Magnetic properties of sediments from the Pangani River Basin,Tanzania: Influence of lithology and particle size

Abstract

Use of magnetic properties in tracing sediment source in river systems is valuable for proper management of soilerosion and dam siltation. This study investigated magnetic properties variation from the upstream down to thecoast of the Pangani River Basin in Tanzania, East Africa. The influence of lithology and sedimentary sorting onmagnetic properties from source to sink pathway has been discussed. Results show that lithology can explainthe differences in magnetic properties among the tributaries in the upstream and in the lower reach of themain stream. Ferrimagnetic minerals mainly consist of magnetite and titanomagnetite, with the latter moreabundant in the upstream tributary Kikuletwa River. Upstream sediments have higher ferrimagnetic mineralconcentrations but coarser grain size than the mainstream sediments, especially the dam sediments. A declinein ferrimagnetic mineral concentration withfining grain size is also observed along the mainstream. Such atrend can be explained by hydrodynamic sorting effect, which is well documented elsewhere. This study demon-strates that lithology and sorting have strong effect on magnetic properties, which should be properly addressedwhen using magnetic method in assessingfluvial sediment source