A Study On The Conodont Biostratigraphy Of The Ordovician In Nanpu Depression In Hebei Province

Twenty-five carbonate samples were collected from NANPU-288 (N288) and XI-2 (X2) in Nanpu Depression of Jidong Oilfield. After the acidization of these samples, conodonts can be found in 13 samples. Moreover, there are some trilobite spines in 3 samples, some brachiopod chips in 5 samples.Eleven species belong to 6 genus and 10 broken undecided species were identified, mostly include: Eoplacognathus suecicus, Tripodus changshanensis, Scolopodus nogamii, S. opimus, S. restrictus, S. bassleri, Paltodus? parvus, Aurilobodus aurilobus, Drepanodus streblus, Oistodus sp., Baltoniodus sp., Panderodus sp., Tripodus sp., Acodina sp., Gnathodus sp., Idiognathodus sp.. Based on the biostratigraphic research of the specimens, two conodont assemblage biozones and one conodont assemblage can be divided, in ascending order, they are: Scolopodus quadraplicatus-Scolopodus opimus assemblage zone in Yeli Formation of the Lower Ordovician, Eoplacognathus suecicus-Acontiodus? linxiensis assemblage zone at the Lower part of Lower Majiagou Formation of the Middle Ordovician, Drepanodus streblus-Acodina sp. assemblage at the Lower part of Fengfeng Formation of the Upper Ordovician. In this paper, Fengfeng Formation was divided in Well-X2 firstly. Some well intervals are hