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Shelf-Interior Carbonate Grainstone Shoals: Lower Cretaceous Pearsall Formation, South Texas

By
Robert G. Loucks
Robert G. Loucks
ARCO Oil and Gas Company, Exploration and Production Research, Geological Research Group, Plano, Texas 75221
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Don G. Bebout
Don G. Bebout
Bureau of Economic Geology, University of Texas at Austin, Austin, Texas 78712
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Published:
January 01, 1984

Abstract

Shoal-water carbonate complexes developed over a low-relief structure (Pearsall arch) on the Lower Cretaceous shelf of South Texas in the Sligo, Pearsall, and Glen Rose Formations. One of these complexes in the Pearsall Formation, the Cow Creek Limestone, was penetrated and cored in the Tenneco No. 1 Sirianni well, Frio County. The Sirianni well encountered the thickest part of the Cow Creek complex.

Three shoaling-upward cycles were encountered. The lower cycle contains echinoid-mollusk wackestones and packstones, deposited under low-energy subtidal conditions, overlain by echinoid-mollusk grainstones, deposited in an intertidal shoal environment. The second cycle is similar to the lower cycle except that ooid grainstones are well developed in the upper part of the grainstone unit. The upper cycle comprises another wackestone to ooid-skeletal grainstone upward shoaling sequence which is capped by boundstones and grainstones deposited in a patch-reef complex.

Porosity is facies controlled in that 95% occurs in the grainstones. Facies maps, therefore, serve also as porosity-distribution maps.

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Contents

SEPM Core Workshop Notes

Carbonate Sands-A Core Workshop

Paul M. Harris
Paul M. Harris
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SEPM Society for Sedimentary Geology
Volume
5
ISBN electronic:
9781565762602
Publication date:
January 01, 1984

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