Abstract

The U.S. Geological Survey and the Ohio Geological Survey recently compiled aero-magnetic anomaly maps and revised gravity anomaly data for crustal studies of Ohio. Updated structural and lithologic maps of the Precambrian basement surface provide additional constraints to limit interpretational ambiguities of the geopotential anomaly data. The combined modeling of five east-west gravity and magnetic anomaly profiles supports a generalized crustal model for Ohio involving a lower zone of intermediate composition, a more felsic and relatively homogeneous middle zone, and an upper zone consisting of intrusive and extrusive igneous rock in the western third of the state and medium-grade Grenville metamorphic rocks to the east. Modeling of the geopotential field anomalies indicates the presence of large, dense lower crustal bodies in western and south-central Ohio that may be related to a paleo-rift system. Large, possibly anorthositic masses in southern Ohio, post-tectonic granitization in northwestern Ohio, and a volcanic source for igneous rocks in southwestern Ohio may also be interpreted from the combined anomaly analysis.

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