Robeston Wathen Quarries
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Geology & landscape
Geological Period: Ordovician, Silurian · Rock Type: Limestone, Mudstone
Description
Description The type locality of the Ashgill Robeston Wathen Limestone, and an important section in the Ashgill of South Wales. The Robeston Wathen Limestone is extremely rich in corals, particularly halysitids, and contains rare brachiopods. It is possibly a lateral correlative of part of the Shoalshook Limestone in a radically different facies. This is the only locality in South Wales where evidence is found for a break between the Shoalshook Limestone and the Slade and Redhill mudstones. The complete succession, through the Robeston Wathen Limestone, Shoalshook Limestone and Slade and Redhill mudstones into the Llandovery makes this a key Ordovician stratigraphic locality in Wales. In layman’s terms, the interest of this site may be expressed more simply, and such a statement is provided below. This should not be taken as definitive and further information as to details of the interest can be obtained from the Countryside Council for Wales. This locality is the standard reference section for the Robeston Wathen Limestone, a local variant of the Upper Ordovician Shoalshook Limestone. The limestones seen here were deposited beneath a shallow sea which covered the area some 440 million years ago and are rich in species of corals and shelly fossils known as brachiopods which are rare elsewhere in Britain. The limestones are overlain by deposits of mudstone and by strata of Silurian age. The site therefore provides an almost complete section through the Ashgill Stage of the Ordovician and allows correlations to be made with other areas of the country where rocks of similar age are exposed.