GEOLOGIC MAPPING OF THE TEXAS GULF OF MEXICO COASTAL PLAIN

Recent 1:24,000-scale geologic maps address needs for evaluating historical changes of coastal depositional environments, planning and management of land use, erosion issues, and habitat conversion, permitting activities related to resource development, and educating the public. New maps of the Aransas and Mission Rivers and deltas at Copano Bay display Modern to Holocene fluvial and delta units, Pleistocene upland deposits of the coastal plain, and Pleistocene barrier deposits. Three topographic scarps having relief of 1.5 to 5 ft were also mapped using high-resolution airborne lidar data. Two possible origins are faulting and relic shorelines reflecting marine retreat, although study of the scarps is ongoing. A new map of the lower Nueces River valley depicts the Nueces delta where it has prograded into upper Nueces Bay during the Late Holocene. This map illustrates a variety of geologic elements, including (a) shorelines of the Nueces Delta during 1882, 1930, 1959, and 2012; (b) nine delta lobes representing different deposition packages; (c) clay dunes, levee deposits, young fans and terraces at the mouths of small drainages that flow into the Nueces Valley, and young terrace deposits developed along the margin of Nueces Valley; and (d) Holocene to upper Pleistocene Deweyville deposits and upper Pleistocene Beaumont Formation deposits. Mapping is supported by the STATEMAP program and the Bureau of Economic Geology hazards and mapping/economic resources components of the STARR program.