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Great Unconformity Nevada outcrop

View on map:36.198547°N 115.008611°W

Comments

The Great Unconformity here is the contact between the dipping rocks of the Tapeats sandstone (525 million years old) and the Vishnu schist (1.7 billion years old).  The unconformity became famous after John Wesley Powell described it at the bottom of the Grand Canyon.  

Description


Great Unconformity

Of the many unconformities (gaps) observed in geological strata, the term Great Unconformity is applied to either the unconformity observed by James Hutton in 1787 at Siccar Point in Scotland, or that observed by John Wesley Powell in the Grand Canyon in 1869.[2] Both instances are exceptional examples of where the contacts between sedimentary strata and either sedimentary or crystalline strata of greatly different ages, origins, and structure represent periods of geologic time sufficiently long to raise great mountains and then erode them away.

References

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