| Chuar Group | |
|---|---|
| Stratigraphic range: | |
| Type | Geological formation |
| Unit of | Grand Canyon Supergroup |
| Sub-units | Kwagunt Formation Galeros Formation |
| Underlies | Sixtymile Formation and, as part of the Great Unconformity, the Tapeats Sandstone |
| Overlies | Nankoweap Formation |
| Thickness | 1,600 m (5,200 ft) at maximum |
| Lithology | |
| Primary | mudstone |
| Other | dolomite and sandstone |
| Location | |
| Region | (eastern) Grand Canyon-(southwest) Colorado Plateau  Arizona-(north)  Utah-(southern) |
| Country |  United States |
| Type section | |
| Named for | Chuar Canyon[1] |
| Named by | Walcott (1894)[1] and Noble (1910, 1914)[2][3] |
The Neoproterozoic Chuar Group consists of 1,600 m (5,200 ft) of exceptionally well-preserved, unmetamorphosed sedimentary strata that is composed of about 85% mudrock. The Group is the approximate upper half of the Grand Canyon Supergroup, overlain by the thin, in comparison, Sixtymile Formation, the top member of the multi-membered Grand Canyon Supergroup. The outcrop of the Chuar Group strata is limited to exposures along the western bank of the Colorado River in a 150 km2 (58 sq mi) area of the eastern Grand Canyon, Arizona. The strata of the Chuar Group have been subdivided into the Galeros Formation (lower) and the Kwagunt Formation (upper) using the base of the prominent, thick sandstone unit.[4][5]
- ^ a b Walcott, CD (1894) Precambrian igneous rocks of the Unkar terrane, Grand Canyon of the Colorado. 14th Annual Report for 1892/3, part 2, pp. 492–519, United States Geological Survey, Reston, Virginia.
- ^ Noble, LF (1910) Contributions to the geology of the Grand Canyon, Arizona; the geology of the Shinumo area (continued). American Journal of Science. Series 4, vol. 29, pp. 497–528.
- ^ Noble, LF (1914) The Shinumo quadrangle, Grand Canyon district, Arizona. Bulletin no. 549, US Geological Survey, Reston, Virginia.
- ^ Ford, TD, and CM Dehler (2003) "Grand Canyon Supergroup: Nankoweap Formation, Chuar Group, and Sixtymile Formation." in: Beus, S.S., Morales, M., eds., pp. 49–72, Grand Canyon Geology. Oxford University Press, New York.
- ^ Dehler, CM, SM Porter, and JM Timmons (2012) "The Neoproterozoic Earth system revealed from the Chuar Group of Grand Canyon", in JM Timmons and KE Karlstrom, eds., pp. 49–72, Grand Canyon Geology: Two Billion Years of Earth's History. Special Paper no. 489, Geological Society of America, Boulder, Colorado.