Study On The Sedimentary Characteristics And Lithofacies Palaeogeography Of Devonian In Northeast China

In this paper, the sedimentary system framework of the Northeast China was builded by the observation and measurement of statigraphy section, and the identification and analysis of paleontology, combined with previous geological datas. The stratigraphy and biostratigraphy on the north of the Xilamulun suture zone and the east of the eastern longitude 115°have been cleared. Then, under the new statigraphic framework the sedimentary characteristic of all sedimentary province in northeast China was analysed, and the sedimentary system was founded. With the study of the stratigraphy, the sedimentary system and the tectonic movement, five lithofacies paleogeography mapping units were divided and drawed. Conclusion was obtained at last.First, under the direction of "Tectonic activity theory" thought, the tectonic evolution of northeast China from the late Proterozoic to late Paleozoic tectonic evolution was studied. The process of the tectonic evolution in study area was the formation process of Jia-Meng block, which merged by five small blocks. Jiamusi-Songnen-Xilinhot microplate subducted in to the Argun-Xing'an micro-plate, which located in northwest in Devonian. Secondly, the Devonian stratigraphy in the study area was multiply classfied and correlated combining with the Rock strata section and biostratigraphy data. Then, five five lithofacies paleogeography mapping units were ascertained combining with domestic and international chronostratigraphic. They are the Lochkovian-Pragian, Emsian, Eifelian, Givetian and Frasnian-Famennian. The sedimentary facies of the stratigraphy section were analysed on the basis of these periods, following the sedimentary facies map of the main section in study area. The Devonian sedimentary system was founded in Northeast China. These included the N-E toward Xingan sea deposition area throughout the whole Devonian(the mainly facies was neritic facies and littoral facies), Heilongong taphrogenictrough in early and middle Devonian (marine deposits), the clastic rock facies and carbonate platform facies in the southern epicontinental sea, the clastic rock facies and pyroclastic rocks facies in Mishan-Baoqing stratigraphic area. Lastly, five lithofacies paleogeography maps were completed. It was the first time that Devonian was divided into five mapping units to draw the lithofacies paleogeography maps.