The Early Carboniferous Limestone, circa 343-339 Million years ago, was deposited during a Global Highstand in sea-level in shallow, warm seas between the Variscan and Laurussian plates at which time the UK was situated circa 10°S of the paleo-equator. South Wales was located in a shallow embayment of the much deeper Tethys Ocean located far to the southeast of the proto-U.K.
Warm tropical seas in a tropical climate would result in precipitation of large volumes of calcium carbonate (CaCo3) to produce limestone. This environment would also encourage the growth of numerous shelly organisms such as cockle-like creatures and corals. A very good analogue of the Early Carboniferous environment of the UK is the Bahamas today.
Limestone is formed by the precipitation of calcium carbonate either to form the shells and hard casing of organisms or, as crystals directly from the water. The shells of the organisms can either be preserved in situ, for example as a preserved reef, or can be broken down by waves and currents into pieces that subsequently get re-deposited as Limestone.
Calcium carbonate is soluble to carbonic acid contained in rainwater and more generally in the soil as rain percolates through the Limestone it slowly dissolves the rock fabric. Often Limestone landscapes are characterised by weird shapes known as Klints & Grikes of a Karstic landscape the result of water flowing across and through the rock. Stalactites and Stalagmites (Speleothems) grown when the calcium carbonate contained in the freshwater gets re-precipitated.
The Carboniferous Limestone is exposed at the far western end of the area operated by South Wales GeoTours and is represented by the High Tor Limestone Formation. Outcrops are limited but can be seen at either Porthcawl or at Ogmore. Both these localities are close to car parks and are easily accessible on foot. Generally these outcrops are above Mean High Tide level providing access at almost any time.
The exposures were visited on two separate occasions, at Easter 2018 and Winter 2019. On both occasions I took along my Canon 5D together with the USM 24-70ml lens and the tripod to gather images to include in the design of this website and presentation materials. I made sure that I visited these outcrops when the weather was dry and bright to maximise clarity of the photos taken.