BEDROCK GEOLOGIC MAPPING IN SELECTED AREAS OF OHIO AND ITS RELATIONSHIP TO SUBSURFACE GEOLOGY

ABSTRACT The Ohio Geological Survey has completed mapping the bedrock geology and bedrock topography of the state. Topography of the bedrock surface controls the distribution of bedrock units in the glaciated portions of Ohio. Paleovalleys on the bedrock surface in western and central Ohio have long, linear sections and northwest-southeast and northeast-southwest preferred orientations. Selected major valleys correspond to geologic structures in the subsurface. Some of these valleys correspond to the elongation and boundaries of some oil and gas fields, or to zones of limited oil and gas production. The northwest-southeast joint pattern in the surface bedrock is in part controlling the orientation of the buried valleys. The joint pattern itself is in part controlled by reactivation of deep-seated faults and structures originating from Precambrian rifting and mountain-building episodes. The location and orientation of buried valleys may be useful as a predictive tool in the search for subsurface geologic structures in glaciated portions of Ohio.