Cloghastucan
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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 · Rock Type: Chalk, Flint, Limestone
Landscape processes: Coastal
Description
Cloghastucan Cretaceous stratigraphy The area is of special scientific interest because of its important geology. The site is the type locality of the Galboly Chalk Member of the Ulster White Limestone Formation. The site demonstrates sedimentation variations in the Lame-Lough Neagh Basin during the Santonian Stage of the late Cretaceous. At this time, approximately 85 million years ago, a rise in global sea level inundated much of the land surface with shallow, warm seas in which the limestone was deposited. While variations in limestone thickness were controlled by pre existing topography, correlation of outcrops of the Galboly Chalk Member demonstrates that the earliest limestone development in the Rathlin Basin and the Lame-Lough Neagh Basin was almost contemporaneous, although absolute thicknesses vary. By reference to the type section, the relative amount of non-sequence can be determined for any locality and an areal pattern can be determined that reflects the tectonic controls on Cretaceous sedimentation. At Cloghastucan the rocks are exposed in a roadside rock pillar and in slipped blocks on the foreshore. The pillar is the type section for the Galboly Chalk Member and is the thickest section of the member at 5.85 m. The base of the Member is not exposed in the pillar, but is contained within the blocks on the foreshore. The lowest limestone is creamy and contains many dark irregular marly partings. Occasional glauconite grains are found concentrated along these partings. Flint nodules first occur 0.60 to 0.90 m above the base, but their development is not typical. Many of them are only partially formed and are whitish in colour; the more normal black flints develop 1.52 m from the base. In the next 2.13 m of the sequence six distinct flint bands give a distinguishing character to this part of the succession. The sediment 3.66 m above the base is wavy-bedded and is predominantly weathered out. The remaining 2.19 m of the sequence contain six bands of flint similar in character to those below and terminate at an erosion surface with scattered small flints. This is taken as the boundary with the younger Cloghastucan Chalk Member and marks a faunal change from the crinoid Uintacrinus Zone to the crinoid Marsupites Zone. Prismatic fragments of the bivalve mollusc Inoceramus are abundant and slender specimens of Actinocamax verus are the only belemnites recorded. Occasional ossicles of the crinoids Uintacrinus and Bourgueticrinus can be found, but the commonest zonal indicators are shape variants of Echinocorys, a sea urchin. https://www.daera-ni.gov.uk/publications/cloghastucan-assi