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The Gangplank
About 16 miles west of Cheyenne on I-80 |
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| The granite rocks to the west are more than a billion years old (Pre-Cambrian in age). The sedimentary rocks to the east are some 10 million years old (Late Miocene in age). After the mountains were elevated, some 20,000 feet of rocks were eroded from their crest. Later the younger sedimentary rocks were deposited against the flank of the range.
The time between the formation of the granite to the west and the deposition of the onlapping sediments to the east is measured in terms of more than ten hundred million years. You are now standing on the gangplank. |
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