Dissolution of halite and gypsum, and hydration of anhydrite to gypsum, Rustler Formation, in the vicinity of the Waste Isolation Pilot Plant, southeastern New Mexico

Snyder, R.P.

doi:10.3133/ofr85229

Cited by 12 publications

(13 citation statements)

References 5 publications

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“…During that time it has been reduced in thickness by dissolution of the more soluble beds in the formation. Various authors (e.g., Snyder and Gard, 1982;Snyder 1985;Chaturvedi and Channell, 1985) have suggested that this process of thinning by dissolution continues eastward into the subsurface, encroaching on the WIPP site. These authors suggest that more halite, progressively deeper in the Rustler section, has been dissolved westward, the closer one gets to Nash Draw (Figure 14, Figure 15).…”

Section: Cross Section Evidencementioning

confidence: 99%

“…At 309 ft thick in the shafts, the Rustler Formation is 176 ft (36%) thinner than the measured 485 ft Rustler thickness in a well located five miles east (see the isopach maps in Holt and Powers, 1988), part of an overall westward thinning trend. Moreover, the shafts are located in the zone where Snyder (1985) specifically suggested that halite was removed by subsurface dissolution from both the middle (Tamarisk) and upper (Forty-niner) Members of the Rustler Formation. Although dissolution was invoked by Snyder as the mechanism that caused both thinning of the formation and the absence of halite, the evidence he presented for that interpretation is circular in that it consisted only of 1) the fact that the Rustler Formation thins westward, 2) that it contains little halite in the western locations, and 3) the inference that much of the anhydrite has been converted to gypsum.…”

Section: Evidence From the Shaftsmentioning

confidence: 99%

“…Hill (1999), drawing on a theory advocated by Snyder (1985) and Snyder and Gard (1982), suggests that thinning of the Rustler Formation in the vicinity of the WIPP site must be related to dissolution since the thinning trend continues westward to where the Rustler has been markedly and demonstrably thinned by dissolution in Nash Draw. Although dissolution is an obvious process Figure 13.…”

Section: Stratigraphic Thinning Of the Rustler Formation And "Missingmentioning

confidence: 99%

“…Definitive primary sedimentary structures found in siltstone and clay units that had previously been interpreted as dissolution residues 2. An absence of dissolutionindicator breccias and disrupted bedding in the Tamarisk and Forty-niner Members, the two members, according to Snyder's (1985) model where dissolution should have been most prominent 3. The overwhelming dominance of anhydrite in the Tamarisk and Forty-niner Members, unconverted to gypsum as would be expected if there had been sufficient water to remove significant thicknesses of halite.…”

Section: Evidence From the Shaftsmentioning

confidence: 99%

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Assessment of the potential for karst in the Rustler Formation at the WIPP site.

Lorenz¹

2006

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This report is an independent assessment of the potential for karst dissolution in evaporitic strata of the Rustler Formation at the Waste Isolation Pilot Plant (WIPP) site. Review of the available data suggests that the Rustler strata thicken and thin across the area in depositional patterns related to lateral variations in sedimentary accommodation space and normal facies changes. Most of the evidence that has been offered for the presence of karst in the subsurface has been used out of context, and the different pieces are not mutually supporting.Outside of Nash Draw, definitive evidence for the development of karst in the Rustler Formation near the WIPP site is limited to the horizon of the Magenta Member in drillhole WIPP-33. Most of the other evidence cited by the proponents of karst is more easily interpreted as primary sedimentary structures and the localized dissolution of evaporitic strata adjacent to the Magenta and Culebra water-bearing units. Some of the cited evidence is invalid, an inherited baggage from studies made prior to the widespread knowledge of modern evaporite depositional environments and prior to the existence of definitive exposures of the Rustler Formation in the WIPP shafts. Some of the evidence is spurious, has been taken out of context, or is misquoted.Lateral lithologic variations from halite to mudstone within the Rustler Formation under the WIPP site have been taken as evidence for the dissolution of halite such as that seen in Nash Draw, but are more rationally explained as sedimentary facies changes. Extrapolation of the known karst features in Nash Draw eastward to the WIPP site, where conditions are and have been significantly different for half a million years, is unwarranted. The volumes of insoluble material that would remain after dissolution of halite would be significantly less than the observed bed thicknesses, thus dissolution is an unlikely explanation for the lateral variations from halite to mudstone and siltstone. 4Several surficial depressions at WIPP, suggested to be sinkholes, do not have enough catchment area to form a sinkhole, and holes drilled to investigate the subsurface strata do not support a sinkhole interpretation. Surface drainage across the WIPP site is poorly developed because it has been disrupted by migrating sand dunes and because precipitation is not focused by defined catchment areas in this region of low precipitation and low-dip bedding, not because it has been captured by sinkholes. There are no known points of discharge from the Rustler Formation at WIPP that would indicate the presence of a subsurface karst drainage system. The existing drillholes across the WIPP site, though small in diameter, are sufficient to assess the probability of karst development along the horizontal fractures that are common in the Rustler Formation, and the area of investigation has been augmented significantly by the mapping of four large-diameter shafts excavated into the WIPP repository. The general absence of dissolution, karsting, and related con...

