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Karst Development within the Salado Creek Watershed, Williamson and Bell Counties, Central Texas

Abstract

Karst development in the Edwards Aquifer of Central Texas has been significantly studied in the San Antonio and Barton Spring segments; however, karst development remains poorly studied in the Northern Segment, where municipalities rely heavily on fluvial resources. Current studies within the Salado Creek Watershed in northern Williamson and southern Bell counties, shows a dominant control of planar surfaces, including fractures and bedding planes, on cavernous porosity. Karst exhibits preferential dissolution along stratigraphic horizons that dip gently towards the Balcones Fault Zone, including highly porous vuggy zones and brecciated zones. The Northern Segment of the Edwards Aquifer consists of the Comanche Peak, Edwards, and Georgetown formations. The Edwards Limestone contains massive to thick-bedded limestone, dolomitic limestone, dolomite, and minor argillaceous limestone with mudstone, wackestone, and packstone, textures. Caves are dominantly oriented along fractures near-perpendicular to the strike of the Balcones Fault Zone with lateral widening, including vadose and phreatic morphologies.

Current data analyses indicate epigene karst development within the Salado Creek Watershed is tied to the geomorphic evolution of Salado Creek and primary local system discharge through Salado Springs. Surface denudation coupled with stream incision has partially partitioned shallow epigene karst system within the watershed. Spring geochemistry is being utilized to better understand the connections between the groundwater and the underlying geologic formations for development of karst groundwater models for the Northern Segment.