Mineral magnetic and geochemical records of late Glacial climatic change from two northwest European carbonate lakes

We present the results of mineral magnetic measurements and geochemical ana lyses of late Glacial sediments from two marl-precipitating lakes in the No rthwest of England. Mineral magnetic assemblages dominated by detrital and/ or authigenic ferrimagnetic minerals, and enhanced delivery of metal elemen ts, characterise a lower (Oldest Dryas) and an upper (Younger Dryas) phase of catchment instability, with detrital clay and silt sedimentation. Magnet ic mineral assemblages with lower concentrations of finer ferrimagnetic gra ins characterise the authigenic carbonate sediments (marls). The marls indi cate both enhanced lake productivity and catchment stability in response to prevailing warm conditions during the Bolling - Allerod Interstadial. The Bolling - Allerod marl phase contains two short-term, low amplitude shifts characterised by changes in the concentration and the size of ferrimagnetic grains. These shifts may represent the Older Dryas and the Amphi-Atlantic Oscillation, short-lived Northern hemisphere climatic deteriorations. Overa ll, the results suggest that marl lakes are sensitive indicators of Lategla cial climatic change, and that these changes are readily identifiable throu gh the use of mineral magnetic measurements.