Abstract: There are some important ecological reserves and oil exploitations in modern Yellow River delta, which located at the junction of sea and land. Influenced by rivers, currents and human activities, the modern Yellow River delta has a complex composition of sediment grain size and sources. A total of 219 sediment samples from the Yellow River delta were collected in this paper. Firstly, the grain size distribution and material source of the modern Yellow River delta sediment were analyzed by particle size analysis method. Then the parametric endmember model analysis method was used to divide the material sources of sediments. Finally, the cluster analysis method was used to analyze the surface sediment types. The results show that the grain size composition of delta sediments is mainly silt (71.10%) and sand (27.62%), most of the sediments are of medium grain size sorted and the curve of the grain size distribution is nearly symmetrical. The delta sediments can be divided into three types of end-mumber such as EM1, EM2 and EM3, which represent three different material sources. Among them, EM1 is from fluvial sediments, EM2 is from tidal current sediments and EM3 is from the current Yellow River fluvial sediments. According to the results of cluster analysis, the Yellow River delta is divided into three types of sedimentary environments. The first type is mainly distributed in the middle and upper reaches of western part of the Yellow River delta rivers, including Maxin River, Zhanli River, Caoqiaogou River and Tiaohe River, which is mainly deposited by old river with weak hydrodynamic force. The second type is mainly distributed in the eastern part of rivers such as Diaokou River, Shenxiangou and the current Yellow River (Qingshuigou), and the current Yellow River has strong sedimentary dynamics. The third type is mainly distributed along the northern coast and tidal flat of the Yellow River delta, which is strongly affected by the marine tidal and the coastline is eroded. In addition, human activities also had a certain impact on the changes of the coastline in the Yellow River delta.

Key words: Yellow River delta, surface sediments, grain size, end mumber, source analysis