Biostratigraphy And Palaeoecological Characteristics Of Fossil Ostracod From The CCSD-SK-Ⅰ(South) Borehole, Songliao Basin

"China Cretaceous Continental Scientific Drilling Project: SK-â… "(CCSD- SK-â… ) which prompted by the concern among Chinese scientists over"Major Geological Events and Greenhouse Climate Change in the Cretaceous Earth Surface System"was the first scientific drilling of continental cretaceous strata all the world, and attracted all the global palaeontology and paleoenvironment scientists to focus on Songliao Basin, Northeast China. Basis on the 944.23m continuous, high-resolution drilling core, we study the biostratigraphy and palaeoecological characteristics of fossil ostracod from the south borehole.Basis on a detailed study of ostracod specimens, more than 80 species of 13 genera have been identified, and 15 fossil assemblages have been established, detailed ostracod biostratigraphic framework for CCSD-SK-â… (south) borehole has been established, and ostracod biostratigraphic correlations from Quantou Formation to Nenjiang Formation of Songliao Basin are discussed. Biostratigraphic relationships between ostracod, dinoflagellates and sporopollen has also been discussed.This paper carried out detailed study of palaeoecological characteristics of ostracod from the south borehole, including statistics fossil abundance, simple diversity, double valve shell/univalve shell ratio, complex diversity, describe characteristics of the fossil preservation, etc.). Basis on those detailed palaeoecological characteristics information, system analysis and discussion of palaeoenvironment (including water depth, salinity, hydrodynamic conditions, oxygen content, etc.) and palaeoclimate evolution in Songliao Basin has been taken.The available data of ostracod rangs for the Quantou Formation to Nenjiang Formation of Songliao Basin were examined and combined with new data from CCSD-SK-â… (south) borehole. A cumulative species diversity curve is presented for the ostracod of the Late Cretaceous of Songliao Basin. We consider that low diversity associated with a deeper water environment, high diversity corresponding with a lake-regressive trough on a long-term regressive. Basis on those data and curve, a model for lacustrine level change of Songliao Basin in early Late Cretadeous has been proposed.