Detrital zircon U-Pb ages reveal ice sheet and North Sea drainage driven dust source variability recorded in late Quaternary loess deposits at Pegwell Bay, SE England

Loess deposits are the most widespread terrestrial archive of past climate and environmental change. While several tens of metres thick loess-palaeosol sequences in central and eastern Europe record multiple glacial-interglacial cycles, substantially thinner deposits along the English Channel in north-western Europe may provide valuable “snapshots” of abrupt climatic and environmental changes in areas proximal to the North Atlantic. Recently, high-resolution luminescence dating of loess deposits at Pegwell Bay, SE England has enabled constraint of the timing of dust fall over south-east England to 25-19 ka when the British-Irish and Fennoscandian Ice sheets had coalesced and the associated strengthened high pressure system favoured dust entrainment from the exposed southern North Sea basin. Two phases of greatly enhanced dust deposition at the site are centred around 25-23.5 ka and 20-19 ka, contemporaneous with changes in North Sea ice sheet extent and ice dammed lake drainage. Such changes may have triggered abrupt flood events that would have greatly enhanced sediment supply potentially overriding the input from other sediment sources, e.g. major rivers like the Rhine. However, while the temporal link between ice sheet and dust dynamics is striking, this possibility remains untested due to lack of sufficiently source diagnostic provenance analyses of loess along the North Sea and Channel coasts. The use of single grain detrital zircon U-Pb age assemblages can discriminate different sources to loess in suitable settings. Given the geochronological heterogeneity of terranes that account for sediment input into the North Sea basin during the late last glacial ranging from Baltica in the east, Cadomia-Armorica in the south and Laurentia-Ganderia-Meguma-Avalonia in the north and west, detrital zircon ages have great promise to link changes in North Sea drainage with dust source activity. As such, high n detrital zircon age assemblages have here been analysed from two samples of loess deposited at Pegwell Bay during the two phases of enhanced dust deposition. Preliminary results indicate that glacifluvial sediments derived from both Scandinavia and Britain combined with input from major rivers draining central and western continental Europe act as dust source during the first phase while glacifluvial sediments from Britain dominate during the second phase linked to the final abrupt decay of the North Sea ice lobe. These findings based on single grain detrital zircon data alone highlight the method’s potential to detect abrupt dust source variability in a favourable scenario of heterogenous source terranes. They also emphasise the importance of abrupt changes in ice sheets and their drainage in controlling wider-scale, rapid and substantial changes in atmospheric dust emission in higher latitudes, and by extension possible subsequent climatic and environmental effects.