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Geologic stratigraphic column of strata exposed in and near the Grand Canyon. The term Great Unconformity is frequently applied to the unconformity observed by John Wesley Powell in the Grand Canyon in 1869. [1] It is an exceptional example of relatively young sedimentary rock strata overlying much older sedimentary or crystalline strata.
The resulting Grand Canyon Supergroup of sedimentary units is composed of nine varied geologic formations that were laid down from 1.2 billion and 740 million years ago in this sea. [11] Good exposures of the supergroup can be seen in eastern Grand Canyon in the Inner Gorge and from Desert View, Lipan Point and Moran point. [12] [note 1]
In the Grand Canyon, the Bright Angel Shale is generally about 110 to 150 m (360 to 490 ft) thick. In the western Grand Canyon, the Bright Angel Shale is over 140 m (460 ft) thick and decrease eastward in thickness to only about 82 m (269 ft) at Toroweap in the central canyon. It is 100 m (330 ft) thick in Bright Angel Canyon.
In the Grand Canyon, the Tapeats Sandstone is a medium- to coarse-grained, thin-bedded, cliff-forming conglomeratic sandstone that weathers to a tan or reddish-brown. Its thickness varies from very thin or absent where deposited over prominent paleotopographic highs, as much as to 90 m (300 ft) high.
On February 26, 2019, the Grand Canyon National Park commemorated 100 years since its designation as a national park. [15] The Grand Canyon had been part of the National Park Service's Intermountain Region until 2018. [citation needed] Today, the Grand Canyon is a part of Region 8, also known as the Lower Colorado Basin. [16]
The Mesoproterozoic formations in the Grand Canyon are overlain by the 850 million year old, Neoproterozoic Chuar Group and Sixtymile Formation sedimentary rocks. The Great Unconformity is a famous gap in the stratigraphic record of the Grand Canyon of 900 million years between Proterozoic granitic rocks and Cambrian marine sediments. For the ...
In 1901 the Grand Canyon Railway was opened from Williams, Arizona, to the South Rim, and the development of formal tourist facilities, especially at Grand Canyon Village, increased dramatically. The Fred Harvey Company developed many facilities at the Grand Canyon, including the luxury El Tovar Hotel on the South Rim in 1905 and Phantom Ranch ...
Within the central Grand Canyon, Unkar strata occur in small, rotated, downfaulted blocks or slivers where they commonly are only partially exposed. Within this center part of the Grand Canyon, the Unkar Group is incomplete because pre-Tonto Group erosion has removed strata above the level of the middle part of the Dox Formation.