| Xiashu loess is important Quaternary layer in the south of China, but also thecarrier of ancient environmental information in China northern subtropical areas, It’srecord the major climatic events that occur throughout the middle and lower reachesof Yangtze River and the East China region since the Middle Pleistocene in China.It’sgreat significance to reveal the regional climate and environment change and itsrelationship with global change.Xiashu loess source is one of the important scientific issues of climate in Loessdisputes over a long period of time.Based on the Xiashu loess of the middle and lowerreaches of Yangtze River during the last glacial loess deposition and dust source areasamples (Loess Plateau, Jianghuai plain alluvium) analysis of composition andmineralogical characteristics of granularity, preliminary study the influence ofdeposition separation, chemical weathering on the north and south of China Loessmineral composition, and explore the relationship between the main material sourcesof the Xiashu loess and Jianghuai plain glacial environment arid. Mainly by thefollowing:1the last glacial Xiashu loess deposition average particle size in general6.2-7.12Φ (10-20μ m), mainly consists of fine sand (4-16μ m) and silt (16-32μ m).Distribution characteristics of particle size distribution curve presented in Shuangfeng,showing positive skewness distribution, the main peak in16-32μ m, the second peakis less than2μ m, poor depositing selected. Size frequency accumulation curve mostare three section, two section, the typical characteristics of loess and the Loess Plateauin north of similar, aeolian characteristics that Xiashu.2Xiashu loess of the last glacial period, down from the north to the south peakgradually to the coarse fine migration, fine-grained fraction increases gradually;probability cumulative grain size curves of intersection point to the fine fractionsmobile; average particle diameter and median grain size decreases southward. Thesecharacteristics of Xiashu loess granularity space changes in overall characteristicsduring the last glacial period is from north to south tapering law.3Display X ray diffraction, the last glacial Xiashu loess <20μm size samplemineral composition mainly consist of quartz, mica, feldspar;20-63μ m fractionsamples were mainly composed of mica, quartz and feldspar minerals. Xiashu loessand Loess Plateau during the last glacial period, there are big differences in the composition and content of minerals, mainly in the less content of Xiashu loess,chlorite, quartz, feldspar and content is higher, the content of chlorite, Xiashu loesssmall with the main experience of chemical weathering strong.4Effects of small wind and water separation effect on the same grain sizecomposition of minerals in sediments. The clay minerals of sediments in differentstudy areas in the sample composition effects of chemical weathering effects.Compared with other research areas, Xiashu loess high illite crystallinity index andthe k/p value indicates the Xiashu loess experienced relatively strong chemicalweathering, and the Xiashu loess area climate more warm about. Stable quartz,potassium feldspar, plagioclase, biotite could be used as the source of evidence.5Different research areas of stable mineral relative content than the display,extensive accumulation in the south areas of China Xiashu loess and there is nouniform source, alluvial plain area of Jianghuai loose sediment is the main source.6Xiashu loess material from the local alluvial plain of loose sediments indicatealluvial plain area of Jianghuai occurred drought.Middle Pleistocene interglacialperiod, due to reduced summer monsoon precipitation edge Haidong withdrawalcaused by factors such as continental climate, vegetation degradation, resulting inloose sediments exposed part of alluvial plain, the formation of Xiashu Loesssource.The stud y from the source point of view for understanding tropical north ofglacial interglacial climate change provides new evidence. |
PDF Full Text Request