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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 60 (1976)

Issue: 12. (December)

First Page: 2162

Last Page: 2166

Title: Origin of Gulf Coast Salt-Dome Cap Rock: GEOLOGIC NOTES

Author(s): Charles W. Walker (2)


More than half of the proved domes in the Gulf Coast area are known to have cap rock which is composed chiefly of anhydrite, calcite, gypsum, and locally celestite. A detailed study of cap rock from 39 salt domes as well as a thorough literature search on the subject indicates large lithologic and chemical variations in its character. The two most widely accepted theories of origin--(1) residual accumulation and secondary alteration of the less soluble minerals contained in the salt, and (2) precipitation in place--cannot satisfactorily account for these variations in cap rock and its relation to the surrounding environment.

It is proposed here that these variations may be explained by a "modified precipitation in place" theory in which most of the cap rock was precipitated from ascending solutions rich in calcium sulfate, and a smaller amount was contributed by dissolution of the upper salt surface which released the less soluble residue.

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Fig. 1. Location of salt domes included in study.

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