The Relationship Between Fluvial Terraces Of Daju Basin And Pleistocene Glaciations In The Yulong Mount

Yulong Snow Mountain (5596m) existed four glaciation in Pleistocene, Kunlun glacialperiod, Reciprocal third glacial period, the Penultimate Glaciation, the last glacial. Themoraine and fluviological deposit were deposited in Daju Basin at the northern part of YulongSnow Mountain. The Jinsha River rushed out of the barrier which builded by Yulong andHaba Snow Mountain then flowed into Daju Basin and formed river terrace. Through fieldinvestigation and data analysis, the geochemical characteristics of elements analysis shows:1)each sediment sample percentage differences of chemical composition, there are variations intheir differences. The first and second terrace of the chemical composition is main of SiO2,Al2O3, both the content are over55%. Enrichment of SiO2, Al2O3indicates a relatively highenvironment temperature. Fe2O3content in the sample close to the loess Fe2O3content in theproof sample shows that oxidation degree is not high, speculates that the ancient environmentsimilar to the loess formed relatively dry environment.2) Samples by measured in the studyarea, sa values were greater than4in addition to the DJ–9, and other geochemical parametersalso show terrace formed the ancient environment is relatively dry. Sa and saf value have thesame change trend, the sa value increase with the saf value increased.3) from the losscoefficient, weathering eluvial coefficient ratio, magnesium aluminum multiple indicators cansee terraces formed climate, cool-dry degree from high to low in turn for: T4> T3> T2> T1.The following conclusions based on magnetic susceptibility studies:1) different levels ofterraces of magnetic susceptibility values of Daju Basin change obviously, the farther thedistance from the level of the Jinsha River, the higher the altitude, the smaller the magneticsusceptibility, the climate is drier.2) by comparing different types of sediment susceptibility,found the changes scope since the quaternary sediments of magnetic susceptibility: glacialtill> glacial lake> loess> lake, Daju Basin of sediment susceptibility values in23-175(10-8m3. Kg-1), close to the loess magnetic susceptibility distribution range, change small.Comprehensive study terrace series, height, age and yulong snow mountain ice age, getthe following conclusion: (1) Based on the analysis of geochemical elements and magnetic susceptibility in thestudy area, it indicates terrace formed at all levels of the ancient environment generally dryand cold, and the level differences. Combining with field survey of landscape, Daju basinquaternary terraces internal development, the altitudes are1650m,1700m,1740m and1780m. According to the system data analysis of the formation of terrace, Daju basin terrace of theterrace is other quaternary sediments as "rock" in the common influence of tectonicmovement and climate formation eroded terrace, river terrace series is less than the climate-interglacial stage cycle, the development mode for the "accumulation of ice age, interglacialincised" and " glacial interglacial stage transition incised, glacial accumulated".(2) T1、T2、T3、T4terraces correspond to deep sea oxygen isotope MIS1、MIS2、MIS8-6、MIS18-16stage in the Daju basin of Jinsha River. The forming age is Holocene Age,the last glacial age, Zhonglianggan ice age and Kunlun ice age. There is good correspondencebetween the Daju basin terrace series and Yulong Snow Mountain ice age series.(3) The Holocene river terraces calculated incised rate must be greater than rivers ofincised rate for a long time, and it can’t simply use the Holocene river incised rate measuremountain uplift.