Late Quaternary climate and environmental reconstruction based on leaf wax analyses in the loess sequence of Möhlin, Switzerland

Lorenz Wüthrich,Jana Zech,Roland Zech,Dorian Gaar,Sönke Szidat,Fatemeh Shajari,Marcel Bliedtner,Gary Salazar,Frank Preusser,Imke Kathrin Schäfer

doi:10.5194/egqsj-66-91-2017

Abstract

Abstract. We present the results of leaf wax analyses (long-chain n-alkanes) from the 6.8 m deep loess sequence of Möhlin, Switzerland, spanning the last ∼ 70 kyr. Leaf waxes are well preserved and occur in sufficient amounts only down to 0.4 m and below 1.8 m depth, so no paleoenvironmental reconstructions can be done for marine isotope stage (MIS) 2. Compound-specific δ2Hwax analyses yielded similar values for late MIS 3 compared to the uppermost samples, indicating that various effects (e.g., more negative values due to lower temperatures, more positive values due to an enriched moisture source) cancel each other out. A pronounced ∼ 30 ‰ shift towards more negative values probably reflects more humid conditions before ∼ 32 ka. Radiocarbon dating of the n-alkanes corroborates the stratigraphic integrity of leaf waxes and their potential for dating loess–paleosol sequences (LPS) back to ∼ 30 ka.

Highlights

Vast parts of Switzerland were repeatedly covered by glaciers (Graf, 2009)
According to luminescence dating (OSL and IR50), most of the loess was deposited during marine isotope stage (MIS) 2 and late MIS 3, while the lowermost part of the sequence probably dates back to MIS 4 (Gaar and Preusser, 2017)
Most samples from Möhlin are characterized by a dominance of odd, long-chain (> nC25) n-alkanes typical for leaf waxes; other compounds and an unresolved matrix complex occur in variable amounts (Fig. 2)

Summary

Introduction

Vast parts of Switzerland were repeatedly covered by glaciers (Graf, 2009). This explains the lack of widespread thick loess deposits as they exist, for example, in southeastern Germany, southeastern and eastern Europe (Haase et al, 2007). The jet nowadays mostly occurs in winter, when the air fills up the Swiss Plateau and overflows the eastern Jura Mountains. This results in a dry wind with a speed of up to 10 m s−1 (Schüepp, 1982; Müller, 2001; Gaar and Preusser, 2017). According to luminescence dating (OSL and IR50), most of the loess was deposited during marine isotope stage (MIS) 2 and late MIS 3, while the lowermost part of the sequence probably dates back to MIS 4 (Gaar and Preusser, 2017)

Methods

Results

Discussion

Conclusion