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DEPARTMENT PRIMARY INDUSTRIES AND ENERGY,AUSTRALIAN GEOLOGICAL SURVEY ORGANISATION

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CANNING BASIN PROJECTSTAGE 1, LENNARD SHELF:EXPLANATORY NOTES forSEISMIC and MAP FOLIOS

AGM RECORD 1993/1

Compiled by:MJ JacksonJM KennardM MoffatPE O'BrienMJ SextonPN SouthgateI Zeilinger

* R 9 3 0 0 0 1 *AUSTRALIAN GEOLOGICAL SURVEY ORGANISATION

DEPARTMENT OF PRIMARY INDUSTRIES AND ENERGY

Minister for Resources: The Hon. Alan GriffithsSecretary: Geoff Miller

AUSTRALIAN GEOLOGICAL SURVEY ORGANISATION(formerly BUREAU OF MINERAL RESOURCES, GEOLOGY AND GEOPHYSICS)

Exective Director: Roye Rutland

© Commonwealth of Australia, 1993

ISSN: 1039-0073ISBN: 0 642 18879 3

This work is copyright. Apart from any fair dealing for the purpose of study, research, criticism orreview, as permitted under the Copyright Act, no part may be reproduced by any process withoutwritten permission. Copyright is the responsibility of the Executive Director, Australian GeologicalSurvey Organisation. Inquiries should be directed to the Principal Information Officer, AustralianGeological Survey Organisation, GPO Box 378, Canberra City, ACT 2601, Australia.

This record accompanies and describes the Al-sized Seismic and Map Folios generated in Stage 1 ofthe Canning Basin Project. The Seismic Folio contains 1:50,000 scale interpretations and scanned un-interpreted copies of 84 seismic lines. The Map Folio contains 1:250 000 structure contour maps andisopach maps of major sequence boundaries and super sequences, and 1:100 000 isopach maps ofselected systems tracts of Devonian sequences in the Meda Embayment area. This record is not for saleseparately. Digital copy of seismic interpretations is also available in Petroseis format.

This information was gathered as part of the NATIONAL GEOSCIENCE MAPPING ACCORD, in ajoint project with the Geological Survey of Western Australia.

AUSTRALIAN GEOLOGICAL SURVEY ORGANISATION

••CONTENTS

• PageINTRODUCTION

• Project^ 1Folios

• Seismic Folio^ 1

•Map Folio

Acknowledgments^12

•Sequence Nomenclature 2Background and Regional Setting 2

• SEQUENCE STRATIGRAPHYGeneral^ 3

• Abbreviations^ 3Triassic to Early Permian^ 3

• Blina, Liveringa and Noonkanbah Sequences^ 3Poole Sequence^ 4

• Early Permian to Early Carboniferous

ft^Grant Sequences 4Anderson Sequences 4

Early Carboniferous to Middle Devonian• Overview^ 4

Regional Setting^ 5• Reef-rimmed Carbonate Platform^ 6

Mixed Siliciclastic-Carbonate Ramp^ 8• Givetian^ 9

Ordovician^ 9•

MAJOR FAULTS^ 9• Sixty Seven Mile Fault^ 9

May River Fault^ 10• Harvey Fault System^ 10

Transfer Faults^ 11• Mesozoic Wrench Structures^ 11

• STRUCTURE CONTOUR MAPSBase Givetian^ 11

• Base Famennian 1^ 11Base Toumaisian 1^ 12

• Base Anderson^ 12Base Grant^ 12

• Base Poole^ 12

• ISOPACH MAPS - STAGE 1 AREAGivetian-Frasnian^ 12

• Famennian-Early Tournaisian^ 13Laurel^ 13

• Anderson^ 13Grant^ 13

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STRUCTURAL HISTORY^ 15• REFERENCES^ 16

FIGURES^ 18•

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•AUSTRALIAN GEOLOGICAL SURVEY ORGANISATION

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ISOPACH MAPS - MEDA EMBAYMENT^ 13Systems Tract Relationships^ 13Petroleum Plays^ 14

CONTENTS OF SEISMIC FOLIO

PLATE 0^Locality Map: Seismic line and shot point detailsStructural Elements

PART 1- DETAILED INTERPRETATIONS, MEDA EVIBAYMENTSCALE 1:50 000, 1 S TWT = 10 cm

PLATE 1 H82-51 PLATE 5 H84-49H82-8.5 H84-50H82-9.5

PLATE 6 H84-51.6PLATE 2 H83-15.2 H84-8.5

H84-10.5 H84-AH84-11.2

PLATE 7 H84-BPLATE 3 H84-11.3 H85-6.6

H84-12.3 H85-7.5

PLATE 4 H84-13.2H84-15.3S

PART 2- STAGE 1 INTERPRETATIONSSCALE 1:50 000, is TWT = 5 CM

PLATE 8 BMR88-01 PLATE 18 ED87-592ED87-594

PLATE 9 BMR88-03 ED87-599

PLATE 10 ED81-09 PLATE 19 H87-19H80-09

PLATE 11 ED81-71ED81-73 PLATE 20 H80-57

H80-9.4PLATE 12 ED81-74 H80-P

ED81-76PLATE 21 H82-13.7

PLATE 13 ED81-77 H82-16.7ED81-79

PLATE 22 H82-15.9PLATE 14 ED81-80

ED81-81 PLATE 23 H82-17H82-17.5

PLATE 15 ED82-176 H82-18.7ED82-179

PLATE 24 H82-19.2PLATE 16 ED82-185 H82-19.4

ED83-262PLATE 25 H82-19EXT

PLATE 17 ED84-439 H82-20.7ED84-442 H82-20.7EXT

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PLATE 26 H82-3.7 PLATE 38 H84-15.3SH82-49 H84-19.6

PLATE 27 H82-5.2 PLATE 39 H84-19EH82-50E H84-21.5

PLATE 28 H82-51 PLATE 40 H84-22H84-48E

PLATE 29 H82-51.2PLATE 41 H84-49

PLATE 30 H82-51.6H82-52.2 PLATE 42 H84-50

PLATE 31 H82-52.6 PLATE 43 H84-51.6H82-53.7 H84-52.2

PLATE 32 H82-55.1 PLATE 44 H84-55.7H82-55.7 H84-57.3

PLATE 33 H82-8.5 PLATE 45 H84-58H82-9.5

PLATE 46 H84-8.5PLATE 34 H83-15.2 H84-A

H83-20PLATE 47 H84-B

PLATE 35 H84-10.5 H85-20.7H84-11.2 H85-55.9

PLATE 36 H84-11.3 PLATE 48 H85-6.6H84-12.3 H85-7.5

H86-13.4PLATE 37 H84-13.2 H86-55.8

H84-15.2H84-15.3N PLATE 49 W81-04

PLATE 50 W81-06W81-18

CONTENTS OF MAP FOLIO

PART 1^GENERAL MAPS

MAP 1 - Locations of seismic lines used in studyMAP 2 - Structural elements related to seismic lines

PART 2^STRUCTURE CONTOURS, STAGE 1 AREA, at 1:250 000 scale

MAP 3 - Base GivetianMAP 4 - Base Famennian 1 Sequence

MAP 5 - Base Tournaisian 1 SequenceMAP 6 - Base Anderson Sequence

MAP 7 - Base Grant SequenceMAP 8 - Base Poole Sequence

PART 3ÎSOPACH MAPS, STAGE 1 AREA, at 1:250 000 scale

MAP 9 - Givetian-FrasnianMAP 10 - Famennian-Early Toumaisian

MAP 11 - LaurelMAP 12 - Anderson

MAP 13 - Grant

PART 4ÎSOPACHS OF MEDA EMBAYMENT DETAILED STUDY AREAat 1:100 000 scale

MAP 14 - Frasnian 4, Lowstand Systems TractMAP 15 - Frasnian 4, Highstand Systems Tract

MAP 16 - Frasnian 4, Basin Floor FanMAP 17 - Famennian 2, Basin Floor Fan

MAP 18 - Fammenian 2, Lowstand Systems TractMAP 19 - Fammenian 2, Highstand Systems Tract

MAP 20 - Tournaisian 3, Lowstand Systems TractMAP 21 - Tournaisian 3, Highstand Systems Tract

PART 5ÊXAMPLES OF MAPS USED TO DEFINE PETROLEUM PLAYSin the MEDA EMBAYMENT at 1:180 000 (approx.) scale

MAP 22 - "FAN" Famennian 2 Basin Floor FanMAP 23 - "REEF Frasnian 4 Highstand Systems TractMAP 24 - "RAMP" Tournaisian 3 Highstand Systems Tract


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INTRODUCTION

PROJECTThe main aim of the Canning Basin project isto improve our understanding of the strati-graphic and structural evolution of the basin asa basis for more effective and efficient resourceexploration. The first stage of the projectinvolved studies on two contrasting scales; abasin-wide compilation of structuralinformation (not reported here), and a detailedstudy of the stratigraphic architecture andevolution of the outer portion of the centralpart of the Lennard Shelf, some of which ispresented here. The basic information gener-ated in the Lennard Shelf study has beencompiled into three folios: 1) a Well Foliocontaining sequence interpretations of the moreimportant wells in the area; 2) a Seismic Foliocontaining sequence interpretations of seismiclines; and 3) a Map Folio containing structurecontour and isopach maps. These explanatorynotes accompany the Seismic and Map Folios.More detailed discussions of the interpretationsof the Devonian-Carboniferous sequences arepresented in Jackson Sr others, (1992); KennardSE others, (1992) and Southgate St others, (1993).

FOLIOSSEISMIC FOLIOThe Seismic Folio contains sequence interpreta-tions (Plates 1 - 50) and scanned un-interpretedcopies (Plates 1a - 50a) of 84 seismic lines inthe Stage 1 study area (Plate 0). These seismiclines were chosen to provide ties to importantwells and to form an essentially regular gridthroughout the study area. This seismic grid isunderpinned by three surveys - AMAX Petro-leum Fitzroy Basin 1981 seismic survey; HomeEnergy Meda 1982 and 1984 seismic surveys.It also includes lines from 14 other surveysacquired during the period 1979 to 1987.Wherever possible migrated stack sections wereused in preference to final stacks, and the mostrecent or best quality lines were selected. Ourinterpretations were carried out on these full-sized lines and not the squeezed, scannedlines included in the folio.

The interpretations and scanned lines aredisplayed at a uniform horizontal scale of 1:50000. Two levels of interpretation are presentedin the folio:1) Sequence and systems tract boundaries of12 sequences within the Frasnian-Tournaisianreef and ramp complexes are interpreted for 18lines in the Meda-Yarrada area (Plates 1-7).

