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The Grand Canyon Supergroup is a Mesoproterozoic to Neoproterozoic sequence of sedimentary strata, mostly exposed in the eastern Grand Canyon of Arizona. This group is composed of the Unkar Group, Nankoweap Formation, Chuar Group and the Sixtymile Formation, which overlie Vishnu Basement Rocks. Several notable landmarks of the Grand Canyon, such as the "Isis Temple and Cheops Pyramid" and the "Apollo Temple," are surface manifestations of the Grand Canyon Supergroup. ==Geology== The Grand Canyon Supergroup uncomformably overlies the Vishnu Basement Rocks, but were never subjected to metamorphism. The units of the Supergroup were faulted and then tilted from 10 to 15 degrees.〔Timmons, M, KE Karlstrom, and C Dehler (1998) (''Grand Canyon Supergroup Six Unconformities Make One Great Unconformity A Record of Supercontinent Assembly and Disassembly'' ). (Boatman's Quarterly Review. vol. 12, no. 1 ), pp. 29–32. online: accessed April 2014〕 A section of the Unkar Group members is visible north of Grand Canyon Village, on the South Rim; specifically at the intersection of the Bright Angel Fault and the Grandview–Phantom Fault (which cuts through Phantom Creek), on the North Rim (at the north side of Granite Gorge). The majority of the Grand Canyon Supergroup geologic members are found in the south and south-southwest stretch of the Colorado River as it issues from Marble Canyon; traverses the southeast perimeter of the Kaibab Plateau; and flows northeasterly, entering Granite Gorge and regions of the Vishnu Basement Rocks. Here, the river leaves the last of the Unkar Group lower-unit members behind. Other sections of the Unkar Group reappear downstream, due to the general faulting of the Grand Canyon. ; The units of the Grand Canyon Supergroup〔Lucchitta; 2001; figure #9: ''Geologic section of the Grand Canyon showing its stratigraphy''; p. 64; accessed .〕 (1250 Ma to 700 Ma): * 4--Sixtymile Formation (ends at ~700 Ma) * 3--Chuar Group * * ()-Kwagunt Formation * * ()-Galeros Formation * 2--Nankoweap Formation * 1--Unkar Group * * (5)--Cardenas Basalt, youngest, Meso-Proterozoic 1070 ± 70 million years * * (4)--Dox Formation * * (3)--Shinumo Quartzite * * (2B)--Diabase sills-(4 sills, 25 ft thickness max; sources of Cardenas Basalt) * * (2)--Hakatai Shale * * (1)--Bass Formation, (begins at ~1250 Ma) 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Grand Canyon Supergroup」の詳細全文を読む スポンサード リンク
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