In cooperation with the U.S. Army

**Geologic Framework and Hydrogeologic   Features of the Glen Rose Limestone, Camp Bullis Training Site, Bexar County,   Texas**

By Allan K. Clark

U.S. Geological Survey  Water-Resources Investigations Report 03–4081

----

Document Accessibility: Adobe Systems Incorporated has information about PDFs   and the visually impaired. This information provides tools to help make PDF   files accessible. These tools convert Adobe PDF documents into HTML or ASCII   text, which then can be read by a number of common screen-reading programs that   synthesize text as audible speech. In addition, an accessible version of Acrobat   Reader 5.0 for Windows (English only), which contains support for screen readers,   is available. These tools and the accessible reader may be obtained free from   Adobe at http://access.adobe.com/.

pdf (14.3 MB)

plate (24" X 27") (1.55 MB)

----

**Contents**

Abstract 

Introduction 

Methods of Investigation 

Acknowledgments 

Geologic Framework 

General 

Stratigraphy 

Hydrogeologic Features of the Glen Rose Limestone 

General 

Upper Member 

Interval A 

Interval B 

Interval C 

Interval D 

Interval E 

Lower Member 

Summary 

References 

**Plate**

| 1.   | Map showing hydrogeologic subdivisions of the Edwards and       Trinity aquifers that crop out; and generalized stratigraphic section, Camp       Bullis Training Site, Bexar County, Texas |
|-----------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

**Figure**

| 1.   | Map showing location of Camp Bullis Training Site, Bexar County,       Texas |
|-----------|------------------------------------------------------------------------------|

**Table**

| 1.   | Summary of the lithologic and hydrogeologic properties of       the hydrogeologic subdivisions of the Glen Rose Limestone and associated       units that crop out, Camp Bullis Training Site, Bexar County, Texas |
|-----------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

----

**Abstract**

The Glen Rose Limestone crops out over most of the Camp Bullis Training Site   in northern Bexar County, Texas, where it consists of upper and lower members   and composes the upper zone and the upper part of the middle zone of the Trinity   aquifer. Uncharacteristically permeable in northern Bexar County, the Glen Rose   Limestone can provide avenues for recharge to and potential contamination of   the downgradient Edwards aquifer, which occupies the southeastern corner of   Camp Bullis.

The upper member of the Glen Rose Limestone characteristically is thin-bedded   and composed mostly of soft limestone and marl, and the lower Glen Rose typically   is composed mostly of relatively massive, fossiliferous limestone. The upper   member, about 410 to 450 feet thick at Camp Bullis, was divided in this study   into five hydrogeologic subdivisions, A through E (youngest to oldest).

The approximately 120-foot-thick Interval A has an abundance of caves, which   is indicative of its generally well developed fracture, channel, and cavern   porosity that in places provides appreciable permeability. The 120- to 150-foot-thick   Interval B is similar to Interval A but with less cave development and considerably   less permeability. The 10- to 20-foot-thick Interval C, a layer of partly to   mostly dissolved soluble carbonate minerals, is characterized by breccia porosity,   boxwork permeability, and collapse structures that typically divert ground water   laterally to discharge at land surface. The 135- to 180-foot-thick Interval   D generally has low porosity and little permeability with some local exceptions,   most notably the caprinid biostrome just below the top of the interval, which   appears to be permeable by virtue of excellent moldic, vug, fracture, and cavern   porosity. The 10- to 20-foot-thick Interval E, a layer of partly to mostly dissolved   evaporites similar to Interval C, has similar hydrogeologic properties and a   tendency to divert ground water laterally.

----