GEOLOGY OF THE BARTON 7.5–MINUTE QUADRANGLE IN NORTHWEST ALABAMA AND TECTONIC INFLUENCES DURING THE LATE PALEOZOIC OROGENESIS

The Barton 7.5–minute quadrangle in northwest Alabama contains surficial exposures of the upper Mississippian Tuscumbia Limestone, Pride Mountain Formation, Hartselle Sandstone, and Bangor Limestone. The Tuscumbia Limestone contains bioclastic, cherty limestone that correlates to a period of low clastic influx during shallow basin conditions. The overlying shales, sandstones, and limestones of the Pride Mountain Formation represent the initiation of clastic sedimentation in the Black Warrior basin and preserves evidence of ancient seismic activity in the form of paleoseismites. The overlying Hartselle Sandstone, a barrier island complex composed of very fine to medium grained, white to tan, cross bedded sandstone is significant for the soft sediment deformation in the form of convolute bedding and slumps. The overlying dark gray to black micritic Bangor Limestone represents restricted basin conditions with decreased clastic sediment and increased accumulation of organic material. Upper Mississippian stratum is unconformably overlain by the unconsolidated or poorly consolidated iron-rich conglomerates and sandstones of the Cretaceous Tuscaloosa Group.

The paleoseismites within the Pride Mountain Formation are significant to understanding basement faulting during the Late Paleozoic. The provenance of sediment within the Hartselle Sandstone along with soft sediment deformations within the bedding may offer insight into the basin dynamics and/or active faults during early orogenesis. To supplement geologic mapping, we present U-Pb apatite and rutile data to assess models for the routing of clastic sediment into the Black Warrior basin, including a (1) continental drainage system (similar to the modern Mississippi River), and (2) locally sourced, orogenic system (similar to the Brahmaputra River drainage in and from the Himalaya Mountains).

Keywords: Hartselle Sandstone, Pride Mountain Formation, provenance, paleoseismites, Black Warrior Basin