About This Item

Share This Item

The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 69 (1985)

Issue: 2. (February)

First Page: 313

Last Page: 313

Title: Textural Evidence for Origin of Salt Dome Anhydrite Cap Rocks, Winnfield Dome, Louisiana: ABSTRACT

Author(s): Mark R. Ulrich, J. Richard Kyle, Peter E. Price

Article Type: Meeting abstract


Textures within anhydrite cap rock are products of repeated cycles of halite dissolution and residual anhydrite accretion at tops of salt stocks. Quarrying operations at Winnfield dome have exposed extensive portions of the anhydrite cap rock zone. This zone is composed primarily of unoriented, xenoblastic anhydrite crystals in laminae less than 1 mm to several centimeters thick. Laminations are defined by thin, dark sulfide accumulations and pressure solution of anhydrite. Deformed, banded anhydrite clasts are contained locally within laminae. Multiple-laminated, concave downward anhydrite mounds occur along some horizons. They may contain anhydrite breccia fragments or sulfides. Coarsely crystalline salt mounds, containing disseminated idioblastic anhydrite also occur a ong horizons. Mound morphologies vary from tall and thin to broad and squat; maximum dimensions range from less than 0.5 m to about 2.0 m. These moundlike structures are related spatially and genetically.

Moundlike structures are believed to form from salt spines along the salt-anhydrite contact. As the spine dissolves through several cycles of dissolution and accretion, a laminated anhydrite mound is preserved; if the spine becomes isolated from dissolution, then a salt inclusion is preserved. Anhydrite beds within the Louann Salt, deformed during diapirism, are preserved as deformed anhydrite clasts. Steeply dipping, bedded anhydrite zones within the salt stock may produce brecciated anhydrite mounds when incorporated into the cap rock. Sulfides record the movement of metalliferous fluids through the salt-anhydrite contact. Cores from other Gulf Coast domes indicate that these textures and interpreted processes are common.

End_of_Article - Last_Page 313------------

Copyright 1997 American Association of Petroleum Geologists