Petrographic study of evaporite deformation near the Waste Isolation Pilot Plant (WIPP)
The Delaware Basin of southeastern New Mexico contains about 1000 m of layered evaporites. Areas in the northern Delaware Basin, bordering the Capitan reef, have anomalous seismic reflection characteristics, such as loss in reflector continuity. Core from holes within this zone exhibits complex mesoscopic folds and extension structures. On a larger scale, anticlines and synclines are indicated by structure contours based on boreholes. The deformation is probably gravity-driven. Such a process is initiated by basin tilting during either a Mesozoic or Cenozoic period of uplift. Small-scale structures suggest that deformation was episodic with an early, syndepositional stage of isoclinal folding. Later, open-to-tight asymmetric folding is more penetrative and exhibits a sense of asymmetry opposite to that of the earlier isoclinal folding. The younger folds are associated with development of zonal crenulation cleavage and microboundinage of more competent carbonate layers. At the same time, halite beds developed dimensional fabrics and convolute folds in anhydrite stringers. Late-stage, near-vertical fractures formed in competent anhydrite layers. Microscopic textures exhibit rotated anhydrite porphyroblasts, stress shadow growth, and microboundinage. Except during late-stage deformation, anhydrite and halite recrystallized synkinematically. Drastic strength reduction in anhydrites through dynamic recrystallization occurs experimentally near 200/sup 0/C. However, evaporites of the WIPP site never experienced temperatures > 40/sup 0/C. Microscopic fabrics and P, T history of the evaporites suggest that pressure solution was the active mechanism during deformation of evaporites at the WIPP site.
- Research Organization:
- Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
- DOE Contract Number:
- AC04-76DP00789
- OSTI ID:
- 6057593
- Report Number(s):
- SAND-83-0166; ON: DE83014796
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
58 GEOSCIENCES
EVAPORITES
DEFORMATION
PETROGRAPHY
NEW MEXICO
RADIOACTIVE WASTE DISPOSAL
SALT DEPOSITS
FEDERAL REGION VI
GEOLOGIC DEPOSITS
MANAGEMENT
NORTH AMERICA
ROCKS
SEDIMENTARY ROCKS
USA
WASTE DISPOSAL
WASTE MANAGEMENT
052002* - Nuclear Fuels- Waste Disposal & Storage
580300 - Mineralogy
Petrology
& Rock Mechanics- (-1989)