File:Pleistocene terrace alluvium gravel atop Lower Jurassic Navajo Sandstone (north of Bootlegger Canyon, Utah, USA) 8.jpg

English: The reddish brown bedrock consists of 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.

The gravel atop the Navajo is Pleistocene-aged terrace alluvium (= unit "Qat" and "Qat6" on geologic maps of the area). This description is from Doelling et al. (1994): "Terrace alluvium -- Rounded, moderately sorted gravel (cobbles and pebbles) transported into the area by the Colorado River and deposited at several levels. Contains lenses of finer sand and silt, some of which contain flour gold and magnetite." This description is from Doelling et al. (2002): "Alluvial-terrace deposits (Pleistocene) - Moderately sorted, poorly stratified gravel in a calcareous sandy matrix; contain a variety of locally derived and exotic clasts . . . ; preserved as isolated remnants along major drainages; . . . Qat6 gravels are between 260 to 280 feet (70-85 meters) above the present stream channels; . . . ; as much as 60 feet (18 meters) thick.

Bedrock stratigraphy: Navajo Sandstone, Glen Canyon Group, Lower Jurassic

Locality: along Corona Arch Trail, north of Bootlegger Canyon & east of the Colorado River, west of the town of Moab, eastern Utah, USA

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References cited: Doelling, H.H., W.A. Yonkee & J.S. Hand. 1994. Geologic map of the Gold Bar Canyon Quadrangle, Grand County, Utah. Utah Geological Survey Map 155.

Doelling, H.H., M.L. Ross & W.E. Mulvey. 2002. Geologic map of the Moab 7.5' Quadrangle, Grand County, Utah. Utah Geological Survey Map 181.