sandstone - teaching hand specimen of the Navajo Sandstone, a fine-grained orange-pink aeolian sandstone
The Navajo Sandstone makes up the cross-bedded cliffs at Zion National Park in Utah. Locally it is poorly to moderately well cemented with silica cement. These specimens are moderately cemented and will stand up to student examination, though grains of sand can be rubbed off.
Sand grains in the Navajo are entirely frosted quartz dune sand, as the depositional environment of this sand was an immense inland sand sea or erg on the western edge of the supercontinent of Pangea. The erg covered much of what is now Utah and parts of Colorado, Wyoming, New Mexico and Arizona. The grains essentially sandblasted each other as they were blown by the wind. These are large enough that with a 10x hand lens, a student can see the frosted surface, a characteristic of this sandstone.
The Navajo was deposited during the Jurassic. Detrital zircon geochronology indicates that the Navajo erg received some of its sediments from the Appalachians via a continent-spanning Mississippi-scale river system. Near Hurricane, Utah this sandstone is 2,400 feet thick.
The sand grains in these specimens are larger than those of a silt and will feel like fine sand to a student. It would be instructive to compare this sandstone with one is larger grained, with one that is cemented with calcium carbonate, and with different colored sandstones, as sandstone has great variety and a student should not see only one example.
Swallows build red nests under the overhang of the cliff where these specimens were collected from fallen blocks. The mud they use is stained by the same iron oxide that coats the grains of quartz in this sandstone.
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