sandstone - Coconino Sandstone - aeolian quartz arenite from northern Arizona - teaching hand specimen
The Permian age Coconino Sandstone unconformably overlies the Hermit Shale and unconformably underlies the Seligman Member of the Toroweap Formation, extending across northern and central Arizona. It is aeolian, a noncalcareous quartz arenite with frosted grains and large scale crossbedding.
A quartz arenite is the most mature sedimentary rock, with a composition over 90% quartz grains and almost everything else removed by weathering before deposition. The Navajo Sandstone, which forms the red cliffs of Zion National Park is also a crossbedded quartz arenite with frosted grains that became frosted by being blown against each other in an immense Jurassic dune field like the Great Sand Sea in western Egypt today.
These specimens were collected north of Ash Fork, Arizona. Ash Fork is the "Sandstone capital of the world," with quarries in the Coconino shipping slabs of this sandstone worldwide. Weathered, this sandstone is brown/maroon. With the weathered surface removed it is light tan to pink.
The first field photo shows one of the quarry stone yards at Ash Fork. The second photo shows weathered blocks of the Coconino.
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