These interpretations are displayed at a verticalscale of 1 sec TWT = 10 cm.2) Major sequence boundaries and top base-ment are interpreted for each line. A total of 22sequence boundaries are interpreted, ranging inage from Ordovician to Triassic. These inter-pretations are displayed at a vertical scale of 1sec TWT = 5 cm (Plates 8-50).

In general only major sequence boundaries canbe resolved on vibroseis data acquired prior to1984 (source frequencies of 15-65 Hz). Howe-ver, sequence and systems tract boundaries canusually be resolved within the Devonian-Carboniferous succession on 1984 and morerecent vibroseis data (source frequencies of 12-90 Hz) in the Meda Embayment (Figure 2,Plates 1-7) and Kimberley Downs Embayment(Figure 3). Within the Meda Embayment,sequence and systems tract boundaries are tiedon all dip and strike lines in basinal settings;however, in platform settings, structural com-plexities and attenuation of seismic data be-neath platform carbonates prevents the inter-pretation of systems tracts on most strike lines.

Seismic interpretations were made on papersections supplied by either the permit holders(Petroleum Securites, Kufpec) or PetroleumInformation Corporation, Perth (under contractto the Western Australia Department of Mines).Seismic interpretations were integrated withwell interpretations, via synthetic seismogramsor time versus depth plots using availablevelocity data (see companion Well Folio).Interpretations were digitised into a Petroseisdata base and the interpretations were printedon a Versatec plotter.

MAP FOLIOThe Map Folio contains a selection of mapsgenerated from the Petroseis data base toillustrate aspects of the stratigraphy, structureand petroleum geology of the area. It compris-es 1:250 000 structure contour maps of sixmajor sequence boundaries, 1:250 000 isopachmaps of the intervals (super sequences) bound-ed by these major sequence boundaries, 1:100000 isopach maps of selected systems tracts ofDevonian sequences in the Meda Embayment,and combined structure contour-isopach mapsof three types of petroleum plays within theDevonian section. Contour maps were gener-ated by a CPS Radian 3 software package fromthe Petroseis seismic data base, incorporatingfaults, depositional limits, and zero edgeswhere necessary. The maps have also beenprinted on a Versatec plotter.


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ACKNOWLEDGMENTSThe Petroleum Securities Group, Bridge Oiland KLTFPEC are thanked for providing copiesof seismic lines and general information on thepetroleum geology of this part of the CanningBasin. Their co-operation and support isgreatly appreciated.

SEQUENCE NOMENCLATUREIn the Givetian-Tournaisian succession, eachsequence is identified by a number precededby an appropriate stage name (for example,Frasnian 4, Famennian 1 etc.). This chrono-stratigraphic nomenclature avoids use of exist-ing lithostratigraphic terms since many of theselithology-based units are commonly diachron-ous. Stage names are based on a review ofpalaeontological data from several wells in thestudy area (Jones & Young, in prep.) and theAustralian Phanerozoic Timescales producedby the Australian Bureau of Mineral Resources(now Australian Geological SurveyOrganisation; see list in References). This Stagebased sequence nomenclature has been compli-cated by new biostratigraphic data that indi-cates that some of our sequences pre or post-date the Stage in which they were firstassigned to. For example Famennian 3B and 4are now believed to be Tournaisian in age, andsince our original Frasnian 5 sequence probablyspans the Frasnian-Famennian Stage boundaryit has been renamed the Frasnian-FamennianSequence.

In the post Tournaisian succession, majorlithostratigraphic units were found to be essen-tially chronostratigraphic, and thus we haveused a sequence nomenclature based on exist-ing lithostratigraphic terms. For example, thePoole, Grant and Anderson Sequences areessentially similar to the Poole Sandstone,Grant Group and Anderson Formation; how-ever, they are not synonymous.

BACKGROUND AND REGIONALSETTINGThe vast Canning Basin in north-westernAustralia contains an unmetamorphosedPalaeozoic and Mesozoic section, possibly inexcess of 12000 m (Brown & others, 1984;Purcell, 1984; Drummond & others, 1991).Covering an onshore area of 430000 squarekilometres, it is one of Australia's largest basinswith promising, but as yet largely unfulfilled,petroleum potential. In a review of the pros-pectivity of the basin, Goldstein (1989) recog-nised at least sixteen distinct episodes of re-gional transgression, where potential reservoir

beds are sealed by shales, and noted that all ofthese are associated with oil and/or gas shows.

There have been several significant discoveriesof hydrocarbons within the basin and oil iscurrently produced from five small fields -Blina, Sundown, West Terrace, Lloyd andBoundary. Blina produces from carbonatereservoirs in the Upper Devonian-LowerCarboniferous, the other fields produce fromsiliciclastics of either the Grant Group orAnderson Formation. Proven reserves fromproducing fields total about 3.3 million barrelsof oil. Anzoil NL recently reported (FinancialReview, 24.11.92) the biggest gas flow yet fromthe basin (4.3 mill cu feet/day, half inch choke)in the Point Torment well, located only 25 kmfrom Derby.

The oldest known rocks in the Canning Basinare of earliest Ordovician (Tremodocian) age.Seismic lines in this area show theseOrdovician sediments preserved in a numberof tilted horst blocks, but little is known oftheir composition, setting or evolution. Theyare unconformably overlain by Middle toUpper Devonian rocks. During the Devonian,basin evolution was dominated by northeast-southwest extension which resulted in thedevelopment of the northwest-trending FitzroyTrough, one of the major structural provincesof the basin. This trough developed as a seriesof interconnected asymmetrical half-grabens,bounded either on their southwestern marginsby northeast-dipping listric faults or, in adja-cent compartments, by southwest-dippingnormal faults on their northeastern margins(Drummond & others, 1988, 1991).

The study area is situated along the hingednortheastern margin of one of these half-grabens. The basin sequence thickens gradual-ly across the Lennard Shelf into the FitzroyTrough, with the shelf margin delineated bythe May River and Harvey Fault systems.These faults have been depicted traditionally asmajor basin-bounding normal faults (Brown &others, 1984; Yeates & others, 1984), but bothrecent deep seismic information (Drummond &others, 1991) and our interpretations of shal-lower seismic data indicate this is not the case.In the study area, they are antithetic faultslinked, in part, to the major, northeast-dipping,listric Fenton Fault, which defines the south-western margin of the half-graben. This faultcrops out to the south-west of the study areaand represents a major basement detachmentsurface some 10-12 km deep below the studyarea. The May River, Sixty Seven Mile, Harvey


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and other antithetic faults along the margin ofthe Lennard Shelf form a system of en-echelongrowth structures that were active during theDevonian and were reactivated by trans-pression in the Mid Carboniferous and againduring the Late Triassic-Early Jurassic. Thesetwo transpressive events have generatedflower-type structures and large anticlinesthroughout the northern half of the basin.Many of these fault systems have providedmigration pathways for hydrocarbon accumula-tions on the Lennard Shelf.

Maps 1 and 2 show the geographic locations ofseismic lines and areas mapped in the folios,and their relationships to the main structuralfeatures.

SEQUENCE STRATIGRAPHYGENERALSequence stratigraphic concepts and models(Vail 1987; Posamentier and Vail 1988; Pos-amentier, Jervey, and Vail 1988; Sarg 1988; VanWagoner & others, 1990; Wornardt 1991) havebeen utilised to interpret well and seismicsections. By applying the technique to theinterpretation of well and seismic data we havebeen able to subdivide an apparently complexsedimentary succession into packages thatcorrespond to discrete depositional intervals.Sequence boundaries were identified on seis-mic sections by onlap and truncation surfaces,or abrupt changes in seismic facies. In wellsthey were identified by abrupt facies shifts onlithologic and electric logs or by gaps in thebiostratigraphic record; these boundaries werethen tied to seismic sections via syntheticseismographs or time depth plots derived fromvelocity data. For the more detailed interpreta-tion of the Frasnian-Tournaisian reef and rampcomplexes, component systems tracts wereidentified largely by - position in the sequence,toplap and downlap surfaces, cyclic repetitionof seismic facies, and ties to systems tractsidentified in wells by lithologic character,parasequence type and parasequence stackingpatterns.

From a petroleum exploration perspective, themajor advantage of sequence analysis is theability to predict the spatial and temporaldistribution and relationship between facies ofpetroleum significance (e.g. carbonaceousshales, porous sandstones, permeable carbon-ates).

ABBREVIATIONSThe following abbreviations of sequence strati-graphic terms have been used in the text andthe Seismic Folio: HST - Highstand SystemsTract; TST - Transgressive Systems Tract; SMST- Shelf Margin Systems Tract; LST - LowstandSystems Tract; PC - Prograding Complex; SF -Slope Fan; BFF - Basin Floor Fan; MFS - Maxi-mum Flooding Surface.

TRIASSIC to EARLY PERMIANSeismic reflectors above the Grant Sequencesare essentially parallel, so our sequence inter-pretation is largely based on well data (seecompanion Well Folio). Only major sequencesor sets of sequences have been interpreted onseismic lines for this part of the succession. Thenomenclature of these sequences is based onexisting stratigraphic nomenclature; for exam-ple, the Noonkanbah Sequence roughly corre-sponds to the Noonkanbah Formation. Weadopt this approach because uncertainties inbiostratigraphy make assignment of sequencesto a particular stage uncertain and becausethese sequences (except the Poole Sequence)are of a lower order (second-order cycles) thanthose in the Early Carboniferous to LateDevonian (third-order cycles). For instance, theNoonkanbah Sequence can be subdivided intothree 'sequences' on well criteria (see compan-ion Well Folio), but these are not evident onthe seismic in this area. This change insequence scale and geometry reflects the domi-nance of post-extensional, late thermal relax-ation subsidence through the later history ofthe basin. The generally parallel reflectors inthese sequences mean that sections displayonly rare evidence of onlap onto sequenceboundaries.

BLENA, LIVERINGA AND NOONKANBAHSEQUENCESThe seismic character of these sequences variesfrom survey to survey. They are best displayedon post-1983 lines from the deeper parts of theFitzroy Trough. Very little information isdisplayed on 1981 vintage lines. The BlinaSequence appears as a reflector-poor zone,probably because of its uniform lithology,whereas the underlying Liveringa Sequencedisplays abundant, relatively continuous reflec-tors, indicating lithological changes within theunit. The boundary between these two zonescorresponds closely with the Blina Sequenceboundary defined on well logs. The Noon-kanbah Sequence is reflection-poor comparedto the overlying Liveringa Sequence. Howeverit does feature two to three relatively contin-


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uous reflectors in the middle of the sequencethat possibly correspond to a second-ordermaximum flooding interval. The NoonkanbahSequence boundary, based on well ties, is at orclose to the top of a group of 2 to 4 relativelycontinuous reflectors that correspond to thePoole Sequence.

