . . . . . . . . . . . . . 107, 133Thiel, V.. . . . . . . . . . . . . . . . . . 119, 121Thießen, O.. . . . . . . . . . . . . . . . . . . 133Treude, T. . . . . . . . . . . . 19, 72, 98, 137Tse, J. . . . . . . . . . . . . . . . . . . . . . . . . 14Türk, M. . . . . . . . . . . . . . . . . . . . 28, 94

151

Index

U

VViergutz, T. . . . . . . . . . . . . . . . . . . . . 49Villinger, H. . . . . . . . . . . . . 41, 107, 139Volkonskaya, A. . . . . . . . . . . . . . . . . 21

WWächter, J. . . . . . . . . . . . . . . . . . . . . 81Wallmann, K. . . 23, 31, 33, 52, 87, 142Weber, M.H. . . . . . . . . . . . . . . 11, 143Weinrebe, W. . . . . . . . . . . . . . . . 21, 65Widdel, F. . . . . . . . . . . . 19, 72, 98, 121Wiersberg, T.. . . . . . . . . . . . . . . . . . 145Wilkes, H. . . . . . . . . . . . . . . . . . . . . . 91Witte, U.. . . . . . . . . . . . . . . . . . . . . . 19Wong, H.K.. . . . . . . . . . . . . . . . . . . . 85

X

Y

ZZillmer, M.. . . . . . . . . . . . . . . . . . . . . 21Zimmer, M. . . . . . . . . . . . . . . . . . . . 145Zuehlsdorff, L.. . . . . . . . . . 69, 126, 146

Notes

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Notes

Notes

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Gas Hydrates in the GeosystemStatus SeminarGEOMAR Research Centre Kiel 6-7 May 2002

Programme & Abstracts

GEOTECHNOLOGIENScience Report

No. 1

Gas Hydrates in the Geosystem

ISSN: 1619-7399

Natural gas hydrates as a potential (i) energy resource, (ii) factor in global climatechange and (iii) trigger of submarine geohazard have received wide internationalattention in the past years.

In Germany, the national gas hydrate programme “Gas Hydrates in the Geosystem”has been initiated in 2000 as part of the new R&D programme GEOTECHNOLO-GIES, financed by the Federal Ministry for Education and Research (BMBF) and theGerman Research Council (DFG). The gas hydrate programme promotes a betterunderstanding of the nature of hydrates, hydrate-bearing sediments, and the inter-action between the global methane hydrate reservoir and the world’s oceans andatmosphere. Research projects covering a wide spectrum of science and technolo-gy, including geology, biogeochemistry, geophysics, physical chemistry andmechanical engineering. These are carried out in close collaboration betweenvarious national and international partners from academia and industry. Field stu-dies are underway at the Cascadia Margin off western North America, in the BlackSea, the Mackenzie Delta of the northwestern Canadian Arctic, and off-shoreCentral-America and Central-Africa.

This abstract volume contains the presentations given during four topical sessionsof the first status seminar “Gas Hydrates in the Geosystem” held at the GEOMARResearch Centre in Kiel, Germany. The abstracts reflect the multidisciplinary appro-ach of the programme and provides an excellent overview of where current gashydrate research in Germany stands.

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The GEOTECHNOLOGIES programme is financed by the Federal Ministry

for Education and Research (BMBF) and the German Research Council (DFG)