Study On Grain Size Characteristics Of Sediments From Different Marine Environments

Sediment grain size is one of the important indexes of marine sediment analysis.Through the analysis of sediment grain size,it can judge the nature and energy condition of the transport medium,clarify the transport mode and the sedimentary form,distinguish the type of deposition,and then reduce the sedimentary power,climate and environmental information,and provide the basis for the determination of sedimentary facies and sedimentary environment.In this paper,the typical sections,namely the coastal zone,the continental shelf,the semi-deep sea and the deep sea sediments,are selected for the analysis of the grain size component,grain size parameter,grain size characteristics to reveal the response characteristics of sediment grain size in different depth.Based on the detailed analysis of sedimentation dynamics and environment,the influence mechanism of grain size characteristics of different depositional environments is discussed through the comparison of grain size characteristics of different depth.The main conclusions are as follows:1.The average grain size of sediments in the south coastline of Laizhou Bay is 3.2 ~ 7.4Φ,most of them are silty sand and silt and the sorting is poor.Sediment samples are scattered in the C-M plot,and the transport mode is mainly evenly suspension and variable suspension.The increase of the average grain size is mainly controlled by the medium-coarse grained components.In the scatter plot of the skewness and sorting values,the cast points scattered.It shows obvious segmentation in the scatter plot of sorting value and average grain size.The analysis of grain size characteristics shows that the area is affected by both river and ocean,and has experienced many transgressions during the geological history,and manifested as fluvial facies and delta facies.2.The average grain size of sediments on Huanghai shelf is between 4.1 and 5.6Φ,which is silty sand and sandy silt and the sorting is poor.The sediment sample is concentrated in the C-M,and the transport mode is obviously variable suspension.The increase of the average grain size is mainly controlled by the medium-coarse grained components.In the skewness-sorting value scatter plot,the cast points scattered and show an unobvious negative correlation.It shows a obvious positive correlation in the sorting value-average grain size scatter plot.The grain size characteristics indicate that the study area is in a relatively high energy stability sedimentary environment and is influenced by the coastal flow of Shandong Peninsula,and the hydrodynamic environment is strong.3.The average grain size of the semi-deep sea sediments in the Okinawa Trough is between 4.8 and 7.0 Φ,which is clayey silt and sandy silt and sorting is poor.Sediment samples are dispersed in the C-M plot,the transport mode is evenly suspended.The increase of the average grain size is mainly controlled by the mediumcoarse grained components.In the skewness-sorting value scatter plot,the cast points scattered and there is no significant correlation.The sorting value-the average grain size scatter plot shows a significant segmentation.The grain size characteristics indicate that the sedimentary environment is relatively stable in the study area,and no major changes have occurred in the sedimentary environment.There are only small fluctuations in the individual horizons.The source of the material is multiple and the hydrodynamic conditions are strong and controlled by the Kuroshio in the later period of deposition.4.The average grain size of the deep sea sediments in the southwest Indian Ocean Ridge is between 7.1 and 8.5 Φ,and the content of clayey silt and silty clay is equivalent.The sorting is poor.The sediment sample is concentrated in the C-M plot,and the transport mode is oceanic sedimentation.The increase of the average grain size is mainly controlled by the fine grain components.The cast point is concentrated and shows obvious negative correlation in the skewness-sorting value scatter plot.In the sorting value-the average grain size scatter plot,it is relatively scattered and shows a negative correlation.The grain size characteristics indicate that the study area is in a relatively low-energy stable hydrodynamic environment.The sediments are less affected by the later stage,and the hydrodynamic conditions affected by the Antarctic bottom water have little change and only fluctuate in a small range.5.There are significant differences in the grain size characteristics of clastic sediments in different seas.As the depth of the study area increases,the average grain size,variation range,clay content,sand content,grain size composition and grain size parameter of the sediment sample varying with the drilling depth,the control component and skewness of the average grain size shows a certain trend of change.The cast area and concentration degree of the sedimentary samples in the Shepard triangular figure,C-M diagram and granularity structure scatter plot is distinctly different in different seas.And the sorting value and kurtosis of clastic sediment samples in different sea areas are generally similar.For the same sea area,the grain size characteristics of the sediment samples are also different in different study areas when the water depth conditions are roughly the same,including the sediment name,the cast area in the C-M plot,the sediment transport mode,the cast point of the grain size scatter plot and so on are significantly different.