TECTONIC EVOLUTION OF THE DEVONIAN ACADIAN FORELAND-BASIN SYSTEM, EASTERN UNITED STATES

Regional isopach maps of Devonian rocks from the northern Appalachian basin help define the tectonic history of the eastern United States during the Acadian Orogeny. During Early Devonian time, the northern Appalachian basin was the location of a slowly subsiding, shallow-marine seaway situated at the margin of the low-elevation Taconic highlands to the east. During the Middle Devonian, collision between the Avalonian arc-terrane along the eastern margin of North America resulted in orogenic uplift and crustal thickening across the pre-existing Taconic highlands and flexural partitioning of the Appalachian basin to the west. This partitioning segmented the basin into foredeep, forebulge, and back-bulge depozones of an integrated foreland-basin system. Continued collision-related shortening along the eastern margin during the Late Devonian, as well as depositional loading within the basin, resulted in the westward migration of the foreland-basin system depozones through time. By the end of Devonian time, the foredeep extended into eastern Ohio, with the forebulge crest running parallel to the structural trend of the modern-day Cincinnati Arch.