Isolation of the syndepositional magnetic susceptibility signals from loessic paleosols of China

Bulk magnetic susceptibility (MS) has been widely used to differentiate the loess and soil units, and acts as a useful proxy of the intensity of summer monsoon to reconstruct the paleoclimate on the Chinese Loess Plateau. Since soil development occurs not only at the actual ground surface but also to a greater depth, bulk MS is overprinted by the post-depositional pedogenesis and can only be regarded as representative of a time period, rather than a specific point in time. Therefore, the bulk MS record, as a naturally smoothed curve, can illustrate the low-frequency Milankovitch cycles, but may be unable to adequately resolve high-frequency sub-orbital climatic changes.Based on the pedosedimentary processes of soil formation, the Magnetic Susceptibility Variation (MSV) model is proposed to isolate the syndepositional enhancements of MS that may be directly linked to the climatic conditions of dust deposition. After an indirect test of the concept underlying the MSV model, using an atmospheric methane data set from Taylor Dome, Antarctica, we further verify the model directly from a loessic paleosol by the tentative correlation between the MSV record of Chinese loess at Luochuan profile and δ18O of the NGRIP ice core within the last interglacial period. Our results show that MSV model may improve our understanding of widely used MS proxy itself, and climate variation within the interglacial time periods.