The Eyam Limestone (formerly known as the Cawdor Group, Cawdor Limestone or Eyam Group) is a

geologic formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ...

in the

Peak District The Peak District is an Highland, upland area in central-northern England, at the southern end of the Pennines. Mostly in Derbyshire, it extends into Cheshire, Greater Manchester, Staffordshire, West Yorkshire and South Yorkshire. It is subdivi ...

England England is a Countries of the United Kingdom, country that is part of the United Kingdom. It is located on the island of Great Britain, of which it covers about 62%, and List of islands of England, more than 100 smaller adjacent islands. It ...

. It preserves

fossils A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

dating back to the

Viséan The Visean, Viséan or Visian is an age in the ICS geologic timescale or a stage in the stratigraphic column. It is the second stage of the Mississippian, the lower subsystem of the Carboniferous. The Visean lasted from to Ma. It follows ...

stage of the

Carboniferous The Carboniferous ( ) is a Geologic time scale, geologic period and System (stratigraphy), system of the Paleozoic era (geology), era that spans 60 million years, from the end of the Devonian Period Ma (million years ago) to the beginning of the ...

period, and represents a marine environment.

Depositional environment

At the time of deposition, Britain was just south of the

equator The equator is the circle of latitude that divides Earth into the Northern Hemisphere, Northern and Southern Hemisphere, Southern Hemispheres of Earth, hemispheres. It is an imaginary line located at 0 degrees latitude, about in circumferen ...

(<5° S) and part of the

Euramerica Laurasia () was the more northern of two large landmasses that formed part of the Pangaea supercontinent from around ( Mya), the other being Gondwana. It separated from Gondwana (beginning in the late Triassic period) during the breakup of Pa ...

continent. Study of the growth rings of fossil wood from other localities indicate that the British Isles had a

monsoon A monsoon () is traditionally a seasonal reversing wind accompanied by corresponding changes in precipitation but is now used to describe seasonal changes in Atmosphere of Earth, atmospheric circulation and precipitation associated with annu ...

al climate during the

early Carboniferous Early may refer to: Places in the United States * Early, Iowa, a city * Early, Texas, a city * Early Branch, a stream in Missouri * Early County, Georgia * Fort Early, Georgia, an early 19th century fort Music * Early B, stage name of Jamaican d ...

, 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).

Reef A reef is a ridge or shoal of rock, coral, or similar relatively stable material lying beneath the surface of a natural body of water. Many reefs result from natural, abiotic component, abiotic (non-living) processes such as deposition (geol ...

s and their associated fore-reef and

lagoon A lagoon is a shallow body of water separated from a larger body of water by a narrow landform, such as reefs, barrier islands, barrier peninsulas, or isthmuses. Lagoons are commonly divided into ''coastal lagoons'' (or ''barrier lagoons'') an ...

al environments are represented in the Eyam Limestone, with

crinoid Crinoids are marine invertebrates that make up the class Crinoidea. Crinoids that remain attached to the sea floor by a stalk in their adult form are commonly called sea lilies, while the unstalked forms, called feather stars or comatulids, are ...

s dominating the reef and providing habitats for other animals. The presence of

photosymbiotic Photosymbiosis is a type of symbiosis where one of the organisms is capable of photosynthesis. Examples of photosymbiotic relationships include those in lichens, plankton, ciliates, and many marine organisms including corals, fire corals, giant ...

coral Corals are colonial marine invertebrates within the subphylum Anthozoa of the phylum Cnidaria. They typically form compact Colony (biology), colonies of many identical individual polyp (zoology), polyps. Coral species include the important Coral ...

and micritic envelopes on some crinoid ossicles indicates the formation was deposited within the

photic zone The photic zone (or euphotic zone, epipelagic zone, or sunlight zone) is the uppermost layer of a body of water that receives sunlight, allowing phytoplankton to perform photosynthesis. It undergoes a series of physical, chemical, and biological ...

in a

marine environment A marine habitat is a habitat that supports marine life. Marine life depends in some way on the saltwater that is in the sea (the term ''marine'' comes from the Latin ''mare'', meaning sea or ocean). A habitat is an ecological or environmen ...

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 Apatite is a group of phosphate minerals, usually hydroxyapatite, fluorapatite and chlorapatite, with high concentrations of Hydroxide, OH−, Fluoride, F− and Chloride, Cl− ion, respectively, in the crystal. The formula of the admixture of ...

crystals formed by the recrystallization of phosphatic overgrowths are present on some

conodont Conodonts, are an extinct group of marine jawless vertebrates belonging to the class Conodonta (from Ancient Greek κῶνος (''kōnos''), meaning " cone", and ὀδούς (''odoús''), meaning "tooth"). They are primarily known from their hard ...

elements from the formation. As phosphatogenesis only occurs in the anoxic-oxic boundary while apatite

precipitation In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls from clouds due to gravitational pull. The main forms of precipitation include drizzle, rain, rain and snow mixed ("sleet" in Commonwe ...

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

Conodonts

Invertebrates

Arthropods

Brachiopods

Bryozoans

Cnidarians

Echinoderms

Molluscs

References

* {{cite web, title= Fossilworks: Gateway to the Paleobiology Database, author= ((Various Contributors to the Paleobiology Database)), url= https://www.fossilworks.org, access-date= 17 December 2021, archive-date= 25 March 2022, archive-url= https://web.archive.org/web/20220325060448/http://www.fossilworks.org/cgi-bin/bridge.pl?action=home, url-status= live Carboniferous System of Europe Carboniferous England Limestone formations of the United Kingdom Carboniferous southern paleotropical deposits