--> Abstract: Environmental Geology of Urban Growth Areas within the Edwards Aquifer and Balcones Fault Zone, South-Central Texas, by E. Collins; #90932 (1998).

Datapages, Inc.Print this page

Abstract: Environmental Geology of Urban Growth Areas within the Edwards Aquifer and Balcones Fault Zone, South-Central Texas

COLLINS, EDWARD
Bureau of Economic Geology, The University of Texas at Austin, Austin, TX

New geologic maps of areas within the Edwards aquifer that are undergoing increased urban development, population growth, and exploitation of natural resources provide basic geologic information necessary for management of water and land resources, land-use planning, and construction practices Results of 1:24,000-scale mapping in the urban growth corridors of Austin-Georgetown, New Braunfels-San Antonio, and west San Antonio are presented. The Balcones Fault Zone, which is the main structural control on the Edwards aquifer and recharge zone, crosses the map areas and mostly consists of multiple fault blocks bound by a long series of southeast-dipping, en echelon normal faults. Cretaceous limestone, marl, and shale crop out along the fault zone and represent >2,000 ft of shelf and shelf-margin deposition. Basic geologic knowledge concerning faults and the limestone and dolomitic limestone that contain the Edwards aquifer is required to manage issues such as ground-water flow and aquifer response to pumpage and recharge. The outcrop belt of Edwards, Comanche Peak, and part of the Walnut make up the recharge zone of the aquifer. Some large faults within the aquifer may act as barriers to groundwater flow, whereas other faults and joints form local and regional groundwater conduits. Karst features such as sinkholes and solution cavities may be key recharge features. Geologic data for the area are also necessary for land-use decisions such as locating landfills and other waste disposal sites, planning construction projects, and designing foundations. For example, Del Rio clay often causes construction problems due to swelling and shrinking, slumping can occur in clay-rich units, and harder limestone units may require different techniques to excavate than do softer units.

AAPG Search and Discovery Article #90932©1998 GCAGS/GCS-SEPM Meeting, Corpus Christi, Texas