Fault with fault breccia in interbedded metagraywacke-slate (Lake Vermilion Formation, Neoarchean, 2.695-2.722 Ga; Pike River Bridge outcrop, just north of Peyla, Minnesota, USA) 12 : 無料・フリー素材/写真
Fault with fault breccia in interbedded metagraywacke-slate (Lake Vermilion Formation, Neoarchean, 2.695-2.722 Ga; Pike River Bridge outcrop, just north of Peyla, Minnesota, USA) 12 / 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 | Faulted turbidites (interbedded metagraywacke and slate) in the Precambrian of Minnesota, USA.Whitish-gray layers = metagraywackeDark gray layers = slateThe Lake Vermilion Formation is a Precambrian stratigraphic unit in northeastern Minnesota, USA. It consists of low-grade metamorphosed volcaniclastic sedimentary rocks that were deposited in a moderately deep water marine environment.The outcrop shown above is a Pleistocene-glaciated knob of Lake Vermilion Formation turbidites, which consist of interbedded graywackes ("dirty sandstones") and shales - these have since been metamorphosed to metagraywackes and slates. Turbidites are deposits laid down by turbidity currents - underwater sediment slides. Such slides commonly occur in continental slope settings. Turbidity current deposits typically accumulate in the continental rise, at the base of the slope. Turbidites consist principally of interbedded coarse-grained and fine-grained siliciclastic sedimentary rocks that show graded bedding, climbing ripple cross-stratification, flame structures, flute casts, and soft-sediment deformation.The feature in the center of the photo is a fault zone, which has noticeably offset the layers. This fault contains broken and pulverized and sheared fragments of the host rocks, resulting in a thin zone of fault breccia.Stratigraphy: Lake Vermilion Formation, Neoarchean, 2.695-2.722 GaLocality: Pike River Bridge Outcrop - glaciated low outcrop on the western side of County Road 77, immediately north of bridge over the Pike River, just north of the town of Peyla, north-central St. Louis County, Minnesota, USA (47° 47’ 30.89” North, 92° 22’ 07.68” West) |
| 撮影日 | 2015-06-10 14:13:00 |
| 撮影者 | James St. John |
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