GEOSPATIAL ANALYSIS OF FEATURES ON THE DALQUEST DESERT RESEARCH STATION, BIG BEND, TEXAS

The MSU Texas Dalquest Desert Research Station (DDRS) encapsulates 3,000 acres to the northeast of Big Bend Ranch State Park in southwestern Texas. It is largely underlain by Eocene and Oligocene volcanogenic and lacustrine deposits that are modified by Basin and Range taphrogeny. These are mapped as six formations: starting with the oldest, the Devil’s Graveyard Fm, the Solitario Conglomerate, the Terneros Creek Rhyolite, the Mitchell Mesa Fm, the Tascotal Fm, and the Rawls Fm. Faulting includes the Tascotal Mesa Fault (TMF), one of a handful of regional east-striking faults, exhibiting appreciable right-lateral offset with a south wall downthrown by a yet-to-be documented throw.

This study is evaluating TMF kinematics through careful, decimeter-scale digital mapping documented within a GIS environment. To provide a more robust control, we completed a high-resolution GNSS field survey of the basal Rawls, a distinct marker linked to TMF movement. The basal Rawls is a white to purple tuff overlain by a basalt flow marked by calcite veining and vugs in most exposures, the elevation and position of which has been modified by the TMF.

This survey was done using the Trimble TDC 150 Handheld Data Collector with integrated GNSS receiver. The data was then uploaded into ArcGIS and a map was created of the area. Of the 58 survey points, 45 of them include the positions of the basal Rawls lava (tuff/basalt contact) on each side of the TMF. These were along the base of Tascotal Mesa, between the domes of Teneros Creek Rhyolite, and above Alamo Springs on Alamo de Cesario Creek. The rest of the survey points locate key geologic landmarks, such as the “Purple Bench” in the lower Devil’s Graveyard, and infrastructure landmarks visible on satellite imagery (main gate, building features, roads, and boundary markers). The points had an average horizontal accuracy of 0.55 m and a vertical accuracy of 2.06 m. Mapping uses the WGS 1984 geodetic datum. Features are underlain by the World Imagery base map, with one-meter resolution satellite imagery. The WorldElevation3D/Terrain3D topography layer provides 3D aspect.