INFESTATION OF HARDGROUNDS, ROUND HILL, CLARENDON

The prograding succession of the late Miocene, Round Hill Beds, contains four lithofacies (Units A-D). Unit A is a sequence of nodular, bedded limestone. The nodular limestones follows the shape of the burrow system made by crustaceans, Thalassinoides, they also form a series of hardgrounds that are infested with various borings inclusive of Trypanites, Gastrochaenolites and two others yet to be identified. These hardgrounds are also encrusted with barnacles, oysters and algae. The palaeoenvironment have previously been interpreted as open marine on a carbonate slope. However this preliminary interpretation should be extended to include fine-grained micritic limestones which contain possible freshwater gastropods underlain by a lignite-rich bed. Units B-D appears not to have these hardground sequences, and the palaeoenvironment varies from open marine to terrestrial.