Study On The Paleoceanographic Environment Of Rouzha Section In Nagaze,South Tibet

In order to conduct a fine study on the characteristics of the paleomarine sedimentary environment in the Langkazi area of southern Tibet,the stratigraphic sequence,lithology,stratigraphic age,sedimentary phases and sedimentary environment of the Zoza section stratigraphy were studied by regional survey,microscopic rock thin section identification,zircon U-Pb isotope dating and sedimentary geochemical elemental analysis,which are of great significance to reveal the characteristics of the paleomarine environment in the study area.The analysis results of characteristics of petrology shows that,the stratum rocks of the researching area mainly are terrestrial sources and detritus,clay,iron.The component of detritus is quartz,most of them are the 0.02-0.05 mm particle diameter silty sands,other parts of them are 0.05-0.25 mm particle diameter fine sands.Their shape always being angular,rounding medium,sorting good,elongating directional distribution,in quartz grain,we can see wavy undulating extinction.On the basis of characteristics of grain size changing and Si O2 volume in sediment,we can consider the J-K limiting time,the ancient sea environment in the researching area is changing from the Late Jurassic's coastal shallow sea environment to the Lower Cretaceous' s shallow-half deep sea environment.The analysis results of characteristics of chronology shows that,through zircon U-Pb isotope testing,the 9th rhyolitic-suspected rock,the 28 th dacite volcanic rock of the sample,we took the absolute age of 140.6±1.7Ma,137.3±1.3Ma,and infer that the location of J-K stratum in researching area is at the battle of sangxiu team.The deposition chemical elements analysis of the earth shows that,according to the chemical elements value characteristics of V/(V+Ni),?Ce,V/Cr,Ni/Co,U/Th,Cu/Zn,Al2O3/Mg O,K/Na during the period of deposition J-K limiting time of Langrouza section,the ancient sea environment was weak oxidation reduction environment,at that time,the depth of the sea was grow,the salinity was decreased,the deposition rate was slow,the water was pretty turbulence,the deep part of the sea has layered,which led to sub deep-deep sea deposition environment.Figure 22;Table 22;Reference 75...