File:Interbedded metagraywacke-slate (Lake Vermilion Formation, Neoarchean, 2.695-2.722 Ga; Rt. 169 roadcut between Tower and Peyla, Minnesota, USA) 5 (20963580034).jpg

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Turbidites (interbedded metagraywacke and slate) in the Precambrian of Minnesota, USA.

Whitish-gray layers = metagraywacke Dark gray layers = slate

The 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, and soft-sediment deformation.

The gently folded layers are the result of pre-lithification soft-sediment deformation.

Stratigraphy: Lake Vermilion Formation, Neoarchean, 2.695-2.722 Ga

Locality: Pike Bay Drive East Outcrop - roadcut on the southern side of Rt. 169, immediately east of the eastern Rt. 169-Pike Bay Drive intersection, between the towns of Tower and Peyla, north-central St. Louis County, Minnesota, USA (47° 47’ 50.21” North, 92° 19’ 55.96” West)
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Source Interbedded metagraywacke-slate (Lake Vermilion Formation, Neoarchean, 2.695-2.722 Ga; Rt. 169 roadcut between Tower and Peyla, Minnesota, USA) 5
Author James St. John

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This image was originally posted to Flickr by James St. John at https://flickr.com/photos/47445767@N05/20963580034 (archive). It was reviewed on 5 December 2019 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0.

5 December 2019

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current05:48, 5 December 2019Thumbnail for version as of 05:48, 5 December 20194,000 × 3,000 (4.07 MB)Ser Amantio di Nicolao (talk | contribs)Transferred from Flickr via #flickr2commons

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