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The Cambrian Bright Angel Shale is the middle member of the 3-member Tonto Group. It is about thick at its maximum.〔Chronic, H (1983) ''Roadside Geology of Arizona.'' The Mountaineers Books, Seattle, Washington. (softcover, ISBN 978-0-87842-147-3)〕 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.〔Anonymous (2006c) (''Bright Angel Shale'' ), (Stratigraphy of the Parks of the Colorado Plateau ). U.S. Geological Survey, Reston, Virginia.〕 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.〔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.〕 ==Geologic sequence== The units of the Tonto Group:〔 * (1)-Temple Butte Limestone, Devonian-(409-363 Ma), channel deposits upon Muav Limestone * Tonto Group (~544-505 Ma) * * 3-Muav Limestone * * 2-Bright Angel Shale * * 1-Tapeats Sandstone 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「Bright Angel Shale」の詳細全文を読む スポンサード リンク
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