File:Elephant Rock (Aztec Sandstone, Upper Triassic to Lower Jurassic; Valley of Fire, Nevada, USA) 7 (49673491776).jpg

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Differentially weathered sandstones in the Mesozoic of Nevada, USA.

The Aztec Sandstone is a widespread quartzose sandstone lithofacies in the lower Mesozoic of America's Southwest. It is Late Triassic to Early Jurassic in age and equivalent to the Navajo Sandstone, the Nugget Sandstone, and the Glen Canyon Sandstone (I wish they'd have one name only). The Aztec/Navajo/Nugget/Glen Canyon is an ancient eolian sand dune deposit. Vast "seas" of wind-blown sand dunes are called "ergs". The Sahara Desert in northern Africa is a modern example.

This photo shows the Aztec Sandstone at Valley of Fire in southeastern Nevada. The reddish color is from hematite (Fe2O3, iron oxide), which is natural "rust". Hematitic siliciclastic sedimentary rocks (sandstones, siltstones, shale) are called "redbeds". They first appear in the upper Paleoproterozoic stratigraphic record, about 1.8 billion years ago. This corresponds to times when Earth's atmosphere starting accumulating significant levels of free oxygen gas (O2). Earth's earliest air lacked free oxygen.
Date Taken on 6 July 2010, 11:14
Source Elephant Rock (Aztec Sandstone, Upper Triassic to Lower Jurassic; Valley of Fire, Nevada, USA) 7
Author James St. John

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This image was originally posted to Flickr by James St. John at https://flickr.com/photos/47445767@N05/49673491776. It was reviewed on 14 April 2020 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0.

14 April 2020

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current18:12, 14 April 2020Thumbnail for version as of 18:12, 14 April 20202,000 × 2,500 (3.5 MB)Poldavia (talk | contribs)Transferred from Flickr via #flickr2commons

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