SYNDEPOSITIONAL TECTONISM IN THE BLACK WARRIOR FORELAND BASIN (USA) RECORDED BY LATE MISSISSIPPIAN PALEOSEISMITES

The Black Warrior foreland basin, located at the juncture between the Ouachita and Appalachian thrust belts, records Late Mississippian through Early Pennsylvanian deposition and deformation that is important for deciphering spatial and temporal relationships between the two orogenic systems. We report the identification of paleoseismites from the northern Black Warrior foreland basin, within the Upper Mississippian Pride Mountain Formation. Subvertical, planar clastic dikes are interpreted as paleoseismites based on a dominant NW-SE dike trend, regional Paleozoic stratigraphic relationships, and the proximity to the Lowndes-Pickens subsurface fault-bounded block. The stratigraphic-geographic position of paleoseismites indicates development near the Late Mississippian surface and above basement fault(s) in a tensional stress regime, where SV > SHmax > SHmin. This model links displacement along basement faults that are preferentially oriented perpendicular to the plate convergence direction. Steeply-dipping, subvertical displacement of basement fault(s) results in the ground surface directly above to become arched, generating a stress field that promotes the development of syndepositional clastic dikes, joints, and normal faults parallel to the basement offset. We suggest the NW-SE orientation of clastic dikes indicates paleoseismite development in response to Ouachita deformation; thus, relating basement faulting to the northeastward migration of the Ouachita forebulge. This study highlights the capability of paleoseismites to interpret feedbacks between deformation and deposition in far-field foreland regions and the spatial-temporal evolution of thrust-belt systems.