| Summary: | The Dinantian (largely Asbian) Craven Reef Belt of North Yorkshire was a marginal facies to the shelf limestones of the stable Askrigg Block, and bridged the transition to the deeper water facies of the more rapidly subsiding Craven Basin. The reef belt is thought to have consisted of an unbroken marginal complex between Settle and Appletreewick (which was analogous to the synchronous "reef complex" of north Derbyshire). South of this belt, original upstanding reef-knolls occurred in the Cracoe area. Faulting and erosion substantially modified the reef belt, prior to its burial by Upper Bowland Shales (Pendleian) • A detailed study of the fossil biota from the surface limestones (upper B2 to P1a) of Stebden Hill reef-knoll (Cracoe), has shown the presence of six discrete benthic biotic associations, with intermediate mixed assemblages (representing zones of biotic mixing). These associations reflect both temporal and spatial (bathymetric) differentiation. A marked change in the composition of the biota during P1a times is interpreted as a response to a high stress environment induced by fault controlled partial emergence of the buildup. The shallowest water upper B2 association formed a biogenic framework. This was regarded as a modifying component of the reef-knoll and not a core facies. The framework was an indurated structure and was constructed by stromatolitic algae, lithistid sponges, tabulate corals, and bryozoans. The endemic shelly fauna contained many rare and unusual forms which were adapted to attachment on the framework. The rari ty of these shelly taxa is interpreted as due to the paucity of analogous biogenic hard-grounds in the Dinantian. Other palaeoecological phenomena discussed, includes the association of certain ostracods with cavity situations, and the predation of brachiopods.
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