File:Skolithos trace fossils in quartzose sandstone (Mazomanie Formation, Upper Cambrian; riverside cliff, western side of the St. Croix River, northeast of Lookout Point, Minnesota, USA) 8 (18379756133).jpg
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Skolithos trace fossils in quartzose sandstones in the Cambrian of Minnesota, USA. This outcrop consists of quartzose sandstones of the Mazomanie Formation, a shallow marine siliciclastic succession in the Upper Cambrian of the Upper Mississippi Valley, USA. Cross-bedding and Skolithos trace fossils are common here. Intraclastic sandstone horizons are also present. The brown-colored, linear structures shown above that are cutting across the sandstone's horizontal bedding and cross bedding are Skolithos trace fossils. Many shallow-water quartzose sandstones have these conspicuous, often long, usually vertical burrows. Geologists traditionally consider Skolithos to be a burrow of a filter-feeding vermiform organism in a shallow-water, high-energy lithofacies. Most Skolithos occurrences in the geologic record may be safely interpreted as such, but some demonstrably terrestrial examples constructed by other organisms have been discovered. The brownish-coloration of the burrows is due to iron oxide staining. Stratigraphy: Mazomanie Formation, upper Tunnel City Group (formerly the Franconia Sandstone), Sunwaptan Stage, Upper Cambrian, ~491-493 Ma Locality: riverside cliff exposures along the western side of St. Croix River, below a rest stop along Rt. 95 between mileposts 101 and 102, just northeast of Lookout Point, north-northeast of the town of Stillwater, Minnesota, USA (45° 05’ 03.80" North, 92° 47’ 10.33" West) |
| Date | |
| Source | Skolithos trace fossils in quartzose sandstone (Mazomanie Formation, Upper Cambrian; riverside cliff, western side of the St. Croix River, northeast of Lookout Point, Minnesota, USA) 8 |
| Author | James St. John |
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This image was originally posted to Flickr by jsj1771 at https://flickr.com/photos/47445767@N05/18379756133. It was reviewed on 19 July 2015 by FlickreviewR and was confirmed to be licensed under the terms of the cc-by-2.0. |
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| current | 19:56, 19 July 2015 | | 4,000 × 3,000 (4.32 MB) | Natuur12 (talk | contribs) | Transferred from Flickr via Flickr2Commons |
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