Imprint of late Pleistocene continental processes visible in ice-rafted grains from the central Arctic Ocean

Abstract

Ice-rafted quartz sand grains of sediment samples representing marine isotope stages (MIS) 3 and 4 from the Lomonosov Ridge, Arctic Ocean, are here analysed with a scanning electron microscope (SEM) to characterise processes in the sediment source area. The microtextural characteristics of the grains were observed and their microtexture frequencies calculated. Specific sets of microtextures were identified and classified (Group I–III) using principal component analysis (PCA) and cluster analysis. The statistically analysed microtextural data were used to identify signals of continental processes that operated during the late Pleistocene (MIS 4 to MIS 3) in the Eurasian Arctic. The microtextures of Group I generally formed as a result of prolonged fluvial/alluvial or aeolian transport. The glacial microtextures of Groups II and III indicate subglacial conditions and transport. Based on the data, two principal components seem to characterise late Pleistocene continental environmental conditions – glacial and non-glacial. There is a signal of non-glacial continental processes in the ice-rafted grains at around 62, 64 and 67 ka ago. A signal of subglacial processes was observed in the grains at around 26, 34, 42 and 45 ka and, concurrent with non-glacial, at around 62 and 64 ka ago. We suggest that these signals in MIS 4 sediments are related to deglaciation with an increased supply of glacial sediment to the Arctic Ocean, whereas during MIS 3 they were probably related more to iceberg calving from the oscillating Barents-Kara ice sheet.