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The Cambrian Muav Limestone is the upper geologic unit 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) p. 179.〕 It is a resistant cliff-forming unit. The Muav consists of dark to light-gray, brown, and orange red limestone with dolomite and calcareous mudstone.〔Anonymous (2006d) (''Muav Limestone'' ), (Stratigraphy of the Parks of the Colorado Plateau ). U.S. Geological Survey, Reston, Virginia.〕 The Muav is overlain in some areas by the Devonian Temple Butte Limestone, but the major unit above are the vertical cliffs of Mississippian Redwall Limestone. The Muav 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.〕 The Muav is in-part younger than, and in-part grades into, the Bright Angel Shale which is less erosion resistant and is categorized as a slope-forming unit. The Muav is about 350 feet thick in the east and reaches about 600 feet thick in the western part of its exposure area in the Grand Canyon.〔 The two units lie above the erosion-resistant cliff-forming Tapeats Sandstone. In the eastern canyon, the Tapeats creates the horizontal Tonto Platform. In west Grand Canyon, the north-south Toroweap Fault is the west perimeter of the Tonto Platform, and west Grand Canyon is dominated by the erosion resistant unit of the Esplanade Sandstone. The Tonto Trail is a mostly horizontal trail on the south side of Granite Gorge, on the platform. The Tonto Group units were deposited on an ancient erosion surface (angular unconformity) on the Vishnu Basement Rocks. The Vishnu sequence has a dip of about 45 degrees. As this unconformity represents about 1,000 million years (1.0 billion years) of non–deposition, tectonic activity and erosion on the Vishnu Basement Rocks is called the Great Unconformity. Beyond the Grand Canyon area the Muav occurs in southern Utah, southern Nevada and southern California. In the California occurrence it is known as the Muav Marble.〔 ==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「Muav Limestone」の詳細全文を読む スポンサード リンク
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