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Geologic Framework and Hydrostratigraphy of the Edwards and Trinity Aquifers Within Parts of Bandera and Kendall Counties, Texas

Scientific Investigations Map 3518
Prepared in cooperation with the Edwards Aquifer Authority
By: , , and 
https://doi.org/10.3133/sim3518

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  • Documents:
  • Data Release: USGS data release - Geospatial dataset for the geologic framework and hydrostratigraphy of the Edwards and Trinity aquifers within parts of Bandera and Kendall Counties, Texas, at 1:24,000
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Abstract

The karstic Edwards and Trinity aquifers are classified as major sources of water in south-central Texas by the Texas Water Development Board. During 2019–23 the U.S. Geological Survey, in cooperation with the Edwards Aquifer Authority, mapped and described the geology and hydrostratigraphy of the rocks composing the Edwards and Trinity aquifers within parts of Bandera and Kendall Counties from field observations of the surficial expressions of the rocks. The thicknesses of the mapped lithostratigraphic and hydrostratigraphic units were also estimated from field observations in the study area.

The Cretaceous rocks in the study area are part of the Trinity Group and Edwards Group. The groups, formations, and members are composed primarily of layers of marls, shales, and limestones. The limestones are composed of mudstone through grainstone, framestone and boundstone, dolomite, and argillaceous and evaporitic rocks.

The principal structural feature in the study area is the Balcones fault zone. The Balcones fault zone is the result of late Oligocene and early Miocene extensional faulting and fracturing that was a result of the eastern Edwards Plateau uplift. In the Balcones fault zone, most of the faults in the study area are high-angle to vertical, en echelon, normal faults that are predominantly downthrown to the southeast.

Hydrostratigraphically, the rocks exposed in the study area are those that contain the Edwards aquifer, the upper zone of the Trinity aquifer, and the middle zone of the Trinity aquifer. Descriptions of the hydrostratigraphic units, thicknesses, hydrologic function, porosity types, and field identification and observations are provided, including those for the informal Bandera and Love Creek hydrostratigraphic units of the Edwards aquifer, which were identified through the mapping for this study.

Suggested Citation

Clark, A.K., Morris, R.R., and Lamberts, A.P., 2024, Geologic framework and hydrostratigraphy of the Edwards and Trinity aquifers within parts of Bandera and Kendall Counties, Texas: U.S. Geological Survey Scientific Investigations Map 3518, 1 sheet, scale 1:24,000, 11-p. pamphlet, https://doi.org/10.3133/sim3518.

ISSN: 2329-132X (online)

Study Area

Table of Contents

  • Acknowledgments
  • Abstract
  • Introduction
  • Methods of Investigation
  • Geologic Framework
  • Hydrostratigraphy
  • Summary
  • References Cited
Publication type Report
Publication Subtype USGS Numbered Series
Title Geologic framework and hydrostratigraphy of the Edwards and Trinity aquifers within parts of Bandera and Kendall Counties, Texas
Series title Scientific Investigations Map
Series number 3518
DOI 10.3133/sim3518
Year Published 2024
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Oklahoma-Texas Water Science Center
Description Pamphlet: vi, 11 p., 1 Sheet: 49.01 x 39.83 inches; Data Release
Country United States
State Texas
County Bandera County, Kendall County
Other Geospatial Edwards and Trinity Aquifers
Online Only (Y/N) Y
Google Analytic Metrics Metrics page
Additional publication details