The Cincinnati Arch: a stationary peripheral bulge during the Late Ordovician

Shallow-water features, including peritidal carbonate complexes, tidally influenced shoal-water facies, biostromes, and coincident subaerial unconformities on the peritidal complexes were restricted to the Cincinnati Arch during the Late Ordovician Taconic Orogeny. Persistence of these features along the Cincinnati Arch indicate that this area experienced decreased subsidence relative to surrounding areas, forming the peripheral bulge within the Taconic foreland basin. These shallow-water features are surrounded on all sides by deeper water, shallow subtidal to deep subtidal facies. The Jessamine and Nashville Domes were prominent topographic highs on the arch and were the locus of shallow-water deposition and subaerial erosion, but many of these shallow-water features also occur in the subsurface between the two domes. The shallow-water features and unconformities on the Cincinnati Arch occur in a narrow band repeatedly throughout the Late Ordovician. The width of these features is much too narrow to have formed solely by flexure of the lithosphere and their persistent formation in the same location indicates they did not form as a viscoelastic response to orogenesis. Rather the boundary between the Grenville Front and the Eastern Granite-Rhyolite Province acted as a focusing mechanism for the orogenic load stresses to the east, producing a relatively stationary peripheral bulge. A temporal and spatial change in the stratigraphy and subsidence on the Nashville and Jessamine Domes during the Edenian probably records a northward shift of loading, possibly sedimentary loading, during the Taconic Orogeny.