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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 65 (1981)

Issue: 4. (April)

First Page: 767

Last Page: 767

Title: Geologic Processes in Evaporites in Northern Delaware Basin: ABSTRACT

Author(s): Dennis W. Powers

Article Type: Meeting abstract


Permian evaporites of the northern Delaware basin have been studied in detail for the Waste Isolation Pilot Plant (WIPP). The WIPP is proposed for the disposal of defense radioactive waste in the Salado Formation about 30 mi (48 km) east of Carlsbad.

Boreholes in the northern part of the WIPP site confirm unusual bed thicknesses and attitudes in the Castile Formation. The Castile is ordinarily nearly flat and consists of three anhydrites and two interbedded halites with a total thickness of about 1,350 ft (411 m). WIPP 13 encountered 900 ft (274 m) between the top of Castile and total depth about 50 ft (15 m) into the lower anhydrite. The upper anhydrite dips as much as 40° and contains a small recumbent fold. The thinning and structure also occur in the lower Salado. The same stratigraphic interval in WIPP 11 is 1,230 ft (575 m) thick. The upper anhydrite at WIPP 11 is very thin (< 80 ft or 24 m) and arches; the halite below it is over 900 ft (274 m) thick. the lower Salado beds arch over the Castile. The top of the Salad Formation is not arched at either borehole. Other Castile beds in each hole vary in thickness to lesser degrees.

The major hypotheses for the origin of these features are deposition, dissolution, and halokinesis. Laminated anhydrite does not form on 40° dips. Dissolution residues do not account for thin halite beds. Delicate primary halite structures in the upper Castile in WIPP 13 should not survive later massive halokinesis. Synsedimentary deformation is invoked as a possible explanation. Investigations continue.

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