Downwarped and penecontemporaneously faulted beds of late Quaternary terrigenous sediment are well exposed in southeastern Briscoe County, Texas. Deformation probably was caused by subsidence of the Permian subcrop owing to dissolution of bedded salt at depth. Fluvial sands and gravels and lacustrine clays fill a subsidence basin, producing a locally thickened Quaternary section. A well-developed paleosol above lacustrine deposits was tilted and laterally truncated prior to modern eolian deposition at the site.
Active, recently active, and inactive subsidence features are common in the western Rolling Plains of Texas. Most of these features are small, karstic sinkholes up to 330 ft (100 m) in diameter and subsidence basins a few miles long. Gustavson and others (1982) investigated more than 400 of these features (dolines) in Hall and Briscoe Counties, Texas. These structures formed and are forming as a result of dissolution of Upper Permian (Ochoan and Guadalupian) evaporites, particularly halite, at depths of 650 to 1,000 ft (200 to 300 m) (Gustavson and others, 1982; McGookey and others, in press).
A similar pattern of karstic subsidence produced features of comparable size throughout late Pleistocene and Holocene time. During this interval, subsidence may have been more widespread than it is today because of the wetter climate and presumably greater rates of infiltration and transmissibility of ground water in the late Pleistocene (Carr and McGookey, in press). The moist climate of the late Pleistocene turned sinkholes and subsidence basins into pluvial ponds and lakes, the largest of which probably also received phreatic discharge. Limnic and lacustrine deposits occupy a stratigraphically consistent position in the Quaternary section of the western Rolling Plains. At one site, these deposits are more than 30 ft (9.1 m) thick and show evidence of structurally enhanced deposition.Bureau of Economic Geolog