POOLE SEQUENCEThe Poole Sequence is a thin interval represent-ed by two to four reflectors depending on theresolution of the seismic survey. On shallowerparts of 1981 vintage lines, such as on the crestof anticlines, it is not resolved. On 1984 andlater lines it consists of several reflectors andlow angle onlap and truncation can be seen onits upper and lower sequence boundaries (e.g.,H84-11.2, ED84-439).

EARLY PERMIAN to EARLYCARBONIFEROUSGRANT SEQUENCESOn palynological grounds the Grant Group hasbeen subdivided into the Upper Grant andLower Grant successions (see companion WellFolio), but these successions cannot be differ-entiated on seismic data within the study area.This is caused by the preponderance of mas-sive sandstone in the lower part of the UpperGrant and the entire Lower Grant, so thatacoustic impedance contrasts are lacking.Therefore, in the Seismic and Well Folios theGrant Group consists of the Lower and/or theUpper Grant successions as defined in theaccompanying Well Folio. The top of the GrantGroup is defined by the base Poole Sequenceboundary, and on the Lennard Shelf its base iscommonly clearly defined by erosional trun-cation and onlap where it overlies Early Car-boniferous and Devonian sequences. Within theFitzroy Trough, however, the Grant Groupgenerally appears paraconformable with theAnderson Sequences.

Within the Grant Group, seismic lines displayboth reflection-rich and reflection-poor inter-vals. Well data suggests that most reflection-poor intervals are sandstone whereas reflection-rich intervals consist of interbedded sandstoneand mudstone. Truncation and onlap surfaceswithin the group indicate the presence oferosion surfaces with relief up to several hun-dred meters. The complex nesting of thesesurfaces made their mapping impractical in thisstudy. Velocity pull-ups can be seen beneathsome channels, probably because the Grantsandstones have a higher velocity than adjacentmud stones.

ANDERSON SEQUENCESIn this part of the basin the Anderson Forma-tion comprises marine to terrestrial clasticswith very minor carbonate. In the Stage 1 areathe Anderson sequence imaged on the seismicis the thin edge of a much thicker section inthe Fitzroy Trough. Because of this, and thegeneral absence of obvious sequence criteria onmost seismic lines a comprehensive sequencestratigraphic analysis was not carried out.

In several of the wells the Anderson Formationhas been sub-divided into three parts - YSequence, Anderson 2 and Anderson 1 (indescending stratigraphic order); see Well Folio.On seismic sections Anderson 1 and 2 cannotbe separated out. An attempt was made toseparate out the upper Y Sequence from therest of the Anderson on the seismic sections,but this was hampered by an absence of consis-tent seismic character and also a lack of se-quence criteria. On most of the lines where athicker Anderson sequence is preserved the Ysubdivision contains more obvious and con-tinuous reflectors; the underlying Anderson isa diffuse zone above the very bold reflectors ofthe Tournaisian.

EARLY CARBONIFEROUS to MIDDLEDEVONIANOVERVIEWIntegrated sequence analysis of seismic andwell data of the Givetian to Toumaisian sedi-mentary succession has recognised eighteenthird-order stratigraphic sequences in a majortransgressive-regressive (T-R) fades cycle (Fig.4). A Givetian phase of crustal extension initiat-ed the T-R cycle, and the cycle terminated inthe Tournaisian following a phase of slowthermal subsidence. The transgressive halfcycle comprises at least four third order se-quences; an initial Givetian-Frasnian sequencefollowed by three backstepping Frasnian se-quences. The regressive half-cycle comprisesfourteen third-order sequences in which overallbasinward advancement of the platform/shelfmargin is interrupted by three second-ordersealevel cycles which give rise to widespreadtransgressive marine shales within Famenniansequence 2A and Tournaisian sequences 1 and6. Tectonic uplift and erosion in the latestFrasnian resulted in a major basinward shift incoastal onlap in the initial stages of the regres-sive half cycle.

Sequence and systems tract geometries (Fig. 2),their stacking patterns and component faciesdefine two distinct styles of sedimentation:

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1) a Givetian to early Famennian, reef-rimmedplatform complex (Givetian-Frasnian sequence,Frasnian sequences 1-4 and Famennian sequen-ces 1-2B); and 2) a late Famennian to Town-aisian mixed carbonate and siliciclastic rampcomplex (Famennian sequences 3A-4 andToumaisian sequences 1-6). The Givetian-Frasnian sequence and Frasnian sequences 1-4correlate with the Pillara cycle, the Frasnian-Famennian sequence and Famennian sequences1, 2A and 2B correlate with the Nullara cycle ofPlayford (1980).

The reef complex demonstrates marked recip-rocal sedimentation; during lowstands terrigen-ous sediments by-passed the exposed platformto be deposited in the basin as basin floor fans,slope fans and prograding complexes. Duringtransgressions and highstands carbonate sedi-ments were deposited on the platform, allo-dapic carbonate particles were shed into proxi-mal marginal-slope settings and clastics weretrapped on the inner platform. Lowstandcarbonate production occurred locally in areasstarved of terrigenous dastic influx.

The recognition of relative sea level cycles inthese strata has led to a new model of reefdevelopment (Fig. 5) which provides insightsinto the third order cyclicity within the largerPillara and Nullara cycles recognised fromprevious outcrop studies. The previous outcropmodel of backstepping and advancing reefcomplexes emphasises transgressive and high-stand depositional systems, but fails to recog-nise phases of lowstand deposition.

The late Famennian-Tournaisian ramp complexcomprises nine basinward advancing sequences(Famennian 3A to Toumaisian 6). Each of thesesequences comprises a lowstand (?)clasticwedge (not intersected in any wells) and a thinand more laterally extensive, mixed carbonateand siliciclastic highstand deposit. Slope fansare restricted to Famennian sequences 3A, 3Band 4 and represent the gradual transition froma reef-rimmed platform to a distally-steepenedramp. Lowstand prograding complexes overliethe fans, and are the sole recognised lowstandcomponent of Toumaisian sequences 1-6.Toumaisian sequences 1 and 6 record twomajor trangsressive episodes that are character-ised by widespread marine shale deposition.

Systems tracts and facies within the reef andramp complexes are partitioned according totheir position on the T-R cycle; in the transgres-sive half cycle lowstand deposits are subduedand transgressive and highstand deposits

accentuated. In the regressive half cycle low-stand deposits are accentuated and provide afoundation for the overlying transgressive andhighstand deposits. The extent of basinwardhighstand progradation was limited by thebreak point of their underlying lowstanddeposits.

This sequence analysis provides a basis forpredicting the distribution of source, seal andreservoir facies within the reef and rampcomplex, and identifies new petroleum plays.Previous studies have been lithostratigraphic-based, focussing on carbonate depositionalfacies (Playford and Lowry 1966; Playford 1980,1982, 1984; Playford and others 1989; Druceand Radke 1979; Hall 1984), and their diag-enetic history (Kerans, and others 1986; Hurleyand Lohmann 1989; Wallace and others 1991).These lithostratigraphic units are markedlydiachronous and contrast with our new chrono-stratigraphic sequences. Subsurface explorationof the Lennard Shelf has been largely based onthe outcrop-derived model for reef growth, andanalogy to petroleum exploration in theDevonian Reef complexes of Alberta, WesternCanada (Playford 1982). Comparatively littleexploration activity has been focussed onbasinal deposits outboard of the reef-rimmedplatform.

Comprehensive analyses of the Devonian-Carbononiferous reef and ramp complexes inthe study area are given by Jackson and others(1992), Kennard and others (1992) and South-gate and others (in press).

REGIONAL SETTINGThe Middle Devonian to Early Carboniferousreef and ramp successions occur on the outermargin of the Lennard Shelf (Laurel DownsTerrace) and in the adjacent Fitzroy Trough.Transfer faults subdivide the trough, terraceand shelf into a series of compartments(Drummond and others 1988, 1991) which aremarked by offsets in the reef trend and abruptchanges in structural and stratigraphic geomet-ries and facies. Structural subdivisions in thearea (eg. Meda Embayment, Blackstone Highand Kimberley Downs Embayment) partlyresult from differential movement along trans-fer faults.

Most wells intersect dominantly platformsuccessions; basinal clastic facies are intersectedin Blina 1, Boronia, Janpam 1, Kennedia 1,Lukins 1, Mimosa 1 and Terrace 1. May River1 is the most inboard well, and Mimosa 1 andBoronia 1 are the most outboard wells studied.


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Age determinations are primarily based onconodont and microfloral data from cores andcuttings in the Blackstone 1, Langoora 1, MayRiver 1, Meda 1 and Mimosa 1 wells (Jonesand Young, in prep). Most of the wells drilledduring the 1980's have microfloral determina-tions from side wall cores.

REEF-RIMMED CARBONATE PLATFORMSequences in the reef-rimmed carbonate plat-form complex are grouped into two sets (Figs2, 5); the lower set displays successively back-stepping platform margins (Transgressive half-cycle comprising Givetian-Frasnian sequenceand Frasnian sequences 1-3), the upper setdisplays basinward advancing platform mar-gins (Regressive half-cycle comprising Frasniansequence 4, the Frasnian-Famennian sequenceand Famennian sequences 1-2B). A markedbasinward shift in coastal onlap occurs in theinitial portion of the regressive half-cycle, atthe base of the Frasnian-Famennian sequence.This shift reflects the onset of tectonic upliftand erosion in the Meda-Blackstone-Blina area.Within the regressive half-cycle, basinwardadvancement of the platform margin is tempor-ally interrupted by a second-order relativesealevel rise within Famennian sequences 2Aand 2B. This second-order cycle results in awidespread marine shale unit (the May RiverShale, Famennian 2A) and the suppression ofthe succeeding third-order sealevel fall; Fam-ennian sequence 2B is characterised by a shelfmargin systems tract, lacks lowstand depositsand is interpreted as overlying a type 2 se-quence boundary.

Thick lowstand deposits occur in the upper setof sequences where they display advancingplatform margins (Frasnian sequence 4, theFrasnian-Famennian sequence and Famenniansequences 1 and 2A). In the lower set of se-quences lowstand deposits are subdued. Plat-form carbonates dominate transgressive andhighstand deposits and basinal siliciclasticfacies dominate lowstand deposits. This tempo-ral and spatial separation of lithologies indi-cates reciprocal lowstand-highstand sedimenta-tion.

Lowstand Systems TractsLowstand deposits have been subdivided intothree seismically-defined depositional systems;1) basin floor fan, 2) slope fan and 3) pro-grading complex. A fourth depositionalsystem, shingled turbidites, is present at thetoes of some prograding complexes.

