Hunts Bay Oolite is an oolitic

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 ...

limestone Limestone is a type of carbonate rock, carbonate sedimentary rock which is the main source of the material Lime (material), lime. It is composed mostly of the minerals calcite and aragonite, which are different Polymorphism (materials science) ...

geological 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 expo ...

found in the south

Wales Wales ( ) is a Countries of the United Kingdom, country that is part of the United Kingdom. It is bordered by the Irish Sea to the north and west, England to the England–Wales border, east, the Bristol Channel to the south, and the Celtic ...

region. It is named after Hunts Bay on the Gower peninsula, south-south west of Bishopston, where a significant amount of the limestone forms the cliffs there. Bracelet Bay - geograph

Hunts Bay Oolite is a sub-group of the Pembroke Limestone Group which itself is part of the Carboniferous Limestone Supergroup. Oolite means 'egg stone': very small grains (up to 2mm) form by accumulating precipitated minerals, usually

calcium carbonate Calcium carbonate is a chemical compound with the chemical formula . It is a common substance found in Rock (geology), rocks as the minerals calcite and aragonite, most notably in chalk and limestone, eggshells, gastropod shells, shellfish skel ...

. These ooids, created in a warm, tropical environment, are the precursors to the limestone. The Hunts Bay Oolite extends from Pembroke in the West to

Monmouth Monmouth ( or ; ) is a market town and community (Wales), community in Monmouthshire, Wales, situated on where the River Monnow joins the River Wye, from the Wales–England border. The population in the 2011 census was 10,508, rising from 8 ...

and

Chepstow Chepstow () is a town and community in Monmouthshire, Wales, adjoining the border with Gloucestershire, England. It is located on the tidal River Wye, about above its confluence with the River Severn, and adjoining the western end of the ...

in the East and northwards into the Dowlais Limestone Formation around

Merthyr Tydfil Merthyr Tydfil () is the main town in Merthyr Tydfil County Borough, Wales, administered by Merthyr Tydfil County Borough Council. It is about north of Cardiff. Often called just Merthyr, it is said to be named after Tydfil, daughter of K ...

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 ...

, such as

brachiopod Brachiopods (), phylum (biology), phylum Brachiopoda, are a phylum of animals that have hard "valves" (shells) on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear e ...

s and

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 associated with a shallow sea environment, can be found in the rock. East of the

South Wales Coalfield The South Wales Coalfield () extends across Pembrokeshire, Carmarthenshire, Swansea, Neath Port Talbot, Bridgend, Rhondda Cynon Taf, Merthyr Tydfil, Caerphilly, Blaenau Gwent and Torfaen. It is rich in coal deposits, especially in the South Wales ...

and in the south east the rock is increasingly dolomitised (where some

calcium Calcium is a chemical element; it has symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to it ...

is replaced by

magnesium Magnesium is a chemical element; it has Symbol (chemistry), symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 ...

). This subgroup was deposited in equatorial seas largely during the Holkerian (British regional) substage of 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, from 337 to 333.5 million years ago.

References

* {{cite web, title= Fossilworks: Gateway to the Paleobiology Database, author= ((Various Contributors to the Paleobiology Database)), url= https://www.fossilworks.org, access-date= 8 July 2014, 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 Wales

See also

References