| 11. | These rocks are from 414 mya in the Silurian period.
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| 12. | This thick sedimentary deposition continued into the Silurian period ( 444-416 million years old ).
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| 13. | The other one third of the rocks in Montour County are from the Silurian Period.
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| 14. | Casey is underlaid by rocks from the Silurian period.
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| 15. | Illinoisan trilobites diversity and abundance suffered further losses after the end of the Silurian Period.
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| 16. | First appearing in the Silurian period, millipedes are some of the oldest known land animals.
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| 17. | The Blue Ridge Mountains began forming during the Silurian Period over 400 million years ago.
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| 18. | The extinctions occurred approximately and mark the boundary between the Ordovician and the following Silurian Period.
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| 19. | The Silurian period, occurring 439 million years ago, has been well preserved nearby, in Wenlock Edge.
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| 20. | The sedimentary rocks in Montour County are from either the Devonian Period or the Silurian Period.
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