Abstract

On the northeast edge of the Wichita Mountain Uplift, northwest of Loco, Oklahoma, is a depositional syncline with Pennsylvanian sediments ranging in age from Atoka through Virgilian. This depositional syncline was named the Harrisburg Trough by Harlton (1956a). Sedimentary onlap relationships within the Harrisburg Trough suggest that it formed as a topographic valley. Seismic evidence indicates that the valley may have had topographic relief of over 5,000 feet. Atokan drainage in part of the Harrisburg Trough was from southeast to northwest. Erosion of the highlands, comprised of Mississippian through Ordovician rocks, and located mainly to the south but also present to the north, provided the clastics deposited in the Trough.

The compression that probably caused the uplifted source areas continued through Virgilian time and folded the northeast flank of the Harrisburg Trough into the Northwest Velma and West Velma anticlinal hydrocarbon traps. In the future, hydrocarbons will probably be found in stratigraphic traps in Upper Dornick Hills sands that pinchout or onlap the flanks of the Trough.