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Generalized Geologic Map of the Conterminous United States
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  The North American Tapestry of Time and Terrain

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  Legend and Rock Ages
 

Devonian Rocks - 410 to 360 million years ago

map of Devonian rocks

 

The fossil record of the Devonian is marked by an extinction that killed 40% of all marine life took place. The causes for this are uncertain, but possible factors may include glaciation, atmospheric changes or meteor impacts.

Devonian-aged rocks can be found in the regions around the Michigan Basin and the Finger Lakes and in the Appalachian Valley and Ridge Province.