Late Weichselian and Holocene climatic and local controls on aeolian deposition inferred from decomposing grain size-shape distributions
van Hateren, J.A.
van der Woude, J.
van Balen, R.T.
Aeolian deposits form rich archives of climatic and environmental changes, which have not been fully explored. In this study, results from end-member modelling of grain size-shape distributions were combined with palynological records to reconstruct sedimentary environments and transport mechanisms, and to distinguish climatically-caused from local or system-intrinsic variabilities. We compare results from Weichselian aeolian type locality Lutterzand in the Eastern Netherlands to those of a aeolian site in the Central Netherlands. Four grain size-shape end-members were determined. These represent coarse fluvial or aeolian bedload, fine aeolian bedload, aeolian modified saltation and aeolian suspension (loess) transport mechanisms. We assume that synchronous changes in end-member composition at the two sites are effects of climate change; non-synchronous changes are the result of local or system-intrinsic variability, which are attributed to the influence of the paleo-topographic position on local humidity of the sediment bed. Our results show that during the final stage of the Late Pleniglacial, a change from polar desert to wet sand-sheet paleo-environment occurred, which implies increased humidity and decreased wind speed that may be linked to a northward shift of the polar front preceding warming during the Bølling time interval. The deposition of loess during the Bølling implies further climate amelioration and a concomitant increase in vegetation density. The landscape re-opens during the Older Dryas. The high degree of sediment sorting and near absence of modified saltation and suspension transport mechanisms/end members during this phase are indicative of an undulating aeolian topography and the formation of incipient dunes, for which sparse vegetation forms growth nuclei. A high loess content reveals that the Betula phase of the Allerød was humid. The subsequent Allerød Pinus phase was drier, potentially due to Pinus-induced drought and wildfires. The deposits of the Younger Dryas reflect a paleo-environment similar to that of the Older Dryas. Land use-induced sand-drifting in the Middle Ages is differentiated from the Late-Weichselian aeolian depositional phases by a higher proportion of suspension and modified saltation end members, reflecting wetter climate and denser vegetation during the Holocene.
Aeolian sediment transport mechanisms
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Grain size-shape distributions
Geological Survey Netherlands
Quaternary Science Reviews, 287 (287), 1-24