Re‐interpretation of the Meikirch pollen record, Swiss Alpine Foreland, and implications for Middle Pleistocene chronostratigraphy

Abstract

The Meikirch drilling site in the Swiss Midlands north of Bern is re-interpreted using a combination of sedimentological logging, pollen analyses and luminescence dating. The sedimentary sequence comprises about 70 m of lacustrine deposits, overlain by about 39 m of coarse glacial outwash interpreted to represent at least two independent ice advances. Pollen analyses of the apparently complete limnic sequence reveal a basal late glacial period followed by three warm phases that are interrupted by two stadial periods (Meikirch complex). The warm periods were previously correlated with the Holsteinian and Eemian Interglacials. According to luminescence dating, and with consideration of evidence for Middle Pleistocene climate patterns at other central European sites, a correlation of the Meikirch complex with marine isotope stage (MIS) 7 is now proposed. If this correlation is correct, it implies the presence of three intervals with interglacial character during MIS 7. However, the late Middle Pleistocene vegetational features of the Meikirch complex show significant differences when compared with the pollen record from the Velay region, central France. Possible explanations for this discrepancy are distinct Middle Pleistocene patterns of atmospheric circulation over central Europe and a different distribution of vegetation refugia compared to the Eemian Interglacial and the Holocene.

Applying SAR-IRSL methodology for dating fine-grained sediments from Lake El’gygytgyn, north-eastern Siberia

“…Unfortunately, the scarcity of material did not allow to cross check the results of ICP-MS by high-resolution g-spectrometry leaving some uncertainty if the investigated sediment are in radioactive equilibrium. However, reports from previous studies have demonstrated that lacustrine sediment is apparently not affected by disequilibrium as long as contents of organic matter and primary carbonates are low, both originating from increased bioproductivity (Lang and Zolitschka, 2001;Thomas et al, 2003;Preusser et al, 2005). Since Lake El'gygytgyn shows relatively low contents of organic material it is unlikely that correct dose rate determination is affected by this problem.…”

<sup>10</sup>Be depth profiles in glacial sediments on the Swiss Plateau: deposition age, denudation and (pseudo-) inheritance

“…Attempts have been made recently to solve this controversy by applying 10 Be surface exposure dating on erratic boulders in the Jura Mountains by , yet with limited success, as the oldest dated boulders date into MIS 6 but are interpreted to have been deposited much earlier. Various novel dating techniques based on luminescence and cosmogenic nuclides have been applied to sediments in Meikirch (Preusser et al, 2005) and its vicinity (Dehnert et al, 2010), and these studies do suggest that the penultimate glaciation was more extensive than the LGM. In any case, the till at Niederbuchsiten does very likely not document the oldest extensive glaciation, because it overlies fluvioglacial sediments that were deposited after an even earlier glacial advance and the respective denudational event.…”

Distribution, geometry, age and origin of overdeepened valleys and basins in the Alps and their foreland

“…The major limitation of this approach, apart from methodological uncertainties, is limited experience in dating sediments older than 150 ka. Initial studies imply that the method may be used up to 250 ka (Preusser et al 2005;Preusser and Fiebig 2009), and possibly beyond. However, this will need to be validated by systematic methodological investigations.…”