Magnetostratigraphic framework and magnetic properties of modern sediment in the Yellow River Delta

Magnetostratigraphic and rock magnetic studies have been conducted on sediments Core Z07 from the Yellow River Delta. Constrained by the deposition rate and paleomagnetic secular variation curves, we constructed a reliable chronological framework. Rock magnetic results indicate that the main magnetic minerals are single domain (SD) magnetites with considerable amount of superparamgnetic (SP) particles. The grain size and concentration of magnetic particles in sediments change significantly with depths. Compared to the bottom sediment, the uppermost part has lower concentrations of SP and SD ferrimagnetic grains. We attribute these changes occurred around 2003 mainly to the Water and Sediment Regulation Scheme (WSRS) project launched by the Chinese government, which focuses on solving the sedimentation reservoir problems at the lower reaches of the Yellow River. Along with the continuous implementations of WSRS, the erosion rate of lower reach of the Yellow River increased. It became a new sediment source and the median grain size of suspended sediment in Lijin station increased accordingly, which results in elevated sediment loads. Therefore, this new source of sediment may cause the differences of magnetic properties around 2003.