Cenozoic Sedimentary Characteristics And Provenance Analysis In Eastern Qaidam Basin

This paper is studying Cenozoic formation of Eastern Qaidam Basin in northernQinghai-Tibet Plateau. Choose Dahonggou and Huaitoutala section which has betteroutcrop, successive sedimentation and high-precision chronostratigraphy control toanalyze sedimentary facies and provenance. The main purpose is provenance analyses,start from the standpoint of sedimentary basin analyses, using clastic constituentmethod to analyze the provenance in detail and systemic. Identify the tectonic eventsand its time.At the same time, In a larger area, Compared with Dahonggou section inthe east Qaidam Basin and Huaitoutala section in Delingha Basin, Conclusions are asfollows:(1)According to lithology analysis, characteristics of lithofacies combination andthin-section identification, analyzing the sedimentary facies. The main sedimentaryfacies of Dahonggou section in study area are alluvial fan, fan delta, lacustrine, deltaand braided river facies. The main sedimentary facies of Huaitoutala section in studyarea are lacustrine, delta and alluvial fan facies. This period may be a relatively dryperiod in the Qaidam Basin.(2)According to the sandstone detritalcomposition analysisofDahonggou sectionand the emergence stratumofPeripheral orogenic belt, During the deposition period ofLulehe Formation, Main detritus type is metamorphic detritus, sedimentary detritus issecondly, volcanic detritus is least,indicating that NanQilian Mountains was the mainsource area. During the deposition period of lulehe top Formation from xia youshashanbottom Formation, Main detritus type is sedimentary detritus, metamorphic detritus issecondly, magmatic detritus is least, indicating that NanQilian Mountains and Lvliangshan was the main source area. During the deposition period of xia youshashanbottom Formation from shang youshashan middle Formation, Main detritus type ismetamorphic detritus, sedimentary detritus is secondly, magmatic detritus is least,indicating that Lvliangshan and Near the mountain was the main source area.During thedeposition period of shang youshashan middle Formation from shizigou Formation,Main detritus type is sedimentary detritus, metamorphic detritus is secondly, volcanicdetritus is least, indicating that NanQilian Mountains was the main source area.(3) According to the sandstone detrital composition analysis of Huaitoutalasection section and the emergence stratum of Peripheral orogenic belt, During thedeposition period of xia youshashan Formation from shang youshashan middleFormation, Main detritus type is sedimentarydetritus, metamorphic detritus is secondly,volcanic detritus is least, indicating that NanQilian Mountains was the main source area.During the deposition period of shang youshashan middle Formation from shizigoubottom Formation, Main detritus type is sedimentary detritus, metamorphic detritus isdriblet, magmatic detritus is absence, indicating that NanQilian Mountains was themain source area.During the deposition period of shizigou bottom Formation fromshizigou middle Formation, Main detritus type is sedimentary detritus, metamorphicdetritus is secondly, volcanic detritus increase, indicating that Aimunikeshan and thesoutheast Mountains was the main source area.During the deposition period ofshizigoumiddle Formation from qigequan Formation, Main detritus type is sedimentarydetritus, in which limestone detritus is mainly, Extrusive detritus increase, indicatingthat Oulongbulukeshan and the nearby mountains was the main source area.(4) On the basis of detrital component vertical change in section, recognizing thefour significant changes, And correlation of strata with high precisions, these fourchanges reflects the qilian orogenic belt of tectonic uplift event four times, thecorresponding time were45.0Ma,22.5Ma,11.3Ma,8.0Ma,which was also reflectedin the sedimentary record in other parts of plateau, it provides strong evidence fornorthern plateau which exists many stage uplift process.(5) byprovenance transition oftwo goals section in the studyarea wecan inferthatQaidam Basin and Delingha Basin, in which two target section are located, wereUnified basin In the early, has begun to gradually separated by a series of mountainsbetween them in xiayoushashan period, Delingha Basin,which is a intermontane basin,is formed with its surrounding mountains gradually uplifting in the late.