Grain-size distribution and magnetic susceptibility in Faiyum Depression sediments, Egypt and the implication for eolian activity

Abstract

The Faiyum Depression,a flood plain of the Nile downstream,receives sediments from the Nile and the Sahara Desert.By means of grain size and magnetic susceptibility analysis of sediments from core FYAM(4.6m deep),combined with surficial characteristic of quartz grains,occurrence of gypsum and carbonate contents,the paper is aiming to reveal some indicators for eolian activity in the Faiyum sediments.The results suggest that there are totally seven patterns of sediment grain-size distribution,including unimodal and biomodal patterns composed of a fine-grain peak(6-20μm) and a coarse-grain peak(80-100μm).These patterns have a close relation to magnetic susceptibility except for the sediments of two layers with high or low magnetic susceptibility caused probably by human activity and carbonate content.When the coarse-grain peak appears as a major pattern,the sediments are characterized by low magnetic susceptibilities,implying eolian quartz content increased,and strong sandstorms.When the fine-grain peak is dominated,the sediments were consistent with high magnetic susceptibility and less eolian quartz grains,probably revealing increasing sediment supply from the Nile.