Abstract: Early Pennsylvanian Wrenching Along the Red River-Matador Arch: Formation of a Pull-Apart Basin, Depocenter for Atokan to Lower Des Moines (Bend) Clastics, Cottle County, Texas
William C. Stephens Jr., Robert D. Gunn
Early Pennsylvanian wrenching along the Red River-Matador Arch (Tectonic Zone) created a braided series of en echelon faults and folds with associated pop-up structures and pull-apart basins. Local extension, or overstepping, in Southeast Cottle County, Texas, has produced the deepest pull-apart basin along the arch with over 10,000^prime of structural relief. The emerging Wichita-Amarillo Uplift, to the north, provided an abundant sediment source, which prograded rapidly southward as an alluvial fan-braided river complex. Exposure of basement rocks and lower Paleozoic sediments along the Red River-Matador Arch, also contributed to the basin fill.
Syntectonic sedimentation led to the accumulation of over 6000^prime of Bend (Atoka-lower Des Moines) sediments within the basin. Deposition was dominated initially by alluvial fan to fluvial siliciclastics. As basin subsidence was further amplified by sediment loading, accommodation exceeded sedimentation capturing a large segment of the southward prograding Wichita-Amarillo derived clastic wedge. Encroachment of the late Atoka to lower Des Moines epeiric sea promoted further evolution of depositional environments to fan deltas, marine dominated clastics and, later, localized carbonate development. Type III kerogen rich organic shales produced abundant gas prone source rocks. The extreme depth of the basin combined with the local geothermal gradient provided for significant hydrocarb n generation.
By early 1988 new well control helped revise previous stratigraphic correlation demonstrating a rapidly expanding lower Des Moines to Atokan section. The drilling of the Gunn Oil Company-Brothers #1 to a total depth of 10,301^prime in the Mississippian Chappel Limestone, encountered 2025^prime of Bend sediments, with 279^prime of gross Bend Conglomerate (162^prime of net pay). The Brothers #1 was potentialled on 11/19/89 with a CAOF of 6.0 MMCFD and filed as the field discovery for the Broken Bone (Bend Conglomerate) field.
AAPG Search and Discovery Article #90960©1995 AAPG Southwest Section Meeting, Dallas, Texas