The “Turritella Layer”: A Potential Proxy of a Drastic Holocene Environmental Change on the North–East Atlantic Coast

A collection of data including sub-bottom VHR seismic (Seistec boomer), bathymetry and cores, was conducted in three sea lochs of the north west coast of Scotland, as part of an investigation of the sedimentological and climatic change records since the Last Glacial Maximum. Five acoustic facies have been correlated to the sediment of the core MD04-3204 and interpreted in terms of glacial activity, ice retreat and subsequent Holocene sedimentation. Grain size, pollen, foraminifera, geochemical analyses together with 14C dating, indicate a complex series of palaeoclimate changes in the loch since the Last Glacial Maximum including “Rapid Climate Changes” described in literature. A characteristic acoustic reflector, identified into the holocene sedimentary deposit, occurring into the different studied lochs, corresponds to a unique Turritella layer. A similar reflector has been identified on the continental shelf of South Brittany and is correlated to a Turritella layer. This Turritella layer seems to be related, in both case, to a drastic environmental change beginning around the 8,200 year BP cold event and finishing abruptly at 7,500 year BP in the North Atlantic.