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Geologic Map
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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
Rock Types
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  Legend and Rock Ages

Pennsylvanian Rocks - 325 to 286 million years ago

map of Pennsylvanian rocks

  The Pennsylvanian is the upper, or younger, part of the Carboniferous. This section is rich in coal, which is the reason this part of the time scale is called the Carboniferous. As plates moved over the globe, the areas now known as Europe, Africa, and North America collided. This collision formed the Appalachian Valley and Ridge Province that run through the eastern continent. This mountain-building event extended far west, creating the Ouachitas in the southern U.S., and is even visible in Oklahoma's Wichita Mountains.

Other Pennsylvanian-aged rocks can be found in the Michigan Basin and in the recessional moraines around the Great Lakes.