Mancos Shale over Frontier Sandstone (Upper Cretaceous; western Dinosaur National Monument, Utah, USA) 9 : 無料・フリー素材/写真
Mancos Shale over Frontier Sandstone (Upper Cretaceous; western Dinosaur National Monument, Utah, USA) 9 / James St. John
| ライセンス | クリエイティブ・コモンズ 表示 2.1 |
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| 説明 | Tectonically tilted shales and sandstones in the Cretaceous of Utah, USA.The mottled gray rocks at center-right in the picture are part of the Mancos Shale, a thick, widespread, dark-colored, deep-water marine shale unit of Late Cretaceous age in western America. Outcrops occur in Colorado, Utah, Arizona, and New Mexico. The formation ranges from sparsely fossiliferous shales to fossiliferous calcareous shales. The Mancos Shale is not resistant to weathering and frequently forms distinctive, grayish-colored badlands. "Badlands" refers to a landscape unsuitable for farming. Such terrains are complexly dissected (eroded), have steep slopes, relatively soft rocks (usually shale), little to no soil, and little to no vegetation. Good examples of badlands topography are the Book Cliffs of eastern Utah, the Chinle Formation badlands of Arizona, the White River badlands of South Dakota (Badlands National Park), and the Little Missouri badlands of North Dakota (Roosevelt National Park).The rocks at center-left in the photo are the Frontier Sandstone (Frontier Formation). It underlies the Mancos Shale - both units have been tectonically tilted and are dipping to the right. The Frontier Sandstone is also a marine unit, but is a coarse-grained, shallow water to shoreline deposit.Cretaceous-aged marine deposits are widespread in western North America - they represent sedimentation during a sea level highstand. During the Cretaceous, global sea level was so high that an ocean (the Western Interior Seaway) separated eastern and western North America. The Cretaceous transgression was a result of relatively rapid seafloor spreading rates (tectonic divergence) in some oceans basins. This lifted considerable portions of the seafloor, which raised global sea levels.Stratigraphy: Mancos Shale over Frontier Sandstone, Upper CretaceousLocality: western Dinosaur National Monument, northern Uintah County, northeastern Utah, USA------------Geology partly synthesized from:Frazier & Schwimmer (1987) - Regional Stratigraphy of North America. 719 pp.------------See info. at:en.wikipedia.org/wiki/Dinosaur_National_Monument |
| 撮影日 | 2012-06-08 15:06:11 |
| 撮影者 | James St. John |
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