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The Late Mississippian-Early Pennsylvanian Surprise Canyon Formation is a conglomerate, sandstone, limestone〔''Geologic Map of the Grand Canyon in the Vicinity of the South Rim Visitor Center,'' based on: ''Geologic map of the eastern part of the Grand Canyon National Park, Arizona,'' P. W. Huntoon and others, (c. 1995, Grand Canyon Association), (from ''Geologic Highway Map of Arizona'', from Reynolds, c. 1988).〕〔''South Rim (geologic) Visitor Center Map'', Stratigraphy Chart.〕 and dark purple siltstone type formation, occurring as 'channel fill'.〔''South Rim (geologic) Visitor Center Map'', Stratigraphy Chart.〕 The Surprise Canyon Formation was deposited upon a mostly horizontal, much eroded Redwall Limestone surface, the Redwall originally deposited as marine-(oceanic) limestone, (400 to 700 ft thick); when the Surprise Canyon Formation was being deposited, the Redwall Limestone surface existed under karst topography conditions, in a "warm, and humid"〔Chronic, 1983. ''Roadside Geology of Arizona,'' c. 1983, Grand Canyon National Park, pp. 279-287, p. 283.〕 (paleo)-environment. The karst topography created "sinks, caves, and underground channels", and created "deep ravines and stream valleys developed as caverns collapsed".〔Chronic, 1983, p. 283.〕 Some valleys probably filled with ''" 'clayey red-orange soil' similar to that known in the Tropics today."''〔Chronic, 1983, p. 283.〕 Below the Redwall surface, solution-cavern deposits of the Surprise Canyon, have a Redwall Limestone geologic layer, now expressed above them. The Surprise Canyon Formation is found extensively in regions below Grand Canyon Village, Arizona, South Rim, regions northwest, north, and northeast. It is discontinuous, but is found in geologic sequences below the South Rim, and its various landforms, and also especially at the Inner Gorge in specific landforms that have cliffs, and upper surface platforms of the Redwall Limestone. Example landforms near Grand Canyon Village, are Pattie Butte-(Newton Butte), Tower of Set, (due west of Isis Temple), and Brahma Temple's southern Redwall Limestone points, Johnson and Sturdevant Points, due east of Isis Temple. Fossils of plant material, marine shells, where some fossils may have been 'derived fossils' from the Redwall Limestone, are found in the formation; also fossil logs, showing the erosion, or valley and canyon topographies and the erosional forces of the time period. Besides the easily recognized locations of the Surprise Canyon Formation on the Redwall Limestone platforms, it is found in more vertical sequences where the lowest Supai Group member, the Watahomigi Formation, major sub-unit 1 of 4, transitions, and sits upon the Surprise Canyon, upon the Redwall Limestone. As stated, the Surprise Canyon in the Grand Canyon Village region is discontinuous, but occurs in all sub-sections, further explaining a many-channeled paleo-surface of the eroding Redwall Limestone. The supplementing, and later hypothesis is that marine conditions, to the west of the proto-North American continent, had created an estuarine region, with accumulations of the continental erosion; with apparent uniform thicknesses of the Surprise Canyon, as opposed to highly variable thickness, near sea-level conditions, and probably lack of high terrains on the eroding Redwall surface, and all factors leading to the thin, discontinuous accumulations, but thin lenses, and regionally extensive in the estuary (sea level) region. The Redwall Limestone member itself is massive, and is very continuous, and is found as a base geologic unit for much of Grand Canyon; it also forms the walls of Marble Canyon in the northeast canyon, where the Colorado River makes its entrance, about 30-mi,〔Arizona Road & Recreation Atlas, Benchmark Maps, 2nd Edition, c. 1998, pp. 62-63.〕 north-northeast of the Grand Canyon Village region, South Rim. ==Surprise Canyon and Temple Butte Formations== In the central Grand Canyon, the Surprise Canyon and Temple Butte formations have equivalent thicknesses, averaging 75-150 ft. The major difference between the two is that the Devonian Temple Butte was deposited in the western Grand Canyon, and regions in Nevada, on the passive margin of the North American proto continent; the continental shelf was subsiding, and the Temple Butte reached a thickness of about in west Grand Canyon at the Grand Wash Cliffs, and even greater thicknesses ) in the Frenchman Mountain region of Nevada. Both the Temple Butte and Surprise Canyon Formations were deposited on erosional unconformities, on karst terrains of the Muav and Redwall limestones. The following is a chart of the Surprise Canyon Formation, Redwall Limestone, Temple Butte Formation, and other related geologic units across the Colorado Plateau:〔Blakey, Ranney, 2008. ''Ancient Landscapes of the Colorado Plateau'', Graphic: ''Columnar cross-sections of Paleozoic rocks showing the stratigraphic nomenclature and correlations used in this book,'' pg. XVIII.〕 File:Grand Canyon view.jpg|Dramatic Redwall Limestone cliffs, on ridgeline (cliffline) south, and part of the Tower of Set, East Granite Gorge (Inner Gorge, Grand Canyon) File:Tonto-trail.jpg|The Tower of Set on Inner Gorge-(east Granite Gorge).(View, from across Granite Gorge (south side, short Tapeats Sandstone cliffs visible at top of Gorge), from the Tonto Trail.) 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「Surprise Canyon Formation」の詳細全文を読む スポンサード リンク
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