Deliberately MISreading again? The implication is that the last Glaciation and post-glaciation COVERED what had been exposed in an earlier age.
The latest thinking on the creation of the Grand Canyon involves the breach of Upper Mid-Continent glacial dams and the resulting release of fantastic quantities of water - this may have happened several times over thousands of years.
No, but it did create a large underground aquifer that would show up millions of years later as a brightly colored blob on a chart, getting modern day neanderthals all excited.
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