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Pulses of carbon dioxide emissions from intracrustal faults following climatic warming Supplementary Information: Green River Natural CO2 Analogue Site

CO2-charged fluids, discharging almost pure CO2 gas [95.7-99.4 % CO2; 3.4-0.5 % N2;

0.1-0.9 % O2, 0.01-0.05 % Ar; 0.00-0.01 % He; Ref 7], escape to the surface along Little

Grand Wash Fault and Salt Wash Graben, and from abandoned petroleum exploration

and water wells in the vicinity of Green River, Utah, USA (Figure S1). A number of

studies have examined various aspects of the origin of the carbon dioxide and effused

groundwaters7,51,52, CO2 promoted fluid-mineral reactions in the groundwater system2, the

nature and magnitude of CO2 leakage from this site53, rates of CO2 effusion from the

largest of the CO2 degassing geysers6,54,55, and the role of the local structure and fault

architecture on controlling the sites of CO2 leakage5,10.

Salt Wash and Tenmile Graben are together about 31 km long and are separated

by a step-over zone. The faults strike about N 70° W. At least some movement of these

faults may be related to salt flowage through the Permian to mid Jurassic56. Local

sedimentation patterns reveal a period of salt movement between Triassic to mid Jurassic

resulting in the development of the Green River anticline and adjacent Courthouse

Syncline57. Some fault movement may also be due to interaction of the Uncompahgre and

San Rafael blocks to the east and west, respectively56. Unpublished illite age analysis

dates initial fault movement at 40 ±10 Ma corresponding to the early tertiary Laramide

orogeny57. Where the footwall Upper Jurassic units are juxtaposed against shales in the

hanging-wall, the fault core is dominated by low-permeability clay-rich gouge57.

Conversely, the surrounding damage zone is dominated by fractures both in the high

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SUPPLEMENTARY INFORMATION DOI: 10.1038/NGEO1451

permeability reservoir units and in the low-permeability seal unit10. Fracture orientation

range and frequency are enhanced in zones of structural complexity improving fracture

connectivity and providing pathways for fluids to migrate vertically, parallel to the

fault10. Ref 10 assessed sealing mechanisms of the faults and concluded that cross-fault

flow should occur at low-throws (<100 m), towards the fault tips but that the faults were

sealed at higher throws (>100 m), towards the axis of the Green River anticline, due to

reservoir–non-reservoir juxtaposition and development of a continuous clay smear (Fig

S3). Hydraulic head measurements of fluid in the Navajo Sandstone map fluid flow

pathways parallel to the length of the fault, where it is sealing (Fig S1).

Travertine mounds are distributed along the length of both Little Grand Wash

Fault and Salt Wash Graben where they intersection the apex of the Green River anticline

(Figure S2). The distribution of travertine along each fault corresponds approximately to

the limits of the fault closure, being bracketed by the juxtaposition spill point (Figure S3).

This suggests that leakage has occurred from a free CO2 gas cap and that the location of

the leakage sites is dependent on the distribution of free gas. As travertine mounds grow

they develop a constant surface area-thickness relationship (Figure S4 & S5). Detailed

analysis of two veins (Figure S6) reveals systematic trends in δ13C and δ18O from vein

centre to edge, in the direction of growth.

Supplementary References

51 Baer, J. & Rigby, J. Geology of the Crystal Geyser and environmental implications of

its effluent, Grand County, Utah. Utah Geological and Mineral Survey Utah Geology,

125–130, (1978).

52 Gilfillan, S. Deep magmatic degassing and the Colorado Plateau uplift PhD thesis,

Univeristy of Manchester, UK, (2006).

53 Allis, R. et al. Implications of results from CO2 flux surveys over known CO2

systems for long-term monitoring. United States Geological Survey, (2005).

54 Gouveia, F. & Friedmann, S. Timing and prediction of CO2 eruptions from Crystal

Geyser, UT. United States. Dept. of Energy., (2006).

55 Gouveia, F., Johnson, M., Leif, R. & Friedmann, S. Aerometric measurement and

modeling of the mass of CO2 emissions from Crystal Geyser, Utah. UCRL-TR-

211870, Lawrence Livermore National Lab., Livermore, CA (USA). (2005).

