Glacially overdeepened valleys in the northern Alpine Foreland preserve Middle to Late Pleistocene sedimentary sequences that may serve as valuable archives for reconstructing past environmental changes in response to shifts in climate. This study presents a multidisciplinary analysis of two sediment cores from the overdeepened Wehntal Valley at Niederweningen in northern Switzerland, integrating sedimentological, palaeobotanical (pollen, plant macroremains) and malacological data as well as luminescence dating. The basal sediments of the cores consist of lacustrine silts deposited under cold climatic conditions, associated with a treeless landscape and later with pioneer birch woodland. Previous studies have reliably attributed these deposits to the Penultimate Glaciation, that is the equivalent of Marine Isotope Stage (MIS) 6. Overlying this unit, carbonate‐rich silts containing a rich suite of biological remains were identified for the first time in the Wehntal Valley. These deposits suggest sedimentation in a marshy wetland bordered by mature deciduous‐coniferous forest, which corresponds to the early‐middle Eemian (MIS 5e). Above this, silty and peaty sediments indicate alternating lacustrine and marshy conditions under a variable climate, with a predominantly coniferous woodland, during the Early Würmian (MIS 5d–5a). Subsequent cooling, corresponding to MIS 4, led to a return to lacustrine conditions and a more open landscape. This stratigraphical and palaeoenvironmental framework aligns with previous studies in the Niederweningen area, confirming that the ‘Lower Peat’ unit is of middle to late Eemian age, while the ‘Upper Peat’, which contains mammoth remains, dates to MIS 3. During late MIS 3 or early MIS 2, the valley‐bottom lake disappeared and was replaced by a modest stream network with slope deposits from the sides of the Wehntal Valley. Although this chronostratigraphical interpretation is strongly supported by the biological proxies, luminescence dating results are in partial contradiction. The luminescence ages from one core are in fairly good agreement with the proposed sequence, while those from the other suggest that most of the sequence corresponds to the Early Würmian (MIS 5d–5a) after c . 100 ka. Reconstructing this complex sequence has been complicated by significant erosive events linked to fluctuations in palaeolake levels that led to important sedimentary hiatuses.
Miocic et al. (Mon,) studied this question.