Abstract
The continuing development of analytical methods for investigating sedimentary records calls for iterative re‐examination of existing data sets obtained on loess‐palaeosol sequences (LPS) as archives of palaeoenvironmental change. Here, we re‐investigate two LPS (Hecklingen, Zilly) in the northern Harz foreland, Germany, being of interest due to their proximity to the Scandinavian Ice Sheet (SIS) and the position between oceanic climatic influence further west and continental influence towards the east. First, we established new quartz OSL and polymineral IRSL chronologies. Both methods show concordant ages in the upper part of the Hecklingen profile (~20–40 ka), but in the lower part IRSL underestimates OSL ages by up to ~15 ka for the period 40–60 ka. Interpretations hence refer to the OSL data set. Second, we applied Bayesian age‐depth modelling to data sets from Hecklingen to resolve inversions in the original ages, also reducing averaged 1σ uncertainty by ~19% (OSL) and ~12% (IRSL). Modelled chronologies point out phases of increased (MIS 2, early MIS 3) and reduced (middle and late MIS 3) sedimentation, but interpretation of numerical rates is problematic because of intense erosion and slope wash particularly during MIS 3. Finally, previously obtained grain‐size data were re‐investigated by end member modelling analyses. Three fundamental grain‐size distributions (loadings) explain the measured data sets and offer information on intensity and – combined with modelled OSL ages – timing of geomorphic processes. We interpret the loadings to represent (i) primary loess accumulation, (ii) postdepositional pedogenesis and/or input of aeolian fine fractions, and (iii) input of coarse aeolian material and/or slope wash. The applied modelling tools facilitate detailed understanding of site‐formation through time, allowing us to correlate a strong peak in mean grain size at ~26–24 ka to the maximum extent of the SIS and increased influence of easterly winds.
Highlights
The continuing development of analytical methods for investigating sedimentary records calls for iterative reexamination of existing data sets obtained on loess-palaeosol sequences (LPS) as archives of palaeoenvironmental change
A preheat temperature of 220 °C was adopted for the dose recovery tests (DRT), which were successful with a dose reproducibility better than 2% for sample BT1534, while a slight tendency for dose underestimation becomes apparent for sample BT1537 (7% underestimation for 196.3 Gygiven dose)
We established new OSL and IRSL chronologies for two LPS (Hecklingen, Zilly) in the northern Harz foreland, which are of particular interest for palaeoenvironmental research due to their proximity to the maximum extent of the Scandinavian Ice Sheet (SIS)
Summary
The continuing development of analytical methods for investigating sedimentary records calls for iterative reexamination of existing data sets obtained on loess-palaeosol sequences (LPS) as archives of palaeoenvironmental change. Due to rain-shadow effects of the Harz Mountains the eastern part of the northern foreland only receives modern precipitation ≤500 mm a–1 (Do€ring 2004; Fig. 1) This small-scale gradient from an oceanic climate in the west to a continental one in the east offers the possibility to study the environmental effects of such variations for the past. While the Zilly profile preserves only Lateglacial loess, the LPS at Hecklingen encompasses a more continuous record back to MIS 3 at least (Reinecke 2006) This is in stark contrast to observations from Saxony, Poland and western Ukraine, indicating a strong erosional phase causing large depositional gaps in most places (e.g. between ~65 and ~35 ka; Jary & Ciszek 2013; Meszner et al 2013).
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