Stratigraphic, geomorphic and structural controls of the Edwards Aquifer, Texas, U.S.A.

Eugene S. Simoson
John Sharp

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The Edwards aquifer is a narrow band of Cretaceous carbonate rocks on the peri­phery of the Gulf Coastal Plain. The aquifer's great productivity is caused by early Cretaceous and late Cenozoic karstification, enhanced along fractures and Miocene-age faults. Primary flow is subparallel to sttike for the most part, but is directed subparallel to dip at the aquifer's western and northern extremities. Recharge is predominantly by losing streams and .natural discharge is primarily to springs along incised major streams. Water quality is controlled by aquifer stratigraphy, stmcture, and lithology, and by a variety ofhydrogeochemical processes: cross-fonnational flow, mixing with saline fonnation waters, and rock-water interactions within the aquifer. The aquifer is both confined and unconfined. Proper development and utilization of this important aqllifer requires an understanding of the aquifer's structural, geomorphic, geochemical, and stratigraphic evolution.