Natural arch developed in Jurassic sandstones in Utah, USA.
These are eolian sandstones of the Navajo Sandstone, a thick, Mesozoic-aged unit representing ancient sand dune deposits. The Navajo is a prominent cliff-forming unit in much of western America. The coloration is from hematite (Fe2O3 - iron oxide). Laterally-equivalent units are known by other names, but are all the same deposit: Glen Canyon Sandstone, Nugget Sandstone, and Aztec Sandstone.
Rock arches are rare features - they form by differential weathering and erosion of many different types of rocks, but often sandstone. If a creek or river passes underneath, it is a natural bridge. If no creek or river is present, it is a natural arch. Along lakeshores and ocean coastlines, they are called lake arches and sea arches. Very small erosional openings in rocks are called windows.
This example is Bowtie Arch, a pothole-type natural arch. It is not in Arches National Park, which is located northeast of here.
Stratigraphy: Navajo Sandstone, Glen Canyon Group, Lower Jurassic
Locality: Bowtie Arch, north of Bootlegger Canyon & east of the Colorado River, west of the town of Moab, eastern Utah, USA (38° 34' 50.03" North latitude, 109° 37' 18.04" West longitude)
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