Abstract:
The Choctaw Fault and Ross Creek Fault are the leading-edge thrusts of the Ouachita fold-thrust belt and form the southern boundary of the Arkoma foreland basin in Oklahoma and Arkansas, respectively. Strain partitioning between the fold-thrust belt and the foreland basin is accommodated by the Wilburton Triangle Zone in the footwall of the Choctaw Fault of Oklahoma; however, few studies document the geometry of Ouachita-Arkoma transition zone in Arkansas. This study uses depth-converted 2-D seismic reflection profiles and well log data to clarify the subsurface structure and establish the presence or lack of triangle zone elements within the accommodation zone between the Choctaw Fault and Ross Creek Fault in north-central Scott County, western Arkansas. Structural interpretation of three depth-converted 2-D seismic profiles shows a triangle zone containing the surficial tip-out of the Choctaw Fault in the footwall of the Ross Creek Fault. This triangle zone is called the Waldron Triangle Zone after nearby Waldron, Arkansas, and is composed of three stacked wedges that share a roof thrust, the north-dipping lower Atokan Decollement, which meets a floor thrust, the south-dipping Stanley Decollement, at a tip line below the Poteau Syncline. Knowledge of accommodation zone structure predicts that the Waldron Triangle Zone dies out west of the seismic data into Oklahoma and coincides with the formation of the laterally equivalent Wilburton Triangle Zone.
