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| The North American Tapestry of Time and Terrain | |||
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| Legend and Rock Ages | |||
Proterozoic Rocks - 2.5 billion to 540 million years ago |
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The Proterozoic was a time in which multicellular algae began to appear. The continents grew in size and oxygen began to build up in the atmosphere. Today, Proterozoic rocks are found in features like the Superior Upland, the Black Hills, the Llano Uplift, and the Adirondack Mountains. The Proterozoic has been divided here into the following (youngest
to oldest): |
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