Deformation of evaporites near the Waste Isolation Pilot Plant (WIPP) site
Layered evaporite units of Ochoan age in the Delaware Basin are 1000 m thick. They are divided into three stratigraphic units (listed in order of increasing age): the Rustler Formation, the Salado Formation, the Castile Formation. These units, especially the Castile, are deformed along portions of the margin of the Delaware Basin and in some areas internal to the basin. Hypotheses of origin of deformation considered are: gravity foundering; gravity sliding; gypsum dehydration; dissolution; and depositional variations. Gravity foundering and sliding are considered the most probable causes of deformation. However, no hypothesis adequately answers why the deformation has a limited areal distribution. A possible explanation would be areal variations in rock strength caused by variations of intergranular water content. Age and timing of deformation are also crucial. Standard stratigraphic arguments based on superposition may not apply to such a highly incompetent material as halite. Gravity foundering could have happened at any time since deposition including the present; gravity sliding would probably have occurred since basin tilting began in the Cenozoic. Deformation could be ongoing. However, the strain rates are such (10/sup -16/ s/sup -1/) that deformation would progress slowly relative to the facility's time frame of 2.5 x 10/sup 5/ y. Deformation of Salado units would be minimal (<10 m) or nonexistent, but within this time frame, upper anhydrite units of the Castile could fracture and provide the volume for a brine reservoir. Such Volumes would be small (<1%) and would require 10/sup 4/ to 10/sup 6/ y to develop. At these strain rates, fractures that connect the fractured anhydrites of the Castile with the middle Salado could not develop. Deformation should not directly jeopardize the facility over the next 2.5 x 10/sup 5/ y.
- Research Organization:
- Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Texas Univ., El Paso (USA). Dept. of Geological Sciences; US Geological Survey, Denver, CO (United States)
- DOE Contract Number:
- AC04-76DP00789
- OSTI ID:
- 6467937
- Report Number(s):
- SAND-82-1069; ON: DE83011025
- Resource Relation:
- Other Information: Portions are illegible in microfiche products. Original copy available until stock is exhausted
- Country of Publication:
- United States
- Language:
- English
Similar Records
The geologic structures observed in drillhole DOE-2 and their possible origins: Waste Isolation Pilot Plant
Marker Bed 139: a study of drillcore from a systematic array. [Salado Formation]
Related Subjects
58 GEOSCIENCES
EVAPORITES
DEFORMATION
BOREHOLES
EXPERIMENTAL DATA
GEOPHYSICAL SURVEYS
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RADIOACTIVE WASTE FACILITIES
SALT DEPOSITS
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FEDERAL REGION VI
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NUMERICAL DATA
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SEDIMENTARY ROCKS
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