GEOLOGIC MAPPING IN TEXAS

Recent geologic maps within two priority corridors for mapping will be presented. The North-Central to South-Central Texas population/transportation corridor contains areas undergoing population increase, rapid urban/suburban development, and industrial growth, which cause increased demands on groundwater and earth resources. Geologic maps within this corridor provide basic geologic framework data to aid in managing Earth and water resources, planning land use, identifying aquifer recharge areas, identifying potential Earth/mineral resources, and recognizing areas having stratigraphic units and associated soils prone to foundation problems. New maps south and north of the Dallas−Fort Worth metropolitan area display Quaternary deposits and Cretaceous units of limestone, argillaceous limestone, marl, shale, and sandstone, as well as quarry/pit and landfill areas. Within the Texas Gulf of Mexico coastal plain corridor, new geologic maps address needs for planning and management of land use and erosion issues, evaluating historical changes of coastal depositional environments, permitting activities related to resource development, and educating the public. A new map of the Nueces River−Delta−Bay complex depicts the Nueces Delta within the Nueces River valley, 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 the current shoreline; (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. Texas Bureau of Economic Geology mapping is supported by the STATEMAP program and the economic resources and hazards components of the STARR program.