Colorado Plateau 2005

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Switchbacks above the Redwall limestone (just visible at center left) climb up through Pennsylvanian to Permian units, the Supai Group, Hermit shale (280 Ma), and Coconino sandstone (275 Ma, cliffs at upper right), formed from cross-bedded dunes in a great Permian desert.

All images copyright © 2016 F.W. Vollmer and may not be used without permission.