Bellanaleck
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Geology & landscape
Geological Feature: Rock Outcrop · Mining / Industrial: Quarry · Geological Period: Carboniferous · Rock Type: Limestone
Description
Bellanaleck Carboniferous stratigraphy The Carboniferous rocks exposed in Bellanaleck Quarry are one of only two occurrences of Waulsortian mound limestones in Northern Ireland. They contain a diverse fossil fauna that includes, recorded for the first time in Northern Ireland, a suite of trilobites that are oflate Toumaisian age, some 342 million years old My. The term Waulsortian refers to a submarine reef formation with distinctive associated rock and fossil animal characters of a particular age, that being late Tournaisian to early Visean. The dominant rock is a fine-grained limestone which is riddled with laminated calcite crusts associated with large unbroken fronds of bryozoa. This assemblage is thought to represent the deepest environment in the development of the mound and is associated with bryozoa, together with crinoid debris and an abundant and diverse fauna of brachiopods, of which 19 species occur. Unfortunately this brachiopod assemblage is not fully diagnostic of age. The presence of trilobites is particularly noteworthy. The age of the rocks has been estimated as no younger than the Arundian, 339 My, and no older than the base of the upper Tournaisian, 342 My. They are thus within the age range for the Waulsortian. Rocks of this age are rare in Northern Ireland, as elsewhere there is good evidence of marine regression in these times and exposure of older Carboniferous sedimentary rocks and hence non-deposition in this area. Despite the isolated nature of the limestone exposure here, the area is one of the most important geological localities in the Carboniferous outcrop of Northern Ireland. This occurrence of Waulsortian limestones is some 60km north of the limit formerly imposed on the development of this facies in Ireland, and is one of the two most northerly occurrences of the Waulsortian in Ireland, great Britain and Western Europe. It is the only locality in Northern Ireland where an early Chadian age is proven. https://www.daera-ni.gov.uk/publications/bellanaleck-assi