STATEMAP PROGRAM GEOLOGIC MAPPING IN TEXAS

Recent geologic mapping in Texas has focused on work to support improved geologic map database development for the Texas Gulf of Mexico coast/coastal plain region, the central Texas corridor west of Austin, and local Texas areas having sand resources. Examples of new maps, scales 1:24,000 and 1:50,000 will be presented. Maps of Texas coast/coastal plain areas address geologic-framework needs for planning and management of land use, evaluating historical changes of coastal depositional environments, addressing erosion issues, permitting activities related to resource development, and educating the public. These maps illustrate Pleistocene and Holocene deposits of fluvial-deltaic and barrier systems. The central Texas corridor west of Austin has been experiencing rapid development and population increases for a number of years. New maps provide a basic geologic framework to aid in managing water and earth resources and planning land use. Geology of this corridor consists of about 1,200 ft of Lower Cretaceous shelf and shore-zone deposits including Sycamore conglomerate, sandstone, and mudstone, Hammett shale and minor sandstone, Cow Creek limestone and sandy limestone, Hensel sandstone, mudstone, sandy to silty limestone, and dolomitic limestone, Glen Rose limestone, dolomite, dolomitic limestone, and argillaceous limestone, Walnut limestone, argillaceous limestone, Walnut limestone, argillaceous limestone, marl, and lesser dolomitic limestone, and Edwards limestone and dolomite. The area also contains Quaternary terrace deposits of the Colorado River (parts of Lake Travis), Pedernales River, Blanco River, and several prominent creeks. Recent mapping of sand resource areas focused on the Cambrian Hickory Sandstone in central Texas and the Eocene Carrizo Sandstone of south-central Texas. This mapping helps address the need to evaluate industrial-sand/hydraulic-fracturing-sand resources to support unconventional oil and gas exploration and production.