Pliocene Ostracoda Assemblage And Its Palaeoecological Significance In Dongping Area,Qaidam Basin

The paper relies on the project of Qinghai Oilfield"Cenozoic Paleoecology and Petroleum Geology Research of Dongping Region Qaidam basin",to study Cenozoic ostracods biostratigraphy,paleoecology and palaeoenvironment in Qaidam basin.Obtain the following achievements and understandings:1.biostratigraphic studies.According to the analysis of 16 wells ostracods fossils in Dongping area of Qaidam basin,it can be identified 24 generals and 46 species.According to fossil natural output layers,species diversity and richness to established 6 ostracods assemblages and 2 vice assemblages,and make comparison with ostracods assemblages of other regions in Qaidam basin in Cenozoic,and discussed its significance.Bottom-up as follows:(1)Candoniella-Microlimnocypthere reticulata-Ilyocypris Assemblage outputs at Lulehe Formation,Era in middle,late Eocene.(2)Austrocypris-Cyprinotus(Cyprinotus)Assemblage outputs at lower Ganchaigou Formation,Era in Oligocene.a.Austrocypris levis-Ilyocypris errabundis Vice-Assemblage outputs at Lower member of lower Ganchaigou Formation,Era in early Oligocene.b.Cyprinotus(Cyprinotus)-Subulacypris Vice-Assemblage outputs at upper member of lower Ganchaigou Formation,Era in middle,late Oligocene.(3)Hemicyprinotus-Mediocypris Assemblage outputs at upper Ganchaigou Formation,Era in early Miocene.(4)Qaidamocythere-Youshashania Assemblage outputs at lower Youshashan Formation,Era in middle,late Miocene.(5)Cyprideis littoralis-Cyprideis subeboliangensis-Eucypris honggouziensis Assemblage outputs at upper Youshashan Formation,Era in early Pliocene.(6)Leucocythere-Microlimnocythere reticulata-Ilyocyoris Assemblage outputs at Shizigou Formation,Era in late Pliocene.2.Community paleoecology.According to the characteristics of fossils buried,species diversity,richness and natural combination,it can be divided into some communities,and analyzed the changes of community composition,to investigate the main factors influences environment of community.The main factors influences ostracods community are salinity,water temperature,water depth and basement properties or ostracods ecotypes.3.According to internal succession and community replacement,and the relationship between the changes of the ostracods species and changes in different stages of base-level cycle,to determine trends of lake level changes,and explore the relationships of ostracods community succession,replacing and sequence stratigraphy.