Paleodepositional Facies Lower Cretaceous Cow Creek Member Texas Hill Country

By

WILSON, WILLIAM FEATHERGAIL

Strata Geological Services, Inc., Bandera, TX

The Lower Cretaceous Cow Creek Member of the Pearsall Formation serves as a common aquifer for several Texas Hill Country counties. This paper addresses the paleodepositional aspects and facies architecture of the unit as it relates to water availability across the counties of Bandera, Bexar, Comal, Kendall and Kerr Counties, Texas.

The Cow Creek has previously been depicted as a relatively uniform facies of high energy carbonates. Instead, it is a complex array of facies architecture that ranges through a number of lithologies and paleoenvironments of deposition. Facies include high and low energy carbonates, sand, silt, coal and microdolomite. Some of these units are quite widespread. The major facies are believed to be partially controlled by underlying structural geologic elements. These same elements control roughly north-south channels that were cut into the Cow Creek, which may be syndepositional in certain areas.

The mapping of the Cow Creek is part of a long term project to define water availability of the Lower Cretaceous aquifers across the Texas Hill Country. This paper presents the first map associated with the long term goals of the project. Subsequent maps will be published of each discrete aquifer. Both stereo and petrographic microscopes were utilized to generate the data and interpretations.