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| This view is looking west from the Tipoff along the South Kaibab Trail toward the Colorado River in the Inner Gorge. The Bright Angel Trail is visible along the south bank of the river. Precambrian-age crystalline Vishnu Basement Rocks (schist and granitic dikes of Early Proterozoic age). The name Vishnu Basement Rocks is used to cover an assemblage of rock types exposed in the Inner Gorge. The names Vishnu Schist, Brahma Schist, Rama Schist, and Zoroaster Granite are perhaps best known to the public, but researchers have applied many other names and subdivisions and classifications to the Precambrian-age crystalline rocks exposed in the canyon. This view also shows the Precambrian-age sedimentary rocks of the Unkar Group which include include, from bottom to top, the Bass Formation (mostly limestone) Hakatai Shale (red shale), and Shinumo Quartzite (dense sandstone and quartzite). The Greatest Angular Unconformity is between the Vishnu Basement Rocks and the Unkar Group. The Great Unconformity is between the top of the Unkar Group and the base of the Cambrian-age Tapeats Sandstone. The Tapeats sandstone it is visible capping the bluff on the right side of the image. Throughout this area the rocks are locally offset by several faults (Beus, 1990; Billingsley, 2000; Billingsley and others 1997). |
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