Chuar Group
| 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 | Arizona, Utah |
| Country | United States |
| Type section | |
| Named for | Chuar Canyon |
| Named by | Walcott (1894) and Noble (1910, 1914) |
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.