Transport of Late Pleistocene loess particles by katabatic winds during the lowstands of the English Channel

Abstract

Studies of the submerged Pleistocene conglomerate cored and dredged in the English Channel show that it resulted from the cementation of stony beaches under a loess blanket. Although the loess cover was later washed out by younger transgressions, the northern limit of the conglomerate corresponds to the original offshore extension of the loess deposits. Compilation of offshore and onshore altitudes of the limits of these deposits shows that loess was deposited by low-level wind fields never thicker than 200 m. Mapping surveys show that the present limits of loess are probably close to their original boundaries. The past proximity of the British Ice Sheet, the accumulation of dusty sediments coating north-facing cliffs of Brittany originating in the outwash of the British–Irish Ice Sheet and in the palaeo-rivers of the English Channel, as well as the southeastward orientation of the palaeo-winds deduced from particle size analysis and heavy minerals distribution, suggest that large volumes of loess were transported by strong katabatic winds blowing from the northern ice-covered regions towards Brittany and Normandy. The existence of katabatic winds is also consistent with the drift of ice rafts that transported Icelandic basalts now grounded in Brittany and possibly with the orientation of Homo neandertalensis shelters.