PRECAMBRIAN STRUCTURE UNDERLYING PALEOZOIC STRUCTURE FROM 2-D SEISMIC INTERPRETATION, NORTHERN APPALACHIAN BASIN, OHIO

Large scale arches and small-scale folds have been mapped and described by Ohio geologists since the 19^th century. Most of the shallow folds were mapped in the Pennsylvanian-aged strata of eastern Ohio. Early workers noted that the axial strike of mapped folds in Ohio were not parallel to the folds mapped in the Appalachian fold and thrust belt and interpreted a different origin for folds in Ohio. Lineaments derived from recent structure contour mapping of Silurian- through Devonian-aged strata in eastern Ohio parallel and underlie many of the folds mapped by earlier workers, indicating an underlying fabric controlling the structural orientations observed in eastern Ohio. With insufficient density of Ordovician and deeper well penetrations, seismic data is needed to determine the origin of Paleozoic structures.

Interpretation of publicly available seismic data of eastern Ohio was limited to the Consortium for Continental Reflection Profiling line OH-2, indicated that the Cambridge Arch is a result of reactivation of basement faults; however, the smaller-scale folds are not seen on the relatively coarse line. The Ohio Geological Survey gained restricted access to three speculative seismic surveys from Evans Geophysical Inc. (EGI). Line EGI-OH-05-11 extends from Holmes to Belmont Counties. The line crosses identified surface folds and subsurface lineaments in western Tuscarawas County. Basement reflector patterns beneath the upper-level folds and lineaments show basement structure is at the root of the structures through the stratigraphic section. In Harrison County, line EGI-OH-05-11 shows a complex basement structure underlying the surface-mapped Cadiz anticline. Line EGI-03-11 extends from Muskingum to Belmont Counties crossing the Cambridge Arch. Line EGI-03-11 shows that the Cambridge Arch is flanked to the east by down-to-the-east basement faults which create folds mapped higher in the Paleozoic section. Line EGI-OH-09-13 extends from Morgan to Washington Counties. The line crosses the Cambridge Arch, Parkersburg syncline, and Liberty Arch. The line shows the Cambridge Arch is also flanked to the east by a series of basement faults which propagate into the Paleozoic section. The seismic data indicates that structure in the Precambrian basement influenced Paleozoic structure.