About This Item

Share This Item

The AAPG/Datapages Combined Publications Database

AAPG Special Volumes

Abstract


Pub. Id: A001 (1926)

First Page: 50

Last Page: 86

Book Title: SP 1: Geology of Salt Dome Oil Fields

Article/Chapter: Petrography of Salt Dome Cap Rock

Subject Group: Field Studies

Spec. Pub. Type: Special Volume

Pub. Year: 1926

Author(s): Marcus I. Goldman

Abstract:

Two kinds of cap rock are differentiated: the gypsum anhydrite-cap and the calcite cap. The gypsum is derived from the anhydrite by hydration and is characteristic of the upper part of the cap, where it contains much calcite and sulphur. The deeper, less altered part of the anhydrite cap shows parallel banding, which may be the result of diffusion, and breccia fragments of a parallel-banded, finer-grained anhydrite, which give evidence of sedimentary origin. Therefore, although no detrital minerals have been found in specimens of anhydrite cap, this cap is believed to be of sedimentary origin, brought up by an intrusive salt plug from depth. Possible explanations of the presence or absence of anhydrite caps on salt domes are offered. The calcite cap is the product of repl cement and penetration by calcite of the sedimentary beds adjacent to the gypsum-anhydrite cap and probably of the upper part of the gypsum-anhydrite cap itself. The sulphur in cap rock is characteristically associated with this calcite. The calcite and sulphur are probably the result of reduction of the outer parts of the anhydrite cap by hydrocarbons from adjacent beds. Constituents of minor importance are sulphides, carbonates of an early generation, barite, celestite, bipyramidal quartz crystals, and inclusions of sandstone in anhydrite.

Pay-Per-View Purchase Options

The article is available through a document delivery service. Explain these Purchase Options.

Watermarked PDF Document: $14
Open PDF Document: $24