File:Mudcracks on base of sandstone bed (Kayenta Formation or Navajo Sandstone, Lower Jurassic; Potash-Poison Spider dinosaur tracksite, Williams Bottom, southwest of Moab, Utah, USA) 22 (32309976284).jpg
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| Description |
Mudcracks are diagnostic sedimentary structures indicating subaerial exposure of sediment surfaces, with alternating wet & 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 sediments, fine-grained carbonate sediments, and in some evaporitic settings. 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 & shape. Shown above are ancient mudcracks on the bottom of a sandstone bed. Shales (= lithified mud & clay) originally floored the sandstone. The mudcracks themselves are expressed as ridges on the base of the bed. Stratigraphy: talus block derived from the Kayenta Formation or the Navajo Sandstone, Lower Jurassic Locality: talus block on slope of Kayenta Formation, Potash Road/Poison Spider Dinosaur Tracksite, just north of the Poison Spider Trailhead parking lot, adjacent to Williams Bottom along the Colorado River, next to Potash Road (Rt. 279), southwest of the town of Moab, southern Grand County, eastern Utah, USA (vicinity of 38° 32' 01.09" North latitude, 109° 36' 29.92" West longitude) |
| Date | |
| Source | Mudcracks on base of sandstone bed (Kayenta Formation or Navajo Sandstone, Lower Jurassic; Potash-Poison Spider dinosaur tracksite, Williams Bottom, southwest of Moab, Utah, USA) 22 |
| 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@N05/32309976284 (archive). It was reviewed on 2 December 2018 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0. |
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| Date/Time | Thumbnail | Dimensions | User | Comment | |
|---|---|---|---|---|---|
| current | 07:41, 2 December 2018 | | 4,000 × 3,000 (9.56 MB) | Rudolphous (talk | contribs) | Transferred from Flickr via #flickr2commons |
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