Deep linear lake basins in West Texas originated by "cap rock" breaching along Pleistocene pluvial streams, but large shallow circular lake basins were caused mainly by "cap rock" breaching due to solution and leaching in blowouts. Large pluvial lake basins and associated playas oriented normal to ancient prevailing winds developed by end-current erosion during wet periods, but the small post-Wisconsin lake basins which now pockmark the plains, as well as the present playas of the larger pluvial basins, developed by wind deflation mainly during the arid Altithermal period 6,500 to 5,000 years B.P. Isolated examples of small basins formed by meteorite impact, animals, infiltration, and active sand dunes also exist. Small basins formed by differential subsidence and piping and roofing are unknown but may occur. Radiocarbon dates, sedimentation rates, and paleoclimatic studies indicate the basins have received little fill since the last pluvial period. Beneath thin Recent playa surface deposits is a thin zone of Wisconsin Tahoka Clay resting on a variable thickness of pre-Tahoka (pre-Wisconsin?) lacustrine strata. The large pluvial lake basins antedate approximately 27,000-year-old sediments, and the present playas postdate approximately 17,000-year-old strata.