Climate control on the evolution of Late Pleistocene alluvial-fan and aeolian sand-sheet systems in NW Germany JANINE MEINSEN, JUTTA WINSEMANN, JULIA ROSKOSCH, CHRISTIAN BRANDES, MANFRED FRECHEN, STEFAN DULTZ AND JÜRGEN BÖTTCHER Meinsen, J., Winsemann, J., Roskosch, J., Brandes, C., Frechen, M., Dultz, S. & Böttcher, J. 2014 (January): Climate control on the evolution of Late Pleistocene alluvial-fan and aeolian sand-sheet systems in NW Germany. Boreas, Vol. 43, pp. 42–66. 10.1111/bor.12021. ISSN 0300-9483. The Late Pleistocene was characterized by rapid climate oscillations with alternation of warm and cold periods that lasted up to several thousand years. Although much work has been carried out on the palaeoclimate reconstruction, a direct correlation of ice-core, marine and terrestrial records is still difficult. Here we present new data from late Middle Pleniglacial to Lateglacial alluvial-fan and aeolian sand-sheet deposits in northwest- ern Germany. Records of Late Pleniglacial alluvial fans in central Europe are very rare, and OSL dating is used to determine the timing of fan aggradation. In contrast to fluvial systems that commonly show a delay between climate change and incision/aggradation, the small alluvial-fan systems of the Senne area responded rapidly to climatic changes and therefore act as important terrestrial climate archives for this time span. The onset of alluvial-fan deposition correlates with the climate change from warm to cold at the end of MIS 3 (29.33.2 ka). Strong fan progradation started at 24.42.8 ka and may be related to a period of higher humidity. The vertical stacking pattern of sedimentary facies and channel styles indicate a subsequrent overall decrease in water and sediment supply, with less sustained discharges and more sporadic runoffs from the catchment area, corre- sponding to an increasing aridity in central Europe during the Late Pleniglacial. Major phases of channel incision and fan aggradation may have been controlled by millennial-scale Dansgaard–Oeschger cycles. The incision of channel systems is attributed to unstable climate phases at cold–warm (dry–wet) or warm–cold (wet–dry) transitions. The alluvial-fan deposits are bounded by an erosion surface and are overlain by aeolian sand-sheets that were periodically affected by flash-floods. This unconformity might be correlated with the Beuningen Gravel Bed, which is an important marker horizon in deposits of the Late Pleniglacial resulting from deflation under polar desert conditions. The deposition of aeolian sand-sheet systems (19.62.1 to 13.11.5 ka) indicates a rapid increase in aridity at the end of the Late Pleniglacial. Intercalated flash-floods deposits and palaeosols (Finow type) point to temporarily wet conditions during the Lateglacial. The formation of an ephem- eral channel network probably marks the warm-cold transition from the Allerød to the Younger Dryas. Janine Meinsen, Jutta Winsemann (winsemann@geowi.uni-hannover.de), Julia Roskosch and Christian Brandes, Institut für Geologie, Leibniz Universität Hannover, Callinstrasse 30, D-30167 Hannover, Germany; Janine Meinsen, Landesamt für Bergbau, Energie und Geologie (LBEG), Stilleweg 2, D-30655 Hannover; Manfred Frechen, Leibniz Institute for Applied Geophysics (LIAG), Geochronology and Isotope Hydrology, Stilleweg 2, D-30655 Hannover, Germany; Stefan Dultz and Jürgen Böttcher, Institute of Soil Science, Leibniz Universität Hannover, Herrenhäuser Strasse 2, D-30419 Hannover, Germany; received 27th February 2012, accepted 6th March 2013. The climate during the Late Pleistocene was charac- terized by rapid oscillations between stadials and interstadials, which lasted up to several thousand years. These high-frequency climate oscillations are referred to as Dansgaard–Oeschger cycles and are associated with Heinrich Events during which sudden iceberg discharges into the North Atlantic occurred. This high-resolution record of the Late Pleistocene climate is provided by the Greenland ice-core chronol- ogy. The most recently acquired data of core GICC05 provide an annually resolved climate record of the last 60 ka (Andersen et al. 2006; Rasmussen et al. 2006; Svensson et al. 2008), and 17 interstadials/stadials have been reconstructed for the North Atlantic region (Svensson et al. 2008). However, although much work has been carried out on the climate reconstruction of the Late Pleistocene, a direct correlation of ice-core, marine and terrestrial records remains difficult because terrestrial data based on pollen records, lacus- trine archives and cave sediments are often fragmen- tary (Guiter et al. 2003). Data from the periglacial terrestrial settings of central and northern Europe are especially sparse and a correlation is usually difficult. Existing palaeoclimatic reconstructions for central Europe are based mainly on pollen, loess and lake records. The climate during Marine Isotope Stage (MIS) 3 (60–27 ka) was intermediate between oceanic and continental, characterized by humid conditions and a vegetation of low shrub or subshrub tundra (Bos et al. 2001; Guiter et al. 2003). During MIS 2 (Late Pleniglacial, 27–15 ka) the temperatures decreased and arid conditions with strong winds prevailed (Bos et al. 2001; Guiter et al. 2003). The coldest period with polar desert conditions and scarce vegetation occurred c. 20 ka (Huijzer & Vandenberghe 1998; Guiter et al. 2003). Cryoturbation features such as ice-wedge casts within aeolian deposits indicate the presence of DOI 10.1111/bor.12021 © 2013 The Authors Boreas © 2013 The Boreas Collegium