| 词条 | Bright Angel Shale |
| 释义 |
| image =Grand Canyon-Mather point.jpg | imagesize = 285px | caption = Muav Limestone-(dk or lt gray, brown, or orange-red subcliff at base of Redwall Limestone cliff) and Bright Angel Shale (greenish slope-former), resting on Tapeats Sandstone (short, dp brown vertical cliff) (Tapeats forms the "Tonto Platform"), inner canyon, Granite Gorge. (The 3 units–Muav, Bright Angel, and Tapeats, are easily seen below the red-stained Redwall Limestone (550 ft thick)) | period = Cambrian | age = Middle Cambrian[1][2] | type = Geological formation | prilithology = micaceous siltstone and shale | otherlithology = sandstone and glauconitic sandstone | namedfor = Bright Angel Canyon, Bright Angel quadrangle, Coconino Co., Arizona[3] | namedby = Noble (1914)[3] | region = northern Arizona, southeast California, southern Nevada, and southcentral Utah |country = United States of America | coordinates = | unitof = Tonto Group | subunits = | overlies = Tapeats Sandstone | underlies = Muav Limestone | thickness = {{convert|500|ft|m|sp=us}} at its maximum | extent = | area = | map = | map_caption = }} The Cambrian Bright Angel Shale is the middle member of the 3-member Tonto Group. It is about {{convert|500|ft|m|0}} thick at its maximum.[4] It is a nonresistant slope-forming unit. The Bright Angel Shale consists of green and purple-red, siltstone and shale which is interbedded with red-brown to brown sandstone that is similar in lithology to the underlying Tapeats.[5] The Bright Angel Shale underlies and interfingers with Muav Limestone. The Bright Angel Shale is located in the lower elevations of the Grand Canyon, Arizona.[6] Geologic sequenceThe units of the Tonto Group:[4]
See also
References1. ^Rose, E (2006) "Nonmarine aspects of the Cambrian Tonto Group of the Grand Canyon, USA, and broader implications." Palaeoworld. 15:223–241. 2. ^Rose, E (2011) Modification of the nomenclature and a revised deposition model for the Cambrian Tonto Group of the Grand Canyon, Arizona. in JS Hollingsworth, FA Sundberg, and JR Foster, eds., pp 77-98, Cambrian Stratigraphy and Paleontology of Northern Arizona and Southern Nevada: Museum of Northern Arizona Bulletin 67, 321 p. 3. ^1 Noble, LF (1914) The Shinumo quadrangle, Grand Canyon district, Arizona. Bulletin no. 549, US Geological Survey, Reston, Virginia. 4. ^1 Chronic, H (1983) Roadside Geology of Arizona. The Mountaineers Books, Seattle, Washington. (softcover, {{ISBN|978-0-87842-147-3}}) 5. ^Anonymous (2006c) Bright Angel Shale, Stratigraphy of the Parks of the Colorado Plateau. U.S. Geological Survey, Reston, Virginia. 6. ^Hampton, HM (1998) Geologic Map of the Grand Canyon in the Vicinity of the South Rim Visitor Center. in Kamilli, RJ, and SM Richard, eds., Geologic Highway Map of Arizona, Arizona Geological Society and Arizona Geological Survey, 1 sheet, scale 1:62,500. Popular Publications
External links{{external links|date=September 2013}}
7 : Shale formations of the United States|Natural history of the Grand Canyon|Geologic formations of Arizona|Geologic formations of Nevada|Cambrian Arizona|Cambrian Nevada|Cambrian System of North America |
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