• Source: Eyam Limestone

The Eyam Limestone (formerly known as the Cawdor Group, Cawdor Limestone or Eyam Group) is a geologic formation in the Peak District, England. It preserves fossils dating back to the Viséan stage of the Carboniferous period, and represents a marine environment.




Depositional environment


At the time of deposition, Britain was just south of the equator (<5° S) and part of the Euramerica continent. Study of the growth rings of fossil wood from other localities indicate that the British Isles had a monsoonal climate during the early Carboniferous, with tropical rainfall seasonality. The Eyam Limestone was deposited on an extensive, thick carbonate ramp and platform on the northeast margin of the Widmerpool Gulf (an extensive basin which existed as an area of open water during the time of deposition). Reefs and their associated fore-reef and lagoonal environments are represented in the Eyam Limestone, with crinoids dominating the reef and providing habitats for other animals. The presence of photosymbiotic coral and micritic envelopes on some crinoid ossicles indicates the formation was deposited within the photic zone in a marine environment of normal salinity. The presence of the xenacanth Bransonella has been suggested to imply freshwater influence as xenacanths live mainly in freshwater habitats, however its presence in other marine formations suggests that Bransonella was a marine animal unlike its relatives.
Apatite crystals formed by the recrystallization of phosphatic overgrowths are present on some conodont elements from the formation. As phosphatogenesis only occurs in the anoxic-oxic boundary while apatite precipitation occurs in the top few centimeters of the sediment column, this reveals that shallow sediment with low geothermal temperatures and dysoxic conditions were present in the Eyam Limestone.




Fossil content






= Cartilaginous fish

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= Conodonts

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= Invertebrates

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Arthropods




Brachiopods




Bryozoans




Cnidarians




Echinoderms




Molluscs





See also



List of fossiliferous stratigraphic units in England




References



Various Contributors to the Paleobiology Database. "Fossilworks: Gateway to the Paleobiology Database". Archived from the original on 25 March 2022. Retrieved 17 December 2021.

Kata Kunci Pencarian:

• Eyam Limestone
• Eyam
• Peak Limestone Group
• Squatinactis
• Acanthorhachis
• Cooleyella
• Listracanthidae
• Reesodus
• Geology of the Peak District National Park
• List of fossiliferous stratigraphic units in England