56 Doelling, H. Geology of Salt Valley Anticline and Arches National Park, Grand

County, Utah. Salt deformation in the Paradox region, Utah. Utah Geological and

Mineral Survey Bulletin, 1–60, (1988).

57 Dockrill, B. Understanding Leakage from a Fault Sealed CO2 Reservoir in East

Central Utah: A Natural Analouge Applicable to CO2 Storage PhD thesis, University

of Dublin, Trinity College, Ireland, (2005).

58 Doellling, H., Ross, M. & Mulvey, W. Geologic Map of the Moab 7.5’Quadrangle,

Grand County, Utah. Utah Geological Survey Map 181, (2002).

59 Hood, J. & Patterson, D. Bedrock aquifers in the northern San Rafael Swell area.

Utah, with special emphasis on the Navajo Sandstone. State of Utah Department of

Natural Resources Technical Publication 78, (1984).

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permeability reservoir units and in the low-permeability seal unit10. Fracture orientation

range and frequency are enhanced in zones of structural complexity improving fracture

connectivity and providing pathways for fluids to migrate vertically, parallel to the

fault10. Ref 10 assessed sealing mechanisms of the faults and concluded that cross-fault

flow should occur at low-throws (<100 m), towards the fault tips but that the faults were

sealed at higher throws (>100 m), towards the axis of the Green River anticline, due to

reservoir–non-reservoir juxtaposition and development of a continuous clay smear (Fig

S3). Hydraulic head measurements of fluid in the Navajo Sandstone map fluid flow

pathways parallel to the length of the fault, where it is sealing (Fig S1).

Travertine mounds are distributed along the length of both Little Grand Wash

Fault and Salt Wash Graben where they intersection the apex of the Green River anticline

(Figure S2). The distribution of travertine along each fault corresponds approximately to

the limits of the fault closure, being bracketed by the juxtaposition spill point (Figure S3).

This suggests that leakage has occurred from a free CO2 gas cap and that the location of

the leakage sites is dependent on the distribution of free gas. As travertine mounds grow

they develop a constant surface area-thickness relationship (Figure S4 & S5). Detailed

analysis of two veins (Figure S6) reveals systematic trends in δ13C and δ18O from vein

centre to edge, in the direction of growth.

Supplementary References

51 Baer, J. & Rigby, J. Geology of the Crystal Geyser and environmental implications of

its effluent, Grand County, Utah. Utah Geological and Mineral Survey Utah Geology,

125–130, (1978).

52 Gilfillan, S. Deep magmatic degassing and the Colorado Plateau uplift PhD thesis,

Univeristy of Manchester, UK, (2006).

53 Allis, R. et al. Implications of results from CO2 flux surveys over known CO2

systems for long-term monitoring. United States Geological Survey, (2005).

54 Gouveia, F. & Friedmann, S. Timing and prediction of CO2 eruptions from Crystal

Geyser, UT. United States. Dept. of Energy., (2006).

55 Gouveia, F., Johnson, M., Leif, R. & Friedmann, S. Aerometric measurement and

modeling of the mass of CO2 emissions from Crystal Geyser, Utah. UCRL-TR-

211870, Lawrence Livermore National Lab., Livermore, CA (USA). (2005).

56 Doelling, H. Geology of Salt Valley Anticline and Arches National Park, Grand

County, Utah. Salt deformation in the Paradox region, Utah. Utah Geological and

Mineral Survey Bulletin, 1–60, (1988).

57 Dockrill, B. Understanding Leakage from a Fault Sealed CO2 Reservoir in East

Central Utah: A Natural Analouge Applicable to CO2 Storage PhD thesis, University

of Dublin, Trinity College, Ireland, (2005).

58 Doellling, H., Ross, M. & Mulvey, W. Geologic Map of the Moab 7.5’Quadrangle,

Grand County, Utah. Utah Geological Survey Map 181, (2002).

59 Hood, J. & Patterson, D. Bedrock aquifers in the northern San Rafael Swell area.

Utah, with special emphasis on the Navajo Sandstone. State of Utah Department of

Natural Resources Technical Publication 78, (1984).

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Figure S1 Surface geology of the Green River anticline. The map shows the clustering of springs along the axis of the anticline, within the damage zones of the Little Grand Wash Fault and the northern fault of Salt Wash Graben. The northerly plunging Green River anticline is transected by the east-west trending Little Grand Wash fault and northeast-southwest Salt Wash Graben. Travertine outcrops are found along each fault where they intersect the crest of the anticline (boxed areas). Groundwater flow paths in the Navajo Sandstone are deflected by the normal faults where throws exceed ~100m. Redrawn after Ref 58,59. Shown below is a north-south cross section along the apex of the anticline.

Figure S2 Map showing the distribution of travertine mounds within the footwall wall of the northern fault of Salt Wash Graben (redrawn after Ref 57). Labels are the age obtained from each mound and the 2σ uncertainty.

Figure S3 Schematic diagram showing the approximate geometry of the CO2 reservoir and sites of CO2 leakage being controlled by the limits of the CO2 gas cap, which in itself is controlled by the spill point defined by the limits of reservoir-seal juxtaposition. Redrawn after Ref 5.

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Figure S1 Surface geology of the Green River anticline. The map shows the clustering of springs along the axis of the anticline, within the damage zones of the Little Grand Wash Fault and the northern fault of Salt Wash Graben. The northerly plunging Green River anticline is transected by the east-west trending Little Grand Wash fault and northeast-southwest Salt Wash Graben. Travertine outcrops are found along each fault where they intersect the crest of the anticline (boxed areas). Groundwater flow paths in the Navajo Sandstone are deflected by the normal faults where throws exceed ~100m. Redrawn after Ref 58,59. Shown below is a north-south cross section along the apex of the anticline.

Figure S2 Map showing the distribution of travertine mounds within the footwall wall of the northern fault of Salt Wash Graben (redrawn after Ref 57). Labels are the age obtained from each mound and the 2σ uncertainty.

Figure S3 Schematic diagram showing the approximate geometry of the CO2 reservoir and sites of CO2 leakage being controlled by the limits of the CO2 gas cap, which in itself is controlled by the spill point defined by the limits of reservoir-seal juxtaposition. Redrawn after Ref 5.

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Figure S4 Illustration of travertine mound and aragonite vein growth. CO2-charged waters flow through fault parallel fractures in the fault damage zone of the Entrada and Curtis Sandstones. Travertine mounds grow from CO2-charged waters by the successive deposition of carbonate layers at the surface. As time proceeds (1-7) the mounds develop topography and spread laterally, developing a constant surface area-thickness relationship. Near the surface CO2-charge fluid migrates laterally from the fault damage zone, beneath low permeability silty intercalations in the host rock, precipitating bedding parallel aragonite veins in the fault footwall. Redrawn after Ref 16.

Figure S5 Thickness-surface area relationship for twelve well exposed travertine mounds from Salt Wash Graben. Surface areas and thickness are estimated from field mapping.

Figure S6 Photographs of anticentripetal aragonite veins analyzed in detail. Red dots show the location of drill point from which samples were collected. Below each image are the profiles in δ13C and δ18O showing trends of increasingly heavy isotopic compositions from vein centre to edge. Data is presented in Supplementary Data Table 2.

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Figure S4 Illustration of travertine mound and aragonite vein growth. CO2-charged waters flow through fault parallel fractures in the fault damage zone of the Entrada and Curtis Sandstones. Travertine mounds grow from CO2-charged waters by the successive deposition of carbonate layers at the surface. As time proceeds (1-7) the mounds develop topography and spread laterally, developing a constant surface area-thickness relationship. Near the surface CO2-charge fluid migrates laterally from the fault damage zone, beneath low permeability silty intercalations in the host rock, precipitating bedding parallel aragonite veins in the fault footwall. Redrawn after Ref 16.

Figure S5 Thickness-surface area relationship for twelve well exposed travertine mounds from Salt Wash Graben. Surface areas and thickness are estimated from field mapping.

Figure S6 Photographs of anticentripetal aragonite veins analyzed in detail. Red dots show the location of drill point from which samples were collected. Below each image are the profiles in δ13C and δ18O showing trends of increasingly heavy isotopic compositions from vein centre to edge. Data is presented in Supplementary Data Table 2.

© 2012 Macmillan Publishers Limited. All rights reserved.