Post-Depositional History of Western European Loess Deposits from Magnetic Anisotropy

Abstract:

The ability of loess deposits to record millennial-scale climate change is widely known, especially via the use of rock/environmental magnetism. To grasp the true mechanisms for these changes and to identify both local and wider-scale variations, in-depth studies into these terrestrial deposits will continue to be undertaken. Using the well-researched Nussloch loess-palaeosol deposits in Germany, we provide insight into the depositional and post-depositional processes that occurred during the Last Glacial period via an anisotropy of magnetic susceptibility (AMS) study. Post-depositional deformation is identified within several depth intervals that are defined by: prolate orientation population distributions, scattering of the principal susceptibility axes and where a dipping foliation plane is observed. This magnetic fabric is associated with gleying-induced processes and the initiation of gelifluction. Any intervals with a primary aeolian fabric show no evidence of a preferred orientation in the maximum susceptibility axes of the AMS ellipsoid. Furthermore, soil-forming processes did not appear to play an important role in modifying the parent loess fabric, suggesting only weak pedogenesis occurred. In addition to the Nussloch sequence, AMS on a targeted depth range from a profile in Achenheim, France, is presented to decipher the depositional and post-depositional fabrics in Western European loess on both sides of the Rhine valley.