Anisotropy of Magnetic Susceptibility (ASM) as a powerful tool to study sedimentary process in continental basin

Syn-orogenic sedimentary accumulations provide long, continuous and detailed records of both tectonic and climate changes ongoing during mountain building. Deciphering these two end-member processes from sedimentary records remains challenging but of primary importance to understand how tectonics and climate interact. This is of particular relevance in continental area where detailed age control and environmental data are often lacking due to the absence of abundant good biostratigraphic records. Here, we present high resolution measurements of Anisotropy of Magnetic Susceptibility (AMS) combined with sedimentological analyses in three Neogene sections located in the Junggar and Tarim basins at edges of Tianshan ranges. In these sections we observed that AMS magnetic parameter changes are strongly correlated to important sedimentary environmental variation or sedimentation rate changes. We found that the AMS shape parameter T can provide information related to the hydrologic regime and transport conditions experienced by sediments. Indeed, we believe that T is sensitive to a preferred orientation of the particles acquiring during deposition or to the particle shapes themselves. The magnetic susceptibility is mainly related to the concentration of magnetite in sediment and may reflect potential changes in source or indicate environmental and climatic changes. This study shows that AMS analyses of continental sediments can be a powerful tool to document environmental changes as it provide high resolution records that are complementary to classic sedimentology.