Non-magnetic indicators of pedogenesis related to loess magnetic enhancement and depletion: Examples from the Czech Republic and southern Siberia

Abstract

We carried out a multiparameter investigation for non-magnetic proxies of the intensity of pedogenesis in loess/paleosol sections from two different climate settings, Dolní Věstonice, central Europe, and Krasnogorskoye, southern Siberia. The work was performed in order to clarify the problem of two opposite scenarios of magnetic susceptibility (MS) patterns in these two profiles, the “Chinese” model with magnetically enhanced paleosols and the “Siberian/Alaskan” model with magnetically depleted paleosols. The age constraints on the Krasnogorskoye section were inferred from an independent correlation with the well-dated Dolní Věstonice section, based on MS and sediment color (CIE L ∗ ), and with the MS log from Lake Baikal. The pedologic description of the loess/paleosol sections and their correlation was considerably improved by the use of Vis spectral proxies (CIE L ∗ , reflectance in the red band); their weathering intensity can be effectively characterized by diffuse reflectance spectroscopy (DRS) and geochemical (CEC and Rb/Sr) proxies. Whereas the MS is strongly dependent on the type of soil (chernozems vs. brown soils), the geochemical proxies, in particular CEC, proved to be relatively independent of the soil type. These parameters are less affected by region-specific conditions than the MS signal. The non-magnetic proxies indicate relatively dissimilar climatic trends at the two sites during the last glacial–interglacial cycle. A long-distance correlation, based solely on the MS signal, can be adversely affected by switching between the Chinese and the Siberian/Alaskan magnetic modes, this having been observed at the Krasnogorskoye section. In general, no single universal proxy of weathering or pedogenesis intensity would be applicable across broad regions or considerable climatic gradients. Paleoclimatologic interpretations of large regions should always be based on a carefully designed, multi-proxy approach.