Far–field tectonic controls on deposition in the Appalachian Basin – A case study of Late Cambrian–Late Ordovician strata in Morrow County, Ohio

Far–field tectonics can often be overlooked when studying orogens, particularly when much of the deformation occurs near the loading loci. As stresses are propagated further from the loading into the craton, whether compressional, extensional, or shear, faults and fractures within the basement often act as pathways for stress transmission, traveling along these pre-existing planes of weakness, or creating new. The Appalachian Basin in the eastern United States is a classic foreland basin example that showcases far-field tectonic influence on deposition and structure. This study characterizes the structural architecture of the basement along the western Appalachian Basin margin by analyzing well log data from 2,662 wells to create structure, isopach, trend surface, and residual maps of Late Cambrian through Upper Ordovician strata (Knox through Black River). Fourteen lineaments interpreted as faults were delineated, creating two series of horsts and grabens. The northeast–southwest faults are related to structures that formed during Keweenawan extension, and the northwest–southeast faults are related to structures that formed during the Grenville Orogeny. Both sets of faults stem from the Precambrian basement and are shown to have been reactivated during the Blountian Tectophase of the Taconian Orogeny (Black Riverian deposition), creating localized thinning and thinning adjacent to the lineaments. Furthermore, these faults appear to have undergone additional reactivation since the deposition of these strata in a transtensional regime to create the observed horst and graben structures. Overall, far–field tectonics plays an important role in understanding the geologic history of a basin.