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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
 

Permian Rocks - 286 to 248 million years ago

map of Permian rocks

 

The supercontinent of Pangaea was completed during the Permian period. The continent was so large that it reached from the north pole to the south pole. It was surrounded primarily by a huge ocean called the Panthalassa, with a smaller body of water, the Tethys, just to its east.

The Permian is perhaps most notable for the event that occurred at its end, a massive global extinction. This extinction severely affected marine invertebrates, wiping out most of their populations; it is believed to have killed more than 80% of life on the planet. The causes are uncertain, but it's believed that changes in sea level and anoxic (low oxygen) water conditions played a role.

Some Permian rocks can be found in western Texas, in the area of the Rio Grande Rift, and around the Grand Canyon.