Data from five drainage basins in the Texas Panhandle and northeastern New Mexico characterize the recent history of regional drainage basin formation and landscape development around the margins of the Southern High Plains.

Sandstone in the Travis Peak (Hosston) Formation has been extensively modified by burial diagenesis. Permeability in much of the formation has been reduced to less than 0.1 md as a result of compaction, extensive precipitation of authigenic minerals, and minor pressure solution.

Deep brine aquifers of the Palo Duro Basin, Texas Panhandle, ranging in depth from about 1,000 to 3,000 m below land surface, are underpressured compared with the shallow Ogallala aquifer.

Changes in the position and stability of shorelines in the San Antonio Bay system (San Antonio, Espiritu Santo, and Mesquite Bays), Texas Gulf Coast, were documented using historical monitoring techniques.

Porous and permeable strata of the Deep-Basin Brine aquifer underlie bedded evaporites that are being considered as repositories for high-level nuclear waste isolation in the Palo Duro Basin, Texas Panhandle. Formation-water samples collected from four U.S.

Ground water that moves downward from aquifers in clastic rocks of the Triassic Dockum Group and Neogene Ogallala Formation dissolves bedded halite and anhydrite in the Upper Permian evaporite section along the perimeter of the Southern High Plains in the Texas Panhandle.

The Van Horn Mountains caldera is a small (~10-km2) igneous center in the Trans-Pecos volcanic province. The caldera formed 37 to 38 mya during eruption of the first of two ash-flow tuffs related to the caldera.

This folded transparent map is at the same scale as its corresponding Geologic Atlas of Texas (GAT) sheet and can be superimposed on it to compare gravity information with surface geology.