Castle Point ASSI

The limestone rocks exposed in the cliffs and rock platforms between Ballycastle Harbour and Port Calliagh belong to the Ulster White Limestone Formation and are overlain by basalt of the Antrim Lava Group. The Ballycastle and Port Calliagh Chalk Members have their type localities within the site. The available evidence indicates the Chalk Members were deposited in a warm, shallow sea during the Cretaceous, some 80 million years ago. They represent the youngest Cretaceous (Campanian to Maastrichtian) strata preserved in Northern Ireland (and indeed in Ireland) with the Ballycastle Chalk Member being the younger of the two.

It is one of the only localities that readily yield microscopic marine fossils, or foraminiferans, of this age. The taxa Globorotalites conicus and Neoflabellina rugosa, which are unrecorded post Campanian, and Osangularia lens which is exclusively Maastrichtian, indicate the rocks span the Campanian – Maastrichtian boundary.

The area is also notable for its inter-tidal communities. An extensive limestone, wave cut platform on a moderately exposed shore supports many wide shallow rock pools. The intertidal area is characterised by red algae and patellobarnacle biotopes although barnacles themselves are scarce due to the soft nature of the substrate. Pockets of localised shelter allow the growth of spiral wrack seaweed.