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Oligocene |
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Time: |
36.6 to 23.7
mya |
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Duration: |
12.9 million years |
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There are
hundreds of small, thin coal deposits during this time period in western North America.
Their widespread occurrence suggests that intermittent swampy conditions existed
throughout the entire Oligocene (36.6 to 23.7 million years ago). These very young coals
are not commercial. |
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