Basin floor fans form extensive sheet-like

deposits or aprons, tens of kilometres acrossand between 10-60 msec two way time thick(Maps 18,19). They onlap the sequenceboundary basinward of the platform marginand generally have upper boundaries definedby high-amplitude reflections; the amplitude ofthis reflection commonly diminishes near thepoint of onlap (eg, Famennian 2A, Line H84-A). This high amplitude reflection is interpret-ed to represent the contact between a sand-prone facies in the basin floor fan and a mud-silt prone fades in the overlying slope fan.Most basin floor fans lack internal reflections,but where present they are discontinuous andof low amplitude. Basin floor fans have beenintersected in the Frasnian 4 and Frasnian-Famennian sequences in Boronia 1 and Mimosa1 (see companion Well Folio).

Slope fan deposits form thick wedge-shapedunits above basin floor fans, and pinchout andonlap the sequence boundary at the slope ofthe previous platform margin. In contrast tothe clearly defined lower boundary describedabove, their upper surfaces vary from indistincttransitional intervals to high-amplitude reflec-tions. Discontinuous and hummocky, low-amplitude reflections, that locally display "gull-wing" patterns, characterise the internal partsof these deposits (eg, Line H84-19.6). Thesefeatures are interpreted to represent depositionin channel-levee complexes.In Slope fans havebeen intersected in Boronia 1, Luldns 1, Mimo-sa 1 (see companion Well Folio).

Prograding complexes usually comprise thethickest depositional system within the reef-rimmed complex. They form thick prograd-ational and aggradational lenses with locallywell-defined sigmoidal clinoforms that onlapthe sequence boundary at or near the previousplatform margin, and downlap basinward ontothe slope fans (eg, Fig. 3). Slightly mounded tohummocky low amplitude reflections locallydisrupt the sigmoidal dinoforms; these zonesmay represent slumps on the inclined surfaceof the prograding complex. The lower boun-daries of the prograding complex are locallyindistinct downlap surfaces that 'climb' basin-ward. Such surfaces are marked by the transi-tion from high-amplitude inclined reflections atthe toes of the sigmoidal clinoforms to discon-tinuous horizontal reflections of variable ampli-tude that extend basinward from these clino-forms (eg, Fig. 3). These relationships are inter-preted to represent shingled turbidites (asintersected in Lukins 1 for example; see com-panion Well Folio). In distal basinal settings,the base of the prograding complex may be


7

locally defined by a high-amplitude reflection.This relationship occurs as the progradingcomplex thins and may mark an interval ofsediment starvation and/or increased diag-enetic alteration.

Calcareous Lowstand Deposits: In theKimberley Downs Embayment significantlowstand carbonate production occurredaround topographic highs in areas of reducedclastic influx. In this area the Famennian 1sequence boundary is overlain by an interval ofdiscontinuous low amplitude reflections, thatdefine sigmoidal sediment wedges (Fig. 3).These rocks are intersected in Blina 1 andHarold 1 where they consist of limestone,sandy limestone, silty limestone and calcareoussiltstone (see companion Well Folio). In Fam-ennian sequence 2A lowstand carbonates areinterpreted to occur on the flanks of the plat-form within a seismically transparent zone 10-20 msecs two way time thick that mantles thesequence boundary. High amplitude clino-forms extend basinward from the transparentzone and are interpreted as tongues of carbon-ate-rich sediment; the distal toes of thesetongues are intersected in Lukins 1 where theycomprise silty and argillaceous bioclastic mud-stone and wackestone. Interfingering faciesrelationships between the lowstand siliciclasticand calcareous fades in Famennian sequences1 and 2A produces an unusual set of onlaprelationships (Fig. 3). Onlap of lowstandcarbonate units and the basin floor fan takesplace onto the sequence boundary. However,the remaining third order silicidastic lowstandunits onlap and bury these lowstand carbon-ates. For this relationship to occur carbonateproduction would have preceded siliciclasticdeposition and the interfingering relationshipprobably represents reciprocal sedimentation ata fourth order scale of cyclicity. We postulatethat encroaching lowstand siliciclastic depositsled to the demise of lowstand carbonate pro-duction.

Transgressive Systems TractAlthough transgressive and highstand depositsare the dominant systems tracts preserved inoutcrop, seismic data show that in the lateFrasnian and Famennian they are volumetrical-ly' minor compared to their related lowstanddeposits. On seismic sections transgressive andhighstand deposits are often difficult to distin-guish from each other. However, well logmotifs permit the identification of two types oftransgressive deposits (see companion WellFolio):1) Backstepping, and, 2) Keep-up.

Backstepping transgressive deposits: Thesedeposits are characterized by backsteppinggamma log motifs which define a series ofupward-thinning progradational parasequencescomposed of bioclastic carbonate, each para-sequence is terminated by a thin shaly carbon-ate interpreted to mark a flooding surface. Thebackstepping parasequence sets are overlain bya shale interval interpreted to represent acondensed section at the time of maximumflooding. On seismic sections it is not possibleto resolve backstepping parasequences. How-ever, an impedance contrast associated with thelow velocity shale and shaly limestone depositsof the condensed section and the encasinghigher velocity limestones results in a promi-nent high amplitude reflection that onlaps thesequence boundary in a platform position.This high amplitude reflection enables themaximum flooding surface to be mapped (eg,top May River shale unit, Famennian 2A;Laurel shales, Toumaisian 1, Toumaisian 6). Inbasinal positions the transgressive depositspinch out and the maximum flooding surfacemerges with the top of the progradingcomplex.

Keep-up transgressive deposits: In contrast tothe distinctive log patterns described above,backstepping log motifs and condensed sectiondeposits are subdued or lacking in keep-uptransgressive deposits. In consequence criteriafor delineating the boundary between trans-gressive and highstand deposits in keep-updepositional systems are commonly equivocal.However, in some cases parasequence cycles ofuniform thickness can be identified beneath asubdued condensed section; these cycles areinterpreted to represent reef growth in a keep-up transgressive depositional system. Para-sequences in the overlying highstand depositsare thinner than those in the transgressivedepositional system.

On seismic sections keep-up transgressivedeposits are 20-50 msecs TWT thick. Thesedeposits display similar seismic reflectioncharacteristics to the overlying highstanddeposits and only where a downlap surface isrecognisable at the base of the highstand is itpossible to bracket the underlying transgressivedeposits between this downlap surface and theunderlying sequence boundary or transgressivesurface.

Highstand Systems TractHighstand sediments form elongate, lenticularbodies that gradually thicken toward the plat-form margin, where they are 20-50 msec two


•••

8

way time thick, and then thin rapidly basin-ward to marginal-slope deposits, thus resultingin steep platform margins (eg, H84-10.5, seeMaps 15,17,21). Across the platform highstanddeposits display discontinuous parallel reflec-tions and at the platform margin sigmoid-oblique clinoforms. Where highstand depositsoverlie backstepping transgressive depositsthey downlap onto the high amplitudereflection marking the maximum floodingsurface. Where keep-up transgressive depositsunderlie highstand deposits it is often difficultto separate highstand clinoforms from trans-gressive clinoforms. In outer platform settingshighstand deposits have well-defined toplapsurfaces, in inner and middle platform settingsthe upper boundary of the highstand is adiscontinuous and irregular, high-amplitudereflection that may indicate karst. Highstanddeposits comprise inner-platform, back-reef,reef and fore-reef carbonate facies.

Shelf Margin Systems TractA shelf margin depositional system occurs atthe base of Famennian sequence 2B. The type2 sequence boundary is distinguished in wellsby a sharp change in the gamma log motif andan abrupt basinward shift of facies; on seismicit is marked by a distinctive onlap surface (Fig.3). The overlying shelf margin systems tract isis characterised on wireline logs by uniformlystacked parasequences, but is difficult to re-solve on seismic.

Givetian-Frasnian Sequence and FrasnianSequences 1-3 Seismic data did not permit the regional map-ping of depositional systems in the Givetian tomid Frasnian succession; interpretation of thissuccession was guided by the occurrence ofbackstepping platforms observed in outcrop(Playford and others, 1989). Frasnian sequences1-3 are recognised on six dip lines in the Meda-Yarrada area (shown as base Frasnian on H84-10.5, 11.3, 12.3, 13.2, H85-6.6, 7.5), and areintersected in Meda 1 and Yarrada 1. Thesesequences occur as a series of thin back-stepping units beneath and slightly basinwardof the prominent Frasnian 4 highstand buildup(Figs 2, 5). Each backstepping sequence isdefined by a set of low amplitude discontinu-ous clinoforms and a prominent onlap surface.In Meda 1 and Yarrada 1 these backsteppingsequences are intersected in a basinward posi-tion some 3-4 km outboard of the Frasnian 1platform margin. In both wells they comprisea 60-80 m thick succession of predominantlydolostone and dolomitic limestone, with threeprominent radioactive peaks (phosphate?) on

the gamma log, and some terrigenous sand andsilt in Yarrada 1; this succession is interpretedas a condensed, slope to basinal section ofFrasnian sequences 1-3.

Carbonates of the underlying Givetian-Frasniansequence are also intersected in Meda 1 andYarrada 1, but they cannot be mapped onavailable seismic data. Lowstand elastic sedi-ments of the Givetian-Frasnian sequence areinterpreted to occur in the Mimosa-Boronia-Kennedia area where they are truncated anddownlapped by the Frasnian-Famennian se-quence (see ED84-439, 442), and in the Minaarea where they are truncated and onlapped byFamennian sequence 1 (Fig. 3, H84-19.6, 22).

MIXED SILICICLASTIC-CARBONATE RAMPThe late Famennian-Tournaisian ramp complexcomprises nine basinward advancing sequences(Famennian sequence 3A to Tournaisian se-quence 6, Fig. 2). On seismic sections each ofthese sequences comprises a lowstand elasticwedge with sigmoidal internal reflections, anda thin and more laterally extensive, mixedcarbonate and siliciclastic highstand depositlacking internal reflections. Slope fans arerestricted to Famennian sequences 3A, 3B and4 (Fig. 2) and represent the gradual transitionfrom the reef-rimmed platform to the distally-steepened ramp (cf Read 1985). Lowstandprograding complexes overlie the fans, and arethe sole recognised lowstand component ofTournaisian sequences 1-6. Each highstanddeposit extends several kilometres across itsunderlying lowstand and thins basinward onceit reaches the break point of the underlyingprograding complex (eg Maps 20 & 21); high-stand progradation was apparently largelycontrolled by the break point of the underlyinglowstand deposits. Ramp sequences are welldeveloped on Lines H84-50 and H84-8.5.

