| Huguangyan Maar Lake is an enclosed lake,whose high resolution sediment records,is a sensitive indicator of paleoclimate and paleoenvironmental changes.It can be a complete record of regional vegetation,human activities and succession of the environmental climate during geologic history.Unopened to the outside,Huguangyan Maar Lake has a relatively simple hydrodynamic environment,making it a convenience to research and application of sediment trends analysis.In this study,with the surface sediment and suspended matter from Huguangyan Maar Lake as the researched objects,sedimentation characteristics and its depositional dynamic environments was studied.The main research contents are as follows:1.Using the grain size of sediment,the sediment types and the distribution characteristics of surface sediment are studied.2.The main sources of sediments were studied by the analysis of sensitive grain size components.Based on the analysis of grain size trend,the sediment transport trends and sedimentary environment characteristics of Huguangyan Maar Lake were studied.Based on the analysis of total organic carbon(TOC)and Loss on Ignition(LOI)in sediments,the distribution of organic matter content are studied.3.Based on the distribution of suspended grain size and concentration of water in Huguangyan Maar Lake,the hydrodynamic environment are studied.The main conclusions are as follows:1.Huguangyan Maar Lake surface sediments are mainly composed of four types of clastics,including mud,silt,sandy silt and silty sand.Among them,silt and mud take up the majority,which are the main sediment type;sandy silt and silty sand are distributed close to inshore region and take up minority.These samples average grain size range from 2.1 to 7.5?,with an average value of 6.8 ?.Generally,the grain size of sediment samples becomes finer with increasing of the water depth.However,near the inshore region,the grain size parameter changes dramatically due to the rain wash the shore into the lake.It appears estuarine deposit trend.The deepest of lake,which is close to the lakeshore and volcanic rock wall,is not the place of existing the most fine sediments region.There are four obviously peaks in frequency curves of the sediments of Huguangyan Maar Lake.Those indicate fine particles transported far away still had a large effect on the size fraction of sediments.2.Total organic carbon(TOC)content of surface sediments range from 0.07%~4.83%,with an average value of 1.88%,higher than other lakes and waters,which indicates the higher productivity.TOC content of sediments increase with increasing of the water depth,showing the increasing of the water depth as well as the decrease of oxygen content in water are beneficial to the preservation of organic carbon.The value of LOI550 of surface sediments range from 4.87%~18.17%,with an average value of 13.64%.The value of LOI550 has a good correlation with TOC and organic matter content.3.Grain size trend analysis,was used to study the lake surface sediment particle size of rock geochemical parameters,such as distribution characteristics of the dynamic mechanism of formation,which indicates its weak hydrodynamic environment.However,the suspended grain size of the surface and bottom of water becomes coarser indistinctively with increasing of the water depth.One likely reason is that the strong wind-wave disturbance action in the coastal lead to the resuspension of sediments,and those main part is fine grain size matter. |
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