File:Encrinite (crinoidal limestone) (Ft. Payne Limestone, Lower Mississippian; Lake Cumberland, Kentucky, USA) 13 (34787369746).jpg
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| Description |
Encrinite from the Mississippian of Kentucky, USA. The Ft. Payne Formation of southern Kentucky is richly fossiliferous and is dominated by crinoids. Crinoids ("sea lilies") are sessile, benthic, filter-feeding, marine invertebrates that were abundant in Paleozoic oceans. The group nearly went extinct at the Permian-Triassic mass extinction 251 million years ago. Crinoids are not common in modern oceans - they are usually deep-water forms now, but some shallow-water forms also exist today. A crinoid is essentially a starfish on a stick. The stick, or stem, lifts the organism to a moderately high tier above the seafloor, which is conducive to non-competitive filter feeding. The flower-like "head" of the crinoid consists of numerous cemented calcite plates that surround the digestive system and other soft parts. The arms are feather-like and are the structures that engage in filter-feeding. In the fossil record, crinoid stems are common, whereas crinoid heads are uncommon to rare, because they disaggregate quickly after death. Individual pieces of a crinoid stem are called columnals - they are usually somewhat shaped like poker chips. Each columnal is composed of a single crystal of calcite (CaCO3 - calcium carbonate). The limestone shown above is almost entirely composed of crinoid pieces. Such crinoidal limestones are called "encrinites". Overall, the lithology of this sample is partially chertified crinoidal grainstone. The jumble at center is a partially disintegrated camerate crinoid head. Classification: Animalia, Echinodermata, Crinoidea Stratigraphy: Ft. Payne Formation, Osagean Stage, upper Lower Mississippian Locality: lakeside exposure on the northeastern side of the Gross Creek armlet of the southern Indian Creek arm of southwestern Lake Cumberland, northern Clinton County, southern Kentucky, USA See info. at: <a href="https://en.wikipedia.org/wiki/Encrinite" rel="nofollow">en.wikipedia.org/wiki/Encrinite</a> and <a href="https://en.wikipedia.org/wiki/Crinoid" rel="nofollow">en.wikipedia.org/wiki/Crinoid</a> |
| Date | |
| Source | Encrinite (crinoidal limestone) (Ft. Payne Limestone, Lower Mississippian; Lake Cumberland, Kentucky, USA) 13 |
| 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@N05/34787369746 (archive). It was reviewed on 12 October 2019 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0. |
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| current | 04:02, 12 October 2019 | | 3,014 × 2,123 (3.73 MB) | Ser Amantio di Nicolao (talk | contribs) | Transferred from Flickr via #flickr2commons |
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