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Geologic Map
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Generalized Geologic Map of the Conterminous United States
North America Shaded Relief


  The North American Tapestry of Time and Terrain

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Pre-Pleistocene River System

  Close-up of
 Teays River geology

Traces of an old east-west drainage system, buried by glacial deposits not shown on the map, are conspicuous across northern Ohio and Indiana. Presence of the pre-Pleistocene Teays River is revealed as a sinuous, branching pattern of Ordovician rocks (dark violet) surrounded by overlying Silurian strata (pale violet). The old river channel was abandoned when its course was diverted southward to the Ohio River drainage by the movements of early Pleistocene ice and the emplacement of glacial deposits, probably about 2 million years ago.