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Section: Cross Section Evidencementioning

confidence: 99%

Section: Evidence From the Shaftsmentioning

confidence: 99%

Section: Stratigraphic Thinning Of the Rustler Formation And "Missingmentioning

confidence: 99%

Section: Evidence From the Shaftsmentioning

confidence: 99%

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Assessment of the potential for karst in the Rustler Formation at the WIPP site.

Lorenz¹

2006

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“…The geology and hydrogeology of the Gnome site are described by Gard (1968), Cooper (1962a), Cooper (1962b), and Cooper and Glanzman (197 1); data regarding the Culebra Dolomite from investigations at the Waste Isolation Pilot Plant (WIPP) site, located approximately 10 km northeast of the Gnome site (Figure l), are provided by Cauffman et al (1990), Lowenstein (1987), andSnyder (1985); and Pohlmann and Andricevic (1994) model the migration of tritium introduced into the Culebra by the tracer test.…”

Section: Hydrogeologic Settingmentioning

confidence: 99%

Assessment of hydrologic transport of radionuclides from the Gnome underground nuclear test site, New Mexico

Earman¹,

Chapman²,

Pohlmann³

et al. 1996

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Geochemical evidence for transient karstic water/rock interaction in evaporites of the northern Delaware Basin, New Mexico, USA

Lambert

1997

Carbonates Evaporites

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Permianevaporitesin thenorthernDelaware Basin (southeastern New Mexico)have experienced varyingdegreesof water! rock interaction, locallyresultingin karsticlandforms such as topographic depressions, sinkholes, andblindvalleys. MeteoricgroWldwaters and the rocks with which they have interacted bear geochemical signatures that delineatesuch interactions even in the absenceof surficial indicators. Based on fresh-water potentiometric heads alone,hydraulically confinedgroundwater appears to flow north to south, at steady state acrossthe site of the Waste IsolationPilot Plant (WIPP),but freshens from an ionic strengthof 0.3-1.6to <0.1 molal southof the site. This abruptchangein hydrochemical facies is not causedby youngervertical rechargepreferentially occurring in the south;residence times basedon radiocarbon (-14 ka) of less salineCa-S0 4 watersin the south are no shorterthan those of more saline Na-O watersin the north. 234UfDlU activity ratios (AR.'s)moIlOtonically increasefrom westtoeast,correlative witha 1000decrease in fracture-permeability, butnormal to the that of inferredmodem flow. Preservation of high A.R. 's argues againstrapidoxic rechargefrom shallowerunits, Thesegeochemical constraints suggest that modern groundwater flow is transient, and that the originalpaleoflow direction at the time of rechargein the late Pleistocene had a significantwest-to-east component, The geochemical recordof paleoflow hasnot yet been obliteratedby Dareianflow, whereas thepotentiometric contourshaveresponded to post-Pleistocene potentiometric changes. The recordsof interactions between these groundwaters and adjacentevaporiterocks are preservedin the characteristic~Srf'6Sr ratios of gypsumalteredfrom anhydrite and the .'O! 16() ratiosof calcitealteredfromdolomite. These zonesof alteration occurring at lessthan 300m depthareinterbedded withlessalteredzones bearinggeochemical signaturesmorecharacteristic of marineevaporites, suggesting stratabound ratherthan verticalflow. Combinations of these geochemical parameters provide the basis for distinguishing hydrologic regimes in which the water/rock ratios have been higher (karstic) from those where evaporitedissolution hasbeen less active.

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Dissolution of halite and gypsum, and hydration of anhydrite to gypsum, Rustler Formation, in the vicinity of the Waste Isolation Pilot Plant, southeastern New Mexico

Cited by 12 publications

References 5 publications

Assessment of the potential for karst in the Rustler Formation at the WIPP site.

Assessment of the potential for karst in the Rustler Formation at the WIPP site.

Assessment of hydrologic transport of radionuclides from the Gnome underground nuclear test site, New Mexico

Geochemical evidence for transient karstic water/rock interaction in evaporites of the northern Delaware Basin, New Mexico, USA

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