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

Monday, 15 December 2014
Samuel Neil Taylor and France Lagroix, Institut de Physique du Globe de Paris, Paris, France
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.