THE ANCESTRAL SALT FLAT GRABEN. ALTERNATIVE PALEOZOIC HISTORY OF THE SIERRA DIABLO AND APACHE MOUNTAIN AREA, TRANS-PECOS, WEST TEXAS

The presence of thick Powwow Conglomerates in the subsurface in the Van Horn area, the lack of siliciclastics in the Upper Guadalupian (Grayburg and Queen) of the Apache Mountains and the location of the Ochoan marine channel connecting the western Delaware Basin to the Permian Ocean can all be explained by the presence of an ancestral Salt Flat Graben. Evidence from exploration wells and outcrop data indicates that the faults bounding the Salt Flat to Lobo Valley Graben trend was periodically active during the Paleozoic and are not solely Basin and Range age structures.

The Sierra Diablo, Beach, Carrizo and Van Horn Mountains are postulated to have periodically been low relief highlands beginning in the Ordovician and continuing thru the Permian. These ranges formed the western boundary of the Lower Paleozoic Tobosa Basin. During the Permian, the presence of this highland impacted facies distribution. In the Lower Wolfcampian, large quantities of eroded Lower Paleozoic sediments were shed into the active potion of the graben system. During the Upper Wolfcampian, isolated blocks capped with carbonate banks within the Sierra Diablo, shed debris into the trough. These blocks also controlled the development of Leonardian age shelves in the Sierra Diablo Range. During the Guadalupian, the Sierra Diablo highlands deflected siliciclastics eastward into the Delaware Basin. During the Ochoan, the southern part of the graben system served as the western marine channel to the Permian ocean.

The recurrent activity of the graben system during the Paleozoic separated the Apache and Davis Mountains from the Sierra Diablo Platform. The presence of an Apache Platform, bounded on the east by the Hovey Channel and on the west by the Salt Flat graben system is supported by the data.