The Ostracods, Stratigraphic Classification And Correlation Of The Nihewan Formation In The Drilling Core Qk Ⅰ From The Qianjiashawa, Yangyuan County, Hebei Province

After dealing and identification with the late Cenozoic ostracoda fossils in the QKⅠcore, and analyzing the character of distribution and assemblage zones of them, on the base of the extensive collection of the late Cenozoic ostracoda fossils data in Nihewan Basin, we made a systemic study on the the late Cenozoic stratigraphy of Nihewan Basin. The study provide new abundant lithostratigraphic and biostratigraphic information for Nihewan Basin.Based on analysis lithostratigraphic and the distribution and assemblage zones of ostracoda in the QKⅠcore,we can get the conclusion as follow:According to the lithostratigraphic character of the QKⅠcore, the author divided them into 2 formation, the first is belong to the Pliocene series, Shaxia Fm, the other is belong to the Pleistocene series Nihewanian Stage, Nihewan Fm.Based on the really fossils information of the QKⅠcore, we divided them into 3 ostracoda assemblage zones. From old to new(from bottom to top), they are theⅠostracoda assemblage zone, Potamocypris plana-Candoniella-Ilyocypris zone, which is belong to is belong to the Late Pliocene. TheⅡostracoda assemblage zone, Leucocythere-Ilyocypris-Candoniella zone, and theⅢostracoda assemblage zone, Leucocythere-Cytherissa-Limnocythere zone, which are belong to the Early Pleistocene.The character of lithostratigraphic and ostracoda assemblage zones can preferably reflect the changes of environment, water salinity and climate. Comprehensive study in the area of the predecessors and in the QKⅠcore, we preliminary discussed the change from the Neogene to Quaternary on the environment, paleography and climate. From bottom to top, the old lake waved overspreaded, the water salinity gradually increased and partly decreased, the climate change from warm and damp to dry and cold and partly waved.