In Texas, the Lower Cretaceous was deposited on an extensive broad, flat platform which extended from the Stuart City shelf margin on the downdip or seaward side to the area of Abilene in North Texas on the updip or landward side (fig. 1). Shallow-water shelf carbonate deposition, which took place over an area of more than 160 thousand square miles, was influenced by three major structural elements-the more rapidly subsiding McKnight and North Texas/Tyler Basins and the more positive Llano uplift.

Ground-water resources in the Corpus Christi area-Nueces, San Patricio, Refugio, and Aransas Counties (fig. 1)-were investigated as part of a broader study of land and water resources of the four-county area (Kier and others, 1974a and 1974b; Kier and White, in preparation). Although surface water, primarily from Lake Corpus Christi on the Nueces River near Mathis, is the principal fresh water supply for the City of Corpus Christi and numerous other communities in the region (table 1), ground water is also a significant resource in the area.