Modern bryomol-sediments in a cool-water, high-energy setting: the inner shelf off Northern Brittany

The inner shelf off Roscoff/North Brittany, France situated in the Western English Channel, provides a unique facility for studying modern cold water BRYOMOL-carbonate deposits in the North Atlantic. High tidal gauge with ext reme strong tidal currents, which effect the well-mixed water column throug hout the year, and strong, seasonal storms characterize the conditions of t he area. The shelf is seperated in two carbonate production zones: Boulder fields and sand fields. The main production areas are the sand fields with an intensive epifaunal and infaunal colonization by bivalves and the bryozo an thickets of Cellaria spp. and their associated epifauna. The most benefi cial and dominant strategies of the sessile benthos are erect flexible and encrusting growth habits. The study area is partitioned in two zones: (1) the coarse sediment blanket typified by active sediment generation and little accumulation, and (2) th e shell dune Trezen ar Skoden, characterized by accumulated sediments. Sedi ment transport and distribution of facies areas are controlled by the stron g semidiurnal tidal current regime and episodically severe storms. As a res ult of these high energy processes of redeposition the autochthonous sedime nt particles are physically reworked and redeposited while in calmer period s deposition and biological destruction of the components occur. The Holocene development of the sea level has been of crucial influence to the costal morphology and the establishment of different carbonate producti on centers. The benthic communities produce with their carbonate skeletons the first biogenic sediment and provide substrates for colonization of epi- and endofauna. Changes in the current patterns and the morphology of the s ea bottom resulted in the origin of the shell dune Trezen ar Skoden.