In Tournaisian sequences 1 and 6 markedlandward shifts in coastal onlap are associatedwith relatively thick transgressive deposits. Onthe middle-inner ramp the sequence boundaryand associated maximum flooding surface atthe base of Tournaisian sequences 1 and 6 areimaged as "booming" reflections that form keymarker horizons. In well logs these majortransgressions are represented by prominentbackstepping gamma log patterns culminatingin the deposition of 10-20 m thick shale unitswhich mark the condensed sections. Oils in theSundown, West Terrace and Lloyd fields areprobably sourced from the shale at the base ofToumaisian sequence 1 (Goldstein 1989).

AUSTRALIAN GEOLOGICAL SURVEY ORGANISATION •

0•• Highstand deposits in Tournaisian sequences 1• and 2 consist of bioclastic grainstone, calcar-

eous sandstone, siltstone and shale. In inner• ramp positions of the Meda Embayment con-

tinued progradation of Tournaisian sequences3-5 results in either their absence, or theirthinning below seismic and well resolution.

• Lowstand deposits have not been intersectedby wells in the Stage 1 area. Further descrip-

• tions of ramp facies are given in the accompa-nying Well Folio.

GIVETIAN• Givetian sediments are present as complex

infilling of the half graben developed by mid• Devonian movement on the Sixty Seven Mile

Fault. These rocks appear on seismic lines as a• series of lenticular sequences that progressively

stack and step laterally to the northeast to-• wards the Sixty Seven Mile Fault. Each lens

pinches out by onlap to the northeast and by• downlap to the southwest, and their upper

surface is truncated by the base of the overly-* ing lens. The deeper lenses show a greater

tectonic tilt to the northeast because they have• rotated progressively with movement on the

fault. Lens geometry is also probably a function411^of the amount of rotation and movement

during the extensional event. These Givetian• lenses are intersected in the Mimosa, Boronia

and Kennedia wells where they compriseO poorly sorted very fine to coarse sandstone and

siltstone (undifferentiated Pillara/Napier• equivalents) that are interpreted as slope and

basin-floor fans. These landward-stackingGivetian fans are overlain by a series of basin-ward stacking slope and basin-floor fans (Give-

• tian-Frasnian, Frasnian 4 and Frasnian-Famen-nian Sequences) and the transition from land-ward-stacking to basinward-stacking fansindicates the termination of extensional

• movement of the Sixty Seven Mile Fault.

In this area the base of the Givetian successionis the top of a succession of relatively continu-ous, parallel events that can be traced back tothe top Poulten (?Eifelian) and Ordovician

• rocks in Blackstone-1 (see H82-51.2). Thissurface is best imaged on the 1980 and 1981

• vintage data.

• Givetian rocks probably comprise the north-eastward (landward) thinning wedge above

• Proterozoic basement in the Meda-May Riverarea (e.g., BMR88-01, H84-10.5, H85-7.5, H85-

• 6.6, H82-3.7), but the age of this succession hasnot been confirmed in the wells that intersect it

• (Meda 1, May River 1, Terrace 1). This wedgeis interpreted to thicken markedly across the

•

9

May River Fault into the Fitzroy Trough, andto continue thickening to the southwest to atleast 3.5 sec TWT.

ORDOVICIANThe top of the Ordovician package is delineat-ed by a set of parallel reflectors. This packageof parallel reflectors has clearly rotated as partof the hanging wall of the Sixty Seven MileFault without onlap onto either footwall orhangingwall, indicating that it predates faultmovement. The base of this package is poorlyimaged with reflectors fading into noise atbetween 1.5 to 2 sec TWT, and the upper partis intersected in Blackstone 1 where it compris-es interbedded shales and carbonates. A signifi-cant thickness of Ordovician strata is interpret-ed to have been eroded from the BlackstoneHigh (e.g., H82-15.9, H82-16.7, H82-51.2).Ordovician strata is absent on (but has prob-ably been eroded from) the Lennard Shelf inthe Meda-May River area, but probably occursbeneath interpreted Givetian strata at thenorthern margin of the Fitzroy Trough out-board of Meda 1 and Yarrada 1 (H82-51.2,BMR88-03, H84-10.5, H85-7.5). The originalextent of Ordovician strata in the Stage 1 areais poorly known.

MAJOR FAULTSMap 2 depicts the major structural elementsand faults in the Stage 1 area that have beenidentified and mapped. The terminologyfollows that adopted by Shaw & others (inprep). In this section, we briefly describe thestructural style of each major fault and itsprobable history.

SIXTY SEVEN MILE FAULTThe Sixty Seven Mile Fault delineates thenorthern margin of the Laurel Downs Terracewhich is a sub-division of the outer portion ofthe Lennard Shelf. It is a normal fault that dipsto the southwest at about 30 degrees, andshows major structural growth during the midDevonian (Givetian). Fault plane reflectors arerecognisable on some lines (eg. ED83-439) but"cross-overs" superimposed on probable sedi-mentary reflectors suggest that migration hasnot placed the fault plane its true place on thesections. Rotation of Ordovician and ?Eifelian(Poulton Formation) sediments, and the Giv-etian age of the half-graben infilling intersectedin Mimosa 1 (see well folio), indicates signifi-cant growth on the fault with concomitant


•

10

sedimentation from the Givetian. Rotation andnorthward stacking of Givetian fans indicatesthat displacement continued throughout theGivetian and probably extended into the Fras-nian. Displacement on the Sixty Seven MileFault is greatest in the southeastern part of thestudy area, decreasing to the northwest (Map3). In the northwest the fault terminatesagainst a probable vertical accommodationstructure - the Sundown Transfer Zone. Otheraccommodation structures along the SixtySeven Mile Fault consist of small step faults inthe footwall and antithetic faults in the hangingwall.

In the Blackstone-Blina-Mimosa area, the ro-tated Ordovician-Poulton section and Givetian-Frasnian infill of the Sixty Seven Mile half-graben were tilted, uplifted and eroded in thelate Frasnian (eg lines H82-51.2, H84-19.6, 22,ED84-439) to form the Blackstone High (Map3). Material eroded from the Blackstone Highwas then deposited as a wedge of late Frasnianclastics (Frasnian Sequence 4 and Frasnian-Famennian Sequence) in the Meda Embayment(H84-A, 10.5) and adjacent to the Sixty SevenMile Fault (ED84-439).

Renewed normal displacement on the SixtySeven Mile Fault in the early Famennian resul-ted in the formation of the Kimberley DownsEmbayment and submergence of the BlackstoneHigh. Enhanced carbonate production acrossthis high led to the development of the partial-ly detached Blina carbonate platform (Fam-ennian Sequence 1) which prograded south-ward into the Fitzroy Trough and, to a minorextent, northward into the Kimberley DownsEmbayment. Significant movement on theSixty Seven Mile Fault probably ceased in themid-late Famennian.

MAY RIVER FAULTThe May River Fault delineates the outermargin of the Lennard Shelf in the area northof the Sundown Transfer Zone. It is a south-west-dipping normal fault, but is significantlysteeper (-80 degrees) than the Sixty Seven MileFault from which it is offset 10 km to thesouthwest along the Sundown Transfer Zone.It if further offset by another northeast-trend-ing accommodation feature called the MedaTransfer Fault. The May River Fault appears tohave been initiated as a Givetian structureabove a deep basement arch imaged at ap-proximately 2-3 sec TWT (BMR88-01, H84-10.5,11.3). A thick ?Ordovician-Givetian section ispreserved on the downthrown block, but anyOrdovician section was stripped from the

upthrown block prior to the deposition of athin Givetian wedge across the outer portion ofthe Lennard Shelf.

The May River Fault was reactivated in theEarly to Mid Carboniferous, prior to depositionof the Grant Group. This transpressionalmovement resulted in local thickening andthinning of the Anderson Sequences, especiallythe Y unit, and the formation of small faultedanticlinal flower structures such as the MedaStructure (H84-10.5). Minor Mesozoic reactiv-ation of the May River Fault is indicated onmost seismic lines (eg BMR88-01, H85-6.6, 7.5,H82-3.7).

HARVEY FAULT SYSTEMAnother major northwest-trending fault systemcrosses the Stage 1 area about 20 km outboardof the faults described above. In previouspublications this fault system, or extensions ofit to the northwest and southeast, has beencalled the Beagle Bay Fault (eg Yeates andothers 1984), the Pinnacle Fault (eg Brown andothers, 1984; Playford and others, 1984), or theHarvey Fault (Purcell and Poll, 1984); we preferthe latter name. This fault system is sinistrallyoffset at the Sundown Transfer Zone. In thearea south of the Sundown Transfer Zone, itdelineates the southern margin of the LaurelDowns Terrace and thereby the Lennard Shelf.Here it forms a complex system of southwest-and northeast-dipping faults, delineating num-erous negative and positive flower structures,above a broad arch of Ordovician and base-ment strata (see BMR88-03, ED81-74, 76, 77, 80,81, H82-15.9; note base Givetian marks top ofOrdovician succession).

The Harvey Fault System appears to have beeninitiated above a structural high that wasonlapped and downlapped by Givetian andFrasnian strata, but the first evidence of faultdisplacement is abrupt changes in thickness ofFamennian Sequences 1 and 2 across andwithin local horsts and grabens (BMR88-03,W81-18, ED81-77, 80, 81, ED82-176). In theEarly to Mid Carboniferous it became a majorsouthwest-dipping normal fault such that theAnderson Sequences are preferentially pre-served beneath the Grant Group on the down-thrown side; the Anderson Sequences haveeither been largely stripped by base-Granterosion, or were originally much thinner, onthe northeast, upthrown, side of the fault. Thefault was reactivated during the Mesozoic(Fitzroy Movement) as a dextral transpress-sional fault (Rattigan, 1967) inverting the sedi-ments and producing the series of faulted


11

anticlines and synclines (positive and negativeflower structures) that have been the primarystructural targets for much of the oil explor-

• ation in this region. One such anticline formsthe trap responsible for the Sundown oilfield

• (H83-15.2); another is the structure tested byHakea 1 (ED83-262).

•On the northern side of the Sundown Transfer

• Zone the Harvey Fault System is less complex(in this compartment a major basement struc-

• ture occurs beneath the May River Fault ratherthan beneath the Harvey Fault System). Here,

O the Harvey Fault is a southeast-dipping normalfault, locally with two discrete anastomosing

• splays (see H84-11.2), which appears to havebeen initiated in the Early to Mid

• Carboniferous prior to deposition of the GrantGroup. Carboniferous displacement decreases

• progressively to the northwest (H82-9.5,BMR88-03, H84-8.5), and minor normal dis-

• placement subsequently occurred during theMesozoic (Fitzroy Movement).

TRANSFER FAULTS5^Transfer faults have been interpreted across theFitzroy Trough and Lennard Shelf by Begg

• (1987) and Drummond & others (1988, 1991).We have been able to identify one major or-

• thogonal structural zone in the Stage 1 area -the Sundown Transfer Zone - along which

• there is significant offset of extensional faults.This is a zone across which major Givetian

• movement on the Sixty Seven Mile Fault stepsapproximately 10 km to the southwest to the

• May River Fault on which Devonian displace-ment is more limited. Furthermore, the major

• Ordovician high beneath the Harvey FaultSystem appears to be displaced about 15 km to

• the northeast across this zone to the majorbasement high (now stripped of Ordovician

• strata) beneath the May River Fault.

O On transverse sections, the Sundown TransferZone is a region of poor reflector continuity inthe Devonian section with some doming andsagging of late Famennian and Tournaisian

• reflectors (eg. H82-51, 51.2, H84-A, 51.6, 52.2,H85-55.9, H86-55.8). Givetian and older succes-

• sions show marked offsets on either sides ofthe zone, and displacements generally decrease

• from Frasnian to Tournaisian sequences. TheGrant Group is essentially unaffected across the

• zone, indicating that structural movementceased by the mid Carboniferous.

•Other orthogonal transfer faults are: 1) a 4 km

• offset of the May River Fault along the MedaTransfer Fault, and 2) small (-1 km) steps in

•

the footwall of the Sixty Seven Mile Fault thatshow onlap of Devonian sequences and somedeformation of the Grant Group. TheBlackstone Transfer Fault (Shaw and others, inprep) is probably an extrapolation of one suchfootwall step (it is not shown on Map 2)

MESOZOIC WRENCH STRUCTURESThe transpressional event that caused react-ivation of the Harvey Fault System also formeda set of faulted anticlines in the southeast ofthe Stage 1 area outboard of the Harvey Fault.The Sisters Anticline is one such structure. In

seismic sections, these anticlines are positiveflower structures. They show no evidence ofPalaeozoic normal movement.

STRUCTURE CONTOURMAPS

BASE GIVETIAN (MAP 3)The base Givetian structure contour demon-strates subsidence and rotation of the LaurelDowns Terrace tilt block along the Sixty SevenMile Fault (fault plane cross-hachured). Rota-tion resulted in uplift of the outer margin ofthis tilt block to form the Blackstone Highwhich plunges to the southeast to the Blina andMimosa areas. This plunge results from differ-ential displacement on the Sixty Seven MileFault which increases to the southeast. To thesouth of the Blackstone High, the base Givetiansurface dips uniformly to the southwest and isprogressively onlapped by Givetian strata (egED81-77, BMR88-03).

In the area northwest of the Sundown TransferZone, the base Givetian surface dips to thesouthwest, and is downthrown about 200 msecon the southwest side of the May River Fault.

BASE FAMENNIAN 1 (MAP 4)The base Famennian 1 structure contour mapdepicts renewed subsidence of the LaurelDowns Terrace along the Sixty Seven MileFault to form the Kimberley Downs Embay-ment. The Blackstone High and its south-easterly extension in the Blina-Mimosa areaapproximates the southern margin of theEmbayment. This plateau-like high has aneroded upper surface (eg. seismic lines H82-51.2, H84-22, ED84-442) which plunges to thesoutheast. Detritus shed from this structuralhigh accumulated in lowstand deposits in theKimberley Downs and Meda Embayments. Tothe south of the Laurel Downs Terrace, the

-AUSTRALIAN GEOLOGICAL SURVEY ORGANISATION•

12

basal Famennian 1 surface dips to the south-west. The effects of subsequent wrench tecton-ism and the formation of anticlinal culmina-tions in the Sisters area is evident at this level,although it is not evident on the base GivetianMap. At the surface, Towner (1981) refers topart of this anticlinal culmination as the SistersStructure.

In the area northwest of the Sundown TransferZone the base Famennian 1 surface dips to thesouthwest and is downthrown at the MayRiver Fault against which the dips locallysteepen before resuming their more gentlesouthwestward trend.

BASE TOURNAISIAN 1 (MAP 5)The base Tournaisian 1 structure contour mapdepicts a southwesterly-dipping surface, trun-cated in its up-dip position by erosion at thebase of the Permian Grant Sequence. At thisstratigraphic level the Blackstone High issubdued, but still clearly evident. The Tourn-aisian 1 surface is locally steepened on thesouthern side of the May River Fault. TheSisters Structure also is clearly evident at thislevel.

BASE ANDERSON (MAP 6)The Anderson Sequence has been removed byerosion at the base of the Grant Group thro-ughout the northeastern part of the Stage 1area. The Blackstone High may still have beenactive at the start of deposition of theAnderson sequence, but due to the pre-Granterosion this cannot be confirmed. As with theprevious maps, the contours on the base of theAnderson Sequence indicate a southwesterly-dipping surface that has been upwarped into aseries of anticlinal culminations in the Sistersarea (Sisters Structure) outboard of the HarveyFault system. The influence of the SundownTransfer Zone on the Anderson surface is muchless obvious than at deeper stratigraphic levels.However, its continued influence at base And-erson level is suggested by the fact that thenorthwestern extent of the Sisters flower struct-ure is controlled by the location of the transferzone.

BASE GRANT (MAP 7)The most notable feature evident on the baseGrant structure contour map is a central terrace-like area, with low gradients, separating areasof southwesterly-dipping surfaces. This terraceis situated in the same position as theBlackstone High (Maps 3-6). As the strata inthis area were eroded prior to deposition of the

Grant Group, the presence of this terraceimplies rejuvenation of the Blackstone High,but we do not know if this is due to movementalong the same faults that were active earlier.The Sundown Transfer Zone has not beenshown on this map as clear evidence for itsaffect on the Grant and younger sequences isnot apparent on the seismic data; nor is itevident on the contour maps. However, thenorthwestern extent of the rejuvenatedBlackstone High coincides closely with theposition of the Sundown Transfer (cf Maps 6 &7), suggesting that this transfer fault may stillhave been active even this late in the evolutionof the area.

Although major channel features form the baseof the Grant Sequence on some seismic sec-tions, there are no obvious channel systemsvisible in plan view on this map.

BASE POOLE (MAP 8)The base Poole structure contour map showssimilar features to those described for theGrant. The only notable difference is thepresence of a northeast-trending ridge (A onMap 8) orthogonal to, but probably associatedwith, the Sisters structure; the origin andsignificance of this structure is not known.

ISOPACH MAPS -STAGE I AREA

GIVETIAN-FRASNIAN (MAP 9)The Givetian-Frasnian isopach encompassesGivetian clastic fans (Givetian Sequence), thePillara reef-building cycle (Givetian-FrasnianSequence and Frasnian Sequences 1-4), and theFrasnian-Famennian Sequence. It depicts sedi-ment accumulation triggered by the mid Giv-etian Fitzroy Extensional Movement, as well asthe late Frasnian uplift and erosion of the MayRiver, Blackstone and Sixty Seven Mile Highs.

On the Laurel Downs Terrace this successionforms a northwest-southeast trending wedgethat thickens northeastward into the SixtySeven Mile Fault and thins across the upliftedouter margin of the Laurel Downs Terracealong the Blackstone High. The succession alsothickens to the southeast along the axis of theSixty Seven Mile depocentre, and converselythins (and is locally absent due to erosion) onthe northwest nose of the Blackstone high.Within the Fitzroy Trough, the successionthickens uniformly to the southwest.


13

In the area northwest of the Sundown TransferZone, the Givetian-Frasnian succession thickensto the southwest across the Lennard Shelf,abruptly thickens into the Fitzroy Trough, andcontinues to thicken to the southwest withinthe trough.

FAIvIENNIAN-EARLY TOURNAISIAN(MAP 10)This map encompasses the Nullara reef-building cycle (Famennian Sequences 1, 2) andthe transitional reef to ramp early Tournaisiansediments (Famennian Sequences 3, 4). Thesuccession has a maximum thickness within theKimberley Downs Embayment and indicatesreactivation of the Sixty Seven Mile Fault withsubsidence and submergence of the LaurelDowns Terrace. This embayment was largelyfilled with mid Famennian lowstand clasticsdeposits (Famennian Sequences 1, 2) andsubsequently capped by transgressive andhighstand platform carbonates (Famennian 2B,3), thereby linking the isolated Blina platformto form a continuous platform across theLennard Shelf and Laurel Downs Terrace.

A secondary depocentre occurs within theembayment of the Fitzroy Trough on thenorthwest side of the Sundown Transfer Zone(i.e., the Meda Embayment), where lowstandFamennian clastic deposits are predominant (egMaps 17, 18). The Famennian-Early Tournais-ian succession thins across the Blackstone High,and thins onto the May River High.

LAUREL (MAP 11)Throughout most of the Stage 1 area Tourn-aisian Sequences 1-6 (the Laurel Formation)form a relatively thin sheet that is increasinglyeroded to the northeast by the base Grantsurface (cross-hachured area). However, thesuccession thickens markedly to the westacross the May River Fault and SundownTransfer Zone to form a major depocentrewithin the Meda Embayment. Thick lowstandprograding deposits accumulated within thisembayment (Map 20). Within this compartmentof the Fitzroy Trough, the Laurel Formationcontinues to thickens to the southwest, thusindicating extension and rapid subsidencealong the southern margin of the trough.

Possible local depocentres occur south of theHakea and Katy wells, but the seismic grid issparse in these areas.

ANDERSON (MAP 12)Due to the extensive erosion of the Anderson

sequence in the northeast half of the Stage 1area, little can be interpreted from the isopachmap. In the western half of the map area thesequence thickens gradually towards the south-west (ie into the Fitzroy Trough). In contrast,in the southeast of the area, the isopach con-tour trends are orthogonal to this, althoughdata control is limited. These northeast trendsare more like those in the overlying Grantsequence, but their origin is unknown.

GRANT (MAP 13)The Grant Group isopach map exhibits a re-gional thickening to the southwest, withoutobvious local structural control within theStage 1 area. This regional trend is interruptedin the Hakea area by 5 km-wide channel-likethickenings which trend northeast-southwest,orthogonal to the regional thickness trend.Here the Lower Grant Sequence is absent andthe Upper Grant succession erodes into theLaurel Formation (Toumaisian Sequences 1-6)or, outboard of the Harvey Fault System, theAnderson Sequences. These orthogonal thick-ness trends are interpreted as glacial erosionchannels at the base of the Upper Grant succes-sion.

ISOPACH MAPS -MEDA AREA

A selection of maps (Maps 14 - 21) from theMeda Embayment area, where we undertook amore detailed scale of sequence interpretation,has been included in the folio to illustrate theshape and distribution of some of the individ-ual systems tracts and their inter-relationships.The final three maps of this series (Maps 22, 23& 24) illustrate how this detailed systems tractsdata can be applied to petroleum exploration tomore accurately define the distribution andextent of potential source and reservoir units.

SYSTEMS TRACT RELATIONSHIPSMaps 14-15 and 18-19 have been generated toillustrate the geometries of, and spatial rel-ationships between, lowstand and highstanddeposits of a reef-rimmed carbonate platformsequence within the Nullara and Pillara reef-building cycles; Frasnian 4 and Famennian 2,respectively. For both sequences lowstanddeposits are more extensive and considerablythicker than their succeeding highstanddeposits, and the highstand depocentre approx-imately overlies the landward zero contour ofthe underlying lowstand, indicating markedreciprocal lowstand/highstand sedimentation.


14

Maps 15 and 19 show differences between thehighstands of the two sequences. Both show arelatively steep platform margin (or "reefedge") facing the basin to the southwest, butthe landward extent of the Frasnian highstandis more limited due to late Frasnian uplift anderosion ("Van Emmerick Movement"; Shaw andothers, in prep.). The platform margins parallelthe northwest-southeast trend of the May RiverFault, and then bend sharply to the southwestalong the trend of the Sundown Trasfer Zone(this later trend is obscured within the Frasnian4 sequence due to erosional stripping acrossthe outer portion of the Laurel Downs Terrace(ie, the Blackstone High) during the Van Emm-erick Movement). This structural control of theplatform margin has resulted in the develop-ment of the Meda Embayment which is delin-eated by the intersection of the northwesttrending May River Fault and the northeasttrending Sundown Transfer Zone. The Famen-nian 2 highstand depocentre and platformmargin are displaced 2-4 km to the southwestof their Frasnian 4 counterparts, thus indicatinga significant amount of platform margin advan-cement over a period of about 10 million years.

Maps 14 and 18 indicate that the Frasnian 4and Famennian 2 lowstand deposits are whollyrestricted to the Meda Embayrnent, and simil-arly indicate a 2-5 km basinward shift of theFamennian 2 lowstand deposits compared totheir Frasnian 4 counterpart. The basin floorfan (BFF) components of the lowstands areillustrated in Maps 16 and 17. Both BFFs arelocated in a distal position within their respect-ive lowstands. Their gross shape appears toreflect the constraints of the previous platformmargin (reef edge) to the north and a presum-ably fault-controlled reef margin related to theSundown Transfer Zone to the east. Jacksonand others (1992, Fig 11) suggest that the clasticmaterial comprising the fan originated from asource area to the east (the Blackstone High)and that it was transported down incisedfeeder channels. These channels were notmapped in this study, but have been mappedon better quality seismic data by geologists atPetroleum Securities (C. Knauer, pers. comm.).

The BFF isopachs suggest than the fans containnumerous lobate culminations, and gentlymounded upper surfaces of the fans are evi-dent on several seismic lines (eg, H84-A, 11.2,50). Although the two lowstands are of comp-arable thickness, the basin floor fan component(ie the more likely component to represent apotential reservoir) in the Frasnian 4 sequence(Map 16) is about twice as thick as that in the

Famennian 2 lowstand (Map 17). For bothsequences the lowstand and BFF deposits havecoincident thickness patterns; it would appear,therefore, that mapping of the larger systemstracts should offer a reasonable guide to thedistribution of the more likely BFF reservoirtargets.

As described in Jackson and others (1992), BFFsare seen as promising, but inadequately tested,petroleum plays; maps of these fans (Maps 16and 17) therefore represent useful models fordefining possible targets for drilling.

Maps 20 and 21 show lowstand and highstandisopachs of a distally-steepened ramp sequence(Tournaisian 3). The most obvious feature isthat this sequence was deposited to the south-west of the reef-related sequences describedabove, attesting to the gradual basinwardofflap of the succession through time. Thehighstand deposits are comparatively thin andsheet like and lack the steep margin character-istic of the older sequences. The basinwardextent of the highstand deposits (Map 21)appears to have been controlled by the breakpoint for the underlying lowstand deposits(Map 20).

The north-northeast trend of the lowstand iso-pachs contrasts with the more common east-northeast trends of the underlying reef sequen-ces described above and may reflect a gradualchange in the orientation of the basin due toaxial infill, or possibly it may indicate thecontrol of other orthogonal structures compar-able to the Sundown Transfer Zone.

PETROLEUM PLAYSThe final three maps in the folio are combinedisopach and structure contour maps from theMeda Embayment detailed study area (at areduced scale of approximately 1:180 000) thatdepict the three different play concepts des-cribed in detail in Jackson and other (1992).Map 22 depicts the basin floor fan at the baseof Famennian sequence 2, located immediatelywest of the Lloyd, Boundary and West TerraceOil Fields. This basin floor fan is about 4.5 kmacross and up to about 65 m thick. It has anumber of depositional lobes (mounded culm-inations) where we would expect sandstones ofthe BFF to be overlain and possibly sealed bysiltstone and shale at the toe of the overlyingslope fan. The fan is situated favourably alongthe postulated migration pathway from down-dip mature source rocks to the up-dip Lloyd,Boundary and West Terrace Oil Fields.


15

Map 23 shows the extent of the highstanddeposits of the Frasnian 4 sequence. In explo-ration terms, it shows the area within whichtransgressive and highstand pinnacle andbarrier reefs of this sequence could be expectedto occur. We feel that these reefs, which occurat the end of the Givetian-Frasniantransgressive half-cycle (Fig. 4), are prospective.We predict enhanced mouldic and vuggyporosity due to prolonged subaerial exposureand erosion associated with the late FrasnianVan Emmerick Movement, favourably locatedin an area up-dip from marine shales depositedoutboard of the underlying backsteppingFrasnian platforms. The reefs are overlain byinner platform facies of Famennian sequence 2which are likely to form a seal for this playtype. Although Frasnian reefs are difficult toidentify on the currently available data thesesorts of maps should help to identify areas forfuture high resolution seismic acquisition (eg,Kemp and Wilson, 1990) to assist in identifyingdrillable targets at this stratigraphic level.

Map 24 shows the third type of play conceptidentified - an offlapping carbonate ramp. Asfar as we know, none of the several rampsequences has been adequately tested by drill-ing. As illustrated in Jackson and others (1992,Fig. 7) part of the Toumaisian 3 highstand islikely to consist of inner shelf oolitic andbioclastic carbonates (potential reservoirs)located in a shoreward location from basinalshales (potential source), and encased intransgressive shales (potential seal). The Tour-naisian 3 highstand shown here is only oneexample of at least six similar ramp sequencesin this relatively small area.

STRUCTURAL HISTORYThe main structures in the study area are theseries of southwest-dipping normal (extension-al) faults described earlier. Some of thesemerge, at depth, with a major south-westdipping listric fault (Drummond and others,1991). In plan view, the extensional faultsterminate against or are orthogonally offset bythe Sundown Transfer Zone. A major base-ment high delineates the outer margin of theLennard Shelf (including the Laurel DownsTerrace), and this high, and thus the margin ofthe Lennard Shelf, is offset about 15 km to thenortheast on the northern side of the SundownTransfer Zone. Movement on these faults

appears to have proceeded in a basinwarddirection as evident from the following struc-tural history.1. Givetian extension along the Sixty SevenMile and May River Faults, and relative dis-placement across the Sundown Transfer Zone.On the upthrown blocks, a thin wedge ofGivetian clastic sediments onlap the SixtySeven Mile and May River Highs. Subsidenceand rotation of the Laurel Downs Terraceblock, and formation of a submerged protoBlackstone High.2. Late Frasnian regional uplift and erosion ofthe May River High, Sixty Seven Mile Highand outer margin of the Laurel Downs Terrace(emergence of the Blackstone High) - VanEmmerick Movement (Shaw and others, inprep.). These areas became a source of clasticand reworked carbonate detritus for thicklowstand deposits of Frasnian Sequence 4 andthe Frasnian-Famennian Sequence.3. Renewed early Famennian extension of theSixty Seven Mile Fault to form the KimberleyDowns Embayment and submergence of theBlackstone-Blina High to form the Blina car-bonate platform (Famennian Sequences 1 and2). Minor normal faulting was initiated on theHarvey Fault System at this time, and minormovement may have occurred on the MayRiver Fault.4. Early to Mid Carboniferous transpressionresulted in movement on the Harvey Fault,May River Fault and Sundown Transfer Zone.Local thickening of the Anderson Sequencesacross these faults indicate either syndepositionfaulting, or postdepositional faulting anderosion of the Anderson Sequences from theuplifted blocks at the base of the Grant Group.5. Mesozoic (Late Triassic to Early Jurassic)right lateral transpression along the HarveyFault System to form a series of faulted anti-cline.


16

REFERENCES

ARCHBOLD N.W. & DICKENS J.M., 1989 - AustralianPhanerozoic Timescales: 6. Permian. Biostratigraphic Chartand Explanatory Notes. Bureau Mineral Resources,Australia, Record 1989/36.

BALME B., 1989 - Australian Phanerozoic Timescales: 7.Triassic. Biostratigraphic Chart and Explanatory Notes.Bureau Mineral Resources, Australia, Record 1989/37.

BEGG, J., 1987 - Structuring and controls on Devonian reefdevelopment on the north-west Barbwire and adjacentterraces, Canning Basin. Australian Petroleum Explorationassociation Journal, 27 (1), 137-151.

BROWN, S.A., BOSERIO, I.M., JACKSON, KS. & SPENCEK.W., 1984- The Geological Evolution of the Canning Basin- Implications for Petroleum Exploration. in P.C. Purcell(Editor), The Canning Basin, W.A. Proceedings of theGeological Society of Australia and Petroleum ExplorationSociety of Australia Symposium, Perth, W.A. 1984, 85-96.

DRUCE, E.C. & RADKE, B.M., 1979 - The Geology of theFairfield Group, Canning Basin, Western Australia: BureauMineral Resources Geology and Geophysics, Australia,Bulletin 200.

DRUMMOND, B.J., ETHERIDGE, M.A., DAVIES, P.J., &MIDDLETON, M.F., 1988 - Half-graben model for thestructural evolution of the Fitzroy Trough, Canning Basin,and implications for resource exploration: AustralianPetroleum Exploration Association Journal, 28 (1) 76-86.

DRUMMOND, B.J., SEXTON, M.J., BARTON, T.J., &SHAW, R.D., 1991 - The nature of faulting along themargins of the Fitzroy Trough, and implications for thetectonic development of the trough: Exploration Geophys-ics, 22, 111-116.

GOLDSTEIN, B.A., 1989, Waxings and wanings in stra-tigraphy, play concepts and prospectivity in the CanningBasin: Australian Petroleum Exploration AssociationJournal 29 (1) 466-508.

HALL, W.D.M., 1984, The stratigraphic and structuraldevelopment of the Givetian-Frasnian reef complex,Limestone Billy Hills, western Pillara Range, W.A.: in P.G.Purcell (Editor), The Canning Basin, W.A. Proceedings ofthe Geological Society of Australia and Petroleum Explor-ation Society of Australia Symposium, Perth, W.A. 1984,215-222.

HURLEY, N.F. & LOHMANN, K.C., 1989 - Diagenesis ofDevonian reefal carbonates in the Oscar range, Canningbasin, Western Australia: Journal of Sedimentary Petrology,59, 127-146.

JACKSON, M.J., DIEKMAN, L.J., KENNARD, J.M., SOU-THGATE, P.N., O'BRIEN, P.E., & SEXTON, M.J., 1992 -Sequence stratigraphy of the Devonian-Carboniferous ofthe Canning Basin and its use in the identification of basinfloor fans and other petroleum plays. Australian PetroleumExploration Association Journal, 32, 214-230.

JONES, P.J., 1989 - Australian Phanerozoic Timescales: 5.Carboniferous. Biostratigraphic Chart and ExplanatoryNotes. Bureau Mineral Resources, Record 1989/35.

JONES, P.J., & YOUNG, G.C., in prep. - Updated biostrat-igraphic summaries of selected wells on the Lennard Shelf,in Jones, P.J., and Young, G.C. (eds.,), Overview of Phaner-ozoic Biostratigraphy and Paleontology of the CanningBasin (Lennard Shelf), Appendix. Australian GeologicalSurvey Organisation, Record 1992/98.

KEMP, G.J., & WILSON, B.L, 1990- The seismic expressionof Middle to Upper Devonian reef complexes, CanningBasin. Australian Petroleum Exploration AssociationJournal, 30 (1), 280-289.KENNARD, J.M., SOUTHGATE, P.N., JACKSON, M.J.,O'BRIEN, P.E., CHRISTIE-BUCK, N., HOLMES, A.E., &SARG, J.F., 1992 - A new sequence perspective on theDevonian reef complex and the Frasnian-Famennianboundary, Canning Basin, Australia. Geology, 20, 1135-1138.

KERANS, C, HURLEY, N.F., & PLAYFORD, P.E., 1986 -Marine diagenesis in Devonian reef complexes of theCanning basin, Western Australia, in J.H. Schroeder andB.H. Purser, eds., Reef Diagenesis: Springer-Verlag,Berlin, 357-380.

PLAYFORD, P.E, 1980 - Devonian "Great Barrier Reef' ofthe Canning Basin, Western Australia: AmericanAssociation of Petroleum Geologists Bulletin, 64, 814-840.

PLAYFORD, P.E„ 1982 - Devonian reef prospects in theCanning Basin: implications of the Blina oil discovery,Australia Petroleum Exploration Association Journal, 22,258-271.

PLAYFORD, P.E., 1984 - Platform-margin and marginal-slope relationships in Devonian reef complexes of theCanning Basin, in Purcell, P.C., ed, The Canning Basin,Western Australia: Proceedings of the Geological Society ofAustralia and Petroleum Exploration Society of AustraliaSymposium, 190-214.

PLAYFORD, P.E., & LOWRY, D.C., 1966 - Devonian reefcomplexes of the Canning Basin, Western Australia:Geological Survey of Western Australia Bulletin 118,150 p.

PLAYFORD, P.E., HURLEY, N.F., KERANS, C., &MIDDLETON, M.F., 1989 - Reefal platform development,Devonian of the Canning Basin, Western Australia, inCrevello P.D. and others, eds., Controls on CarbonatePlatform and Basin Development Society of EconomicPaleontologists and Mineralogists Special Publication 44,187-202.

POSAMENTIER, H.W., JERVEY, M.T., & VAIL, P.R., 1988 -Eustatic controls on clastic deposition I - Conceptualframework, in Wilgus, C.K., and others, eds., Sea-levelChanges: An Integrated Approach: Society of EconomicPaleontologists and Mineralogists Special Publication 42,109-124.

POSAMENTIER, H.W., & VAIL, P.R., 1988 - Eustaticcontrols on elastic deposition H - Sequence and systemstract models, in Wilgus, C.K., and others, eds., Sea-levelChanges: An Integrated Approach: Society of EconomicPaleontologists and Mineralogists Special Publication 42,125-154.

PURCELL, P.C., 1984 - The Canning Basin, W.A. Proceed-ings of the Geological Society of Australia and PetroleumExploration Society of Australia Symposium, Perth, W.A.1984.


17

PURCELL, P.C., & POLL, J., 1984 - The seismic definitionof the main structural elements of the Canning Basin: inP.G. Purcell (Editor), The Canning Basin, W.A. Proceed-ings of the Geological Society of Australia and PetroleumExploration Society of Australia Symposium, Perth, W.A.1984, 73-84.

RATTIGAN, J.H., 1967- Fold and fracture patterns result-ing from basement wrenching in the Fitzroy Depression,Western Australia. Proceedings of the Australasian Instituteof Mining and Metallurgy, 223, 17-22.

READ, J.F., 1985 - Carbonate platform fades models.American Association of Petroleum Geology Bulletin, 69, 1-21.

SARG, J.F., 1988, Carbonate sequence stratigraphy, inWilgus, C.K., and others, eds., Sea-level Changes: AnIntegrated Approach: Society of Economic Paleontologistsand Mineralogists Special Publication 42, 155-181.

SHAW, R.D., SEXTON, M.J. & ZEIL1NGER, I, in prep. -The tectonic framework of the Canning Basin. AustralianGeological Survey Organisation, Record.

SOUTHGATE P.N., KENNARD, J.N., JACKSON M.J.,O'BRIEN, P.E. & SEXTON, M.J., 1993- Reciprocal lowstandclastic and highstand carbonate sedimentation, subsurfaceDevonian Reef Complex, Canning Basin, Western Australia.in Loucks, R., & Sarg, J.F.,(Eciitors), Recent Advances andApplications of Carbonate Sequence Stratigraphy. AAPGMemoir (in press).

TOWNER R.R., 1981 - Derby, Western Australia, 1:250 000Geological Series, Second Edition. Bureau of MineralResources, Australia, Explanatory Notes SE/51-7.

VAIL, P.R., 1987- Seismic stratigraphy interpretation usingsequence stratigraphy, Patti: Seismic stratigraphy interpre-tation procedure, in Bally, A.W., ed., Atlas of seismicstratigraphy: American Association of Petroleum Geolo-gists, Studies in Geology, v. 27, pt. 1, 1-10.

VAN WAGONER, J.C, MITCHUM, RM., CAMPION,K.M., & RAHMANIAN, V.D., 1990 - Siliciclastic sequencestratigraphy in well logs, cores, and outcrops: concepts forhigh-resolution correlation in time and space. AmericanAssociation of Petroleum Geologists Methods in Explor-ation Series, 7, 55p.

WALLACE, M.W., !GRANS, M.W, PLAYFORD, P.E., &MCMANUS, A., 1991 - Burial cliagenesis in the UpperDevonian reef complexes of the Geilde Gorge region,Canning basin, Western Australia: American Association ofPetroleum Geologists Bulletin, 75, 1018-1038.

WEBBY, B.D. & NICOLL, RS., 1989 - Australian Phaner-ozoic Timescales: 2. Ordovician. Biostatigraphic Chart andExplanatory Notes. Bureau Mineral Resources, Australia,Record 1989 /32.

WORNHARDT, W.W., (Compiler), 1991 - Sequence stra-tigraphy concepts and applications (Wall Chart), Version1.0: Micro-Strat Inc., Houston.

YEATES, A.N., GIBSON, D.L., TOVVNER,R.R. & CROWE,R.W.A., 1984 - Regional geology of the onshore CanningBasin, W.A., In Purcell, P.C. (Editor), The Canning Basin,W.A. Proceedings of the Geological Society of Australiaand Petroleum Exploration Society of Australia Sympo-sium, Perth, 1984, 23-55.

YOUNG, G.C. 1989 - Australian Phanerozoic Tunescales: 4.Devonian. Biostratigraphic Chart and Explanatory Notes.Bureau Mineral Resources, Australia, Record 1989/34.


18

FIGURES


124°50'

Van EmmerickConglomerate

124°10 E 124°30'

17°10'S —

125°10'

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All

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--II,. Seismic lines depicted in Fig.2

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-0^Exploration well

•I•••■••1;OM WNW II••■■•■••■

19

Figure 1. Study area showing seismic lines, wells, principal structural elements andoutcropping Devonian reef complex. ME - Meda Embayment, BH - Blackstone High,KDE - Kimberley Downs Embayment.

-----------------------------AUSTRALIAN GEOLOGICAL SURVEY ORGANISATION

Highstand &Transgressive

Prograding complex

Slope fan

Basin floor fan

FITZROY TROUGHLowstand^ Meda 1

LENNARD SHELF

TOURNAISIAN

^ Sequence boundary- - - - Systems tract boundary- Fault

^

.^Platform margin• • Frasnian - Famennian

boundary

^

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20

Figure 2. Line diagram depicting sequence and systems tract development in theMeda Embayment. Note coastal onlap of the Frasnian-Famennian sequence (arrow).


-

MANN.

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16

17

Figure 3.Sequence and systems tractinterpretation of the Devonian-Carboniferous reef and rampcomplex; Seismic line 11131-22,Kimberley Downs Embayment.

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Figure 4. Relative tectonic-eustatic curve for the Givetian-Tournaisian succession on the Laurel DownsTerrace and adjacent Fitzroy Trough in the Meda area, showing the major transgressive-regressive CT -

R) facies cycle (smooth curve) and the shorter wavelength third order relative sea level cycles. In theregressive half cycle the curves are offset by fault-movements and erosion in the latest Frasnian andthe early Famennian. The dashed curves are corrected for these movements. Note the three second-order accommodation cycles in the regressive half cycle with maximum flooding surfaces in Famenniansequence 2A and Tournaisian sequences 1 & 6 (heavy arrows). Recent biostratigraphic data indicatesan early Tournaisian age for Famennian sequences 3B and 4.


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11/E61/12

SYSTEMS TRACTS

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Shelf margin

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Meda 1

Figure 5. Sequence model of the Frasnian-Famennian reef complex based on seismic and welldata in the Meda area (location of Meda 1 is an approximation). Facies are shown fortransgressive and highstand deposits.

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it/E51/12

Meda 1

Figure 5. Sequence model of the Frasnian-Famennian reef complex based on seismic and welldata in the Meda area (location of Meda 1 is an approximation). Facies are shown fortransgressive and highstand deposits.

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CAIG ASI OEC SAGE 1 EA SE EAAOY OES o SEISMIC a MA · PDF fileSAGE 1 EA SE EAAOY OES o SEISMIC...

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