Planed-off cross-bedding (Dakota Sandstone, Lower Cretaceous; Dinosaur Ridge, Colorado, USA) 2 : 無料・フリー素材/写真
Planed-off cross-bedding (Dakota Sandstone, Lower Cretaceous; Dinosaur Ridge, Colorado, USA) 2 / 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 | Rippled sandstone in the Cretaceous of Colorado, USA.This outcrop is at Dinosaur Ridge, which is a section of the Dakota Hogback, a north-south trending ridge of eastward-dipping Mesozoic sedimentary rocks. Triassic, Jurassic, and Cretaceous rocks are present, tilted by the Laramide Orogeny during the Cenozoic.The exposure consists of structurally tilted beds of the Dakota Sandstone, a Lower Cretaceous succession of nearshore terrestrial to intertidal to shallow marine quartz sandstone deposits. Dinosaur tracks are common on some Dakota Sandstone bedding planes.The closely-spaced linear structures in the picture are crossbeds, seen in bedding plane view. Cross-bedding consists of tilted layers between horizontal layers. They form in a one-directional current. There are many named varieties, based on the specific geometries of the crossbeds (e.g., tabular cross-bedding, tangential cross-bedding, trough cross-bedding, hummocky cross-bedding, herringbone cross-bedding, etc.).Stratigraphy: Dakota Sandstone, Albian Stage, upper Lower CretaceousLocality: eastern side of Dinosaur Ridge, between Interstate 70 and the town of Morrison, west of Denver, north-central Colorado, USA |
| 撮影日 | 2007-11-01 16:16:48 |
| 撮影者 | James St. John |
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