Mancos Shale badlands (Upper Cretaceous; near the town of Grand Junction, Colorado, USA) 9 : 無料・フリー素材/写真
Mancos Shale badlands (Upper Cretaceous; near the town of Grand Junction, Colorado, 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 |
|---|---|
| 説明 | Sandstones over shales in the Cretaceous of Colorado, USA.The Mancos Shale is 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 has an intertonguing relationship with the Dakota Sandstone - many sections have coarse-grained siliciclastic intervals broadly interbedded with fine-grained siliciclastics.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.The Mancos Shale is a non-weathering resistant unit and frequently forms distinctive, mottled grayish 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).In the above photo, the slopes of the Mancos Shale are capped by erosion-resistant sandstones of the Mesaverde Sandstone.Stratigraphy: lower Mesaverde Sandstone over upper Mancos Shale, Campanian Stage, Upper CretaceousLocality: view from Interstate 70 near the town of Grand Junction, Mesa County, far-western Colorado, USA------------Geology partly synthesized from:Frazier & Schwimmer (1987) - Regional Stratigraphy of North America. 719 pp. |
| 撮影日 | 2011-09-07 15:59:33 |
| 撮影者 | James St. John |
| タグ | |
| 撮影地 |