This layer averages about 260 million years old and is composed of pure quartz sand, which are basically petrified sand dunes. Wedge-shaped cross bedding can be seen where traverse-type dunes have been petrified. The color of this layer ranges from white to cream colored. No skeletal fossils have yet to be found but numerous invertebrate tracks and fossilized burrows do exist.
 
Grand Canyon Rock Layers
 

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