| The Yellow River is the second river of China, with world-famous of its high sediment-laden water. The Yellow River Deltal is located in the transitional zone of the rivev-sea interaction, where land and sea interact tensely. This area not only is the sink of the materials from the Yellow River into the sea, but also the source of the Yellow River material dispersal system into the BohaiSea. With the sharp decrease of sediment supply from the Yellow River, marine dynamics have become more dominant in reshaping coastal topography along the subaerial Delta of the Yellow River. During recent years, some parts of coasts have undergone notable erosion. The impacts of human activities on the sediment load of the Yellow River and the long term evolution of the delta have been extensively investigated. This dissertation presents a data-based study of surface sediments coverd large area and measured sample columns, by applying geostatistics analysis, grain size trend analysis and GIS techniques to investigate the spatial distribution and transport pathway of the sediment, and the grain size response to the drastic decrease riverine sediment discharge.By using geostatistic analysis, this study reveals the spatial correlation of the clay and sand fractions are notable, with the spatial correlation scale being44km and39km, respectively, while the spatial correlation of silt is moderate. The anisotropy of the sediment components is clear at the scale<20km and>60km. The distribution of the depocenters of sand fraction is very heterogeneous; the boundary between these sedimentary units and their substratum is very sharp.The data of surface sediment samples collected from the littoral area of the Yellow River delta in2000and2007are used to investigate the spatial distributions and movement of the sediment by applying the grain size trend analysis model of Gao and Collins (1994, Journal of Coastal Research,10(1),70-78). In order to ensure that the model is applied rigorously it is proposed based on the geostatisctic method to determine the characteristic distance (Dc) using the mean range value with the minimum standard deviation of grain size parameters. The data and analysis show that in the littoral area as a whole the sediments in the erosion area and inshore area are coarser than that in the accretion area and the offshore area, which clearly indicates the important role played by the hydrodynamic processes in lateral sorting of sediments. The grain size trend analysis reveals two converging zone of sediment and a sediment coarsening trend from2000to2007. Possible mechanisms for these are discussed.The mean range value with the minimum standard deviation gives the best representation of Dc. This ensures that the range values are relatively independent to different interpolation distance, which means the range value could response the spatial autocorrelation between samples regardless of the interpolation distance.The sediment types in the Yellow River delta are sand, silty sand, sandy silt, sandy mud, silt and clay. Sandy silt is most widely found in the study area. The grain size of sediments in the study area shows a seaward fining trend. In the shallower region, spatial variations in surface sediment size are large and strongly influenced by waves through sediment re-suspension processes. Sediment in2007was overall coarser than that in2000most probably due to the erosion of the subaqueous delta after the drastic decrease in riverine sediment supply.According to variation characteristics of grain size parameters and combining with dating by AMS14C, it is revealed that, from top to bottom, the sedimentary facies in the Yellow River Delta has experienced floodplain facies, river facies, delta-front facies, neritic facies, tidal flat facies and river facies in sequence. The Flemming ternary diagram proves the theory about the sedimentary dynamical environment had exhibited variation process of strong (terrestrial facies)-weak (marine facies)-strong (terrestrial facies) is reasonable.
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