Paleoenvironmental signatures of aeolian and fluvial sedimentary end-members off NW Africa

Abstract

This thesis presents a new approach to characterize properties of terrigenous sediments deposited off subtropical Africa. Grain-size distributions, geochemical compositions, and magnetic parameters of core material off the Gambia and Senegal rivers were analyzed. By end-member (EM) unmixing and least-square fitting, mixing coefficients and multi-parameters properties of fluvial and aeolian fractions were obtained. The properties are influenced by different factors and the joint characterization enables a three-level interpretation: (1) Grain-sizes reflect transport energy. (2) Geochemical composition differs in fluvial and aeolian sediments. (3) Magnetic mineralogy mirrors weathering and environmental conditions in the source areas. Volumetric EM representations enable to budget fluxes of aeolian and fluvial material. The highest dust accumulation occurred during Heinrich Stadial 1 and corresponds to a 100 times higher flux with respect to today. Such high values have not been reported yet off NW Africa and emphasize that disturbances of the meridional overturning circulation cause dramatic environmental changes also in low-latitudes.