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4,600 million years ago
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2500 million years ago
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2100 million years ago
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1900 million years ago
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1850 million years ago
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Orogeny (mountain building) Trans-Hudson Orogen
Earth changes from an anoxygenic environment to an oxygenic environment Martin Sandstone is deposited with Stromatolites (mounds created by blue-green algae) 1800 million years ago -
1700 million years ago
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1300 million years ago
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SK covered by the epicontinental Sauk Sea, hard shelled invertebrates including Trilobites 544 million years ago
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Also the Paleozoic Era and the Cambrian Period
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478 million years ago
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470 million years ago
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Later to become a trap for oil deposits 390 million years ago
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385 million years ago
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355 million years ago
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Also the Triassic Period
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248 million years ago
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245 million years ago
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220 million years ago
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213 million years ago
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100 million years ago
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75 million years ago
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70 million years ago
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66 million years ago
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65 million years ago
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Also the Tertiary Period and the Paleocene Epoch
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50 million years ago
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.05 million years ago
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2 million years ago
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.02 million years ago
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Also the Pleistocene Epoch
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.01 million years ago
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