Magnetic properties of sediments from major rivers, aeolian dust, loess soil and desert in China

Abstract

The continent of China delivers huge terrigenous sediments to the East Asian marginal seas and northwest Pacific Ocean by riverine and aeolian inputs, which exerts a great impact on marine sedimentation, primary productivity and biogeochemical cycle. In this study, magnetic properties of the sediments from the Changjiang and Huanghe river systems were investigated, in order to provide potential provenance tracers. Besides, the top soil from the Loess Plateau, Taklimakan desert sand and dust storm particles were comparatively studied to reveal the controls of magnetic properties in various depositional environments. The Changjiang sediment is characterized by the highest concentration of magnetic minerals and the largest variations for most magnetic parameters, while the Huanghe sediment has much lower content of magnetic minerals. The loess soil sediment yields the highest frequency-dependent susceptibility χ fd%, while the aeolian dust has similar magnetic susceptibility but higher saturation isothermal remnant magnetization and lower anhysteretic remnant magnetization χ ARM. The desert sand has the lowest values of all magnetic parameters, indicating the lowest ferrimagnetic mineral concentration with coarser grain size. The magnetic properties of the Changjiang sediments are primarily determined by the diversity of lithology in its large drainage basin, while the sediment grain size basically accounts for the variation of magnetic parameters in the Huanghe sediment. The gradual increase of χ fd% towards the lower reaches suggests it may potentially indicate grain size fractionation in the catchments. Although some magnetic parameters can apparently discriminate the origins of fluvial and aeolian sediments, reliable magnetic proxy for distinguishing sediment origins in marine environment can only be established if hydrodynamic differentiation and post-depositional diagenetic alteration of magnetic minerals are fully understood.