Sedimentary characteristics and spatial differentiations of the sedimentary facies in the Yellow River sub-delta lobes during the different historical periods

Abstract Frequent swings and diversions of old channels in lower reaches coexist with the multi-phase overlapping of Yellow River sub-delta lobes. In addition, sedimentary bodies of sub-delta lobes during various developmental stages are known to have undergone overlapping with one another. Experimental analyses of 24 short-column (length of less than 1 m) stations were examined. In addition, due to the influencing effects of swinging of old channels in the Yellow River’s lower reaches, sub-delta lobes of the different historical periods were in different evolution stages, including erosion and degradation(Diaokou), scouring and silting balance(Qingshuigou, and Shenxiangou sub-deltas), and sedimentation (current estuary sub-delta). The characteristics of sedimentary bodies, along with scouring and silting of the seabed, were found to have impacts on the sedimentary characteristics of the sub-delta lobes. The sedimentary bodies of the Yellow River Delta (YRD) were divided into three types, after cluster analysis had been completed. Type-I was dominated by the current estuary sub-delta. Their grain-size frequency distribution curves were with an average grain size of 4.43 φ , and characterized by moderate sorting, thus indicating that the sediment supply of the Yellow River was the main source, while a trend of sea continuously receiving the continental source supply and silt existed. The sand content of Type-II was significantly higher than that of type I, and its sand composition was greater than 40%. In addition, the frequency accumulation curves were either bimodal or multimodal, with poor sorting. The area was formed by severe erosion and transformation of the original sediment. The long-probability curve of Type-III area was mainly unimodal. The average grain size fluctuated at approximately 5.26 φ , with poor sorting, indicating that the sub-delta was in a process of development. The erosion accumulation processes were superimposed. The evolution models of the YRD since 1855 were successfully clarified, providing theoretical references for deposition processes in the YRD.