Cloghfin Port
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Climate exposure
This is about exposure to a nationwide pressure this habitat type carries — not a verdict on this site's own management.
Coastal habitats are exposed to sea-level rise and storm erosion. Where hard sea defences sit behind them, there's nowhere landward to retreat to — a squeeze that keeps compressing the habitat no matter how well it's managed.
Geology & landscape
Geological Period: Cretaceous, Jurassic, Paleogene, Triassic · Rock Type: Chalk, Limestone, Mudstone, Sandstone
Landscape processes: Coastal
Description
Cloghfin Port Cretaceous stratigraphy, Triassic stratigraphy Rock exposures on the foreshore at Cloghfin Port provide access to a succession of sedimentary rocks of the Mesozoic Era. During this era, which lasted approximately 183 million years, what is now Northern Ireland was inundated by a range of marine environments as it migrated between tropical latitudes 25° and 35° north. The rocks at the site range in age from the mid Triassic approximately 220 Ma to the late Cretaceous approximately 80 Ma and contain abundant invertebrate fossils. Stratigraphically, the rock succession ranges from the Mercia Mudstone Group Triassic through to the Glenann Chalk Member of the Ulster White Limestone Formation Cretaceous. The stratigraphic series, while not complete, is nonetheless remarkable. The site is of national importance due to the range of Mesozoic strata exposed, providing one of the most complete sequences in the Lame-Lough Neagh Basin and demonstrates the facies and palaeogeographic variations between this and adjacent areas. Its importance is enhanced by recent studies on the Upper Triassic rocks here, part of ongoing research into rocks of this age in the Islandmagee-Lame area. Rocks of Triassic age are represented by the Mercia Mudstone and Penarth Groups. The former consist of red to green-grey mudstones. The latter consists of the Lilstock and Westbury Formations which are composed of silt, calcareous, silty and shaley mudstones with some sedimentary structures cross bedding and slump and some sandstone often richly fossiliferous. The Westbury Formation is the top of the Triassic sediments at the site. Cretaceous rocks follow the Triassic strata. The Cretaceous is divided into the Hibemian Greensands Formation and the Ulster Whiter Limestone Formation chalk. At Cloghfin Port, the Hibemian Greensands Formation is comprised of the Belfast Marls, Island Magee Siltstones and Kilcoan Sands Members. The Belfast Marls Member is glauconitic containing the mineral 'glauconite', formed in shallow marine environments marls with shell beds and is only intermittently exposed at low tide. The presence of the fossil ammonite a type of shell fish Acanthoceras and the fossil belemnite a squid like organism Actinocamax primus in the upper part of the member have helped place the sediments within the Cenomanian stage of the Cretaceous. The Island Magee Siltstones Member is exposed as reefs on the foreshore. It is composed of grey siltstones and marls and contains numerous fossils. These include small corals, serpulid worms, shellfish and sea urchins. The overlying Kilcoan Sands Member is a glauconitic sandstone, again rich in fossils including bivalves, sea urchins and brachiopods. The Ulster White Limestone Formation chalk is well exposed at Cloghfin Port, and ranges from the Cloghfin Sponge Beds to the Glenarm Chalk Member. The thickness of the Formation at Cloghfin Port is less than within the Rathlin Basin, but the pre Larry Bane Chalk members are particularly well represented. Cloghfin Port is the type locality for the Cloghfin Sponge Bed Member which is rich in the phosphatised remains of hexactinellid sponges, giving the Member its name. The presence of glauconitised chalk pebbles indicates that an erosive surface separates the Cloghfin Sponge Beds from the next member of the sequence, the Galboly Chalk Member. The sequence continues through the Cloghastucan, Creggan, Boheeshane, Larry Bane, Ballintoy and Glenarm Chalk Members which collectively enhance this remarkable series through the Mesozoic. The sequence is truncated by Palaeogene approximately 58 million years old erosion. Recent research on the Upper Triassic formerly Rhaetic rocks have shown that they may provide important new insights into the worldwide T-J boundary extinction event through the assessment of the terrestrially derived arthropod cuticle material found here. The rocks also appear to host porpitid hydrozoans which, if confirmed, would be the only known examples of Triassic porpitids, and would also be a very rare example of ediacaran-type preservation within the Phanerozoic. To date these rocks have yielded the richest vertebrate and ichnofossil faunas of this age seen in Northern Ireland while the series contributes significantly to the proposal of Waterloo ASSI as a candidate Global Stratotype Section and Point (GSSP) for the base of the Jurassic System. https://www.daera-ni.gov.uk/publications/cloghfin-port-assi