Bardahessiagh
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Geology & landscape
Geological Period: Ordovician, Silurian
Description
Bardahessiagh Ordovician stratigraphy The southern flank of Craigbardahessiagh hill contains a highly fossiliferous sequence of Ordovician marine shelf or platform sediments some 450 million years old M.y.. Although poorly exposed, very diverse shelly faunas have been collected from here which are of considerable importance in understanding the geography of the world in Ordovician times. The sequence also records a long continuous subsidence history for this platformal area from Upper Ordovician, Caradoc 454 M.y., to Lower Silurian, Llandovery 420 M.y., times. The fossil faunas were first described by Major-General Portlock between 1837 and 1843, while subsequent publications have dealt with various fossil groups. The series of sandstones, mudstones and siltstones contain a rich array of fossil brachiopods, trilobites, bivalves, gastropods, bryozoans, corals, and cephalopods. Over 50 new species were first described from specimens collected here. Many additional new species collected in 1992 still await definitive descriptions but it is already recognised as one of the most diverse Caradoc age fossil sites. Overall, the major fossil assemblage can best be compared with sites described from the Girvan area of Scotland and a number of sites in the Appalachian Mountains in the United States. The site thus clearly shows that the Pomeroy area forms part of the former province which existed to the north of the Iapetus suture. This suture marks the line of closure of the former Iapetus Ocean which finally disappeared during Silurian times. https://www.daera-ni.gov.uk/publications/bardahessiagh-assi