Mudcracks in dolomicrite (Mill Knob Member, Slade Formation, Upper Mississippian; Rt. 1274-Rt. 801 outcrop, southwest of Morehead, Kentucky, USA) 5 : 無料・フリー素材/写真
Mudcracks in dolomicrite (Mill Knob Member, Slade Formation, Upper Mississippian; Rt. 1274-Rt. 801 outcrop, southwest of Morehead, Kentucky, USA) 5 / 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 | Mudcracked dolomicrite in the Mississippian of Kentucky, USA. (bedding plane view; geology hammer for scale)This is an outcrop of Upper Mississippian Slade Formation in Kentucky. The unit was formerly known as the Newman Limestone ("They always change the names to protect the innocent!"). Slade Formation limestones are shallow ocean deposits.These light-colored rocks are dolomicrites - fine-grained dolostones composed of mud-sized sediments. Dolostone is similar to limestone, but consists of dolomite (CaMg(CO3)2) instead of calcite (CaCO3). Dolostone is identified by bubbling in acid when powdered with a knife. Limestone bubbles in acid without being powdered.The irregularly polygonal structures on this bedding plane exposure are mudcracks. These are diagnostic sedimentary structures that indicate subaerial exposure of sediment surfaces, and are formed by alternating wet and dry conditions. They are much more common that raindrop imprints, which indicate the same environmental setting. Mudcracks are most likely to occur in fine-grained siliciclastic rocks, fine-grained carbonate sediments, and in some evaporitic successions. Mudcracks are distinctive and easy to identify, but they do vary in appearance. The cracks themselves vary in width, depth, and areal density. Mudcrack polygons also vary in size and shape.Stratigraphy: Mill Knob Member, Slade Formation, Upper MississippianLocality: roadcut next to the Route 1274-Route 801 intersection, southwest of the town of Morehead, Kentucky, USA. (vicinity of 38° 04’ 51.58” North latitude, 83° 25’ 21.64” West longitude) |
| 撮影日 | 2018-03-11 15:02:35 |
| 撮影者 | James St. John |
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