New frontiers in the molecular based reconstruction of Quaternary paleovegetation from loess and paleosols

The reconstruction of paleovegetation from terrestrial sediments such as loess and paleosols represents a major, but still challenging task in Quaternary research. A significant methodological advance was the implementation of biomarker applications to terrestrial archives such as loess sequences and fossil soils. Essentially, the n-alkane approach has been widely applied within the last years to reconstruct changes in the paleoenvironment as for example regarding the relative abundance of woody species versus grasses from Quaternary terrestrial deposits. However, complex distribution patterns of leaf wax lipid homologues in plants and often little taxonomic specifity limit the use of n-alkyl series in paleoflora research. In this study, retene is introduced as a new molecular marker specifically for conifer derived organic matter to Quaternary loess - paleosol research. The ratio of retene to cadalene serves as a useful proxy for the relative contribution of conifers to the paleovegetation. Up to now these molecular markers have been mainly applied to coal research and marine sediments. Using samples from the Tumara site (Siberia), the added value of this new molecular approach for paleovegetation reconstruction also for loess and Quaternary fossil soils is demonstrated. The results of this pilot study confirm the presence of conifers during the penultimate glacial in NE-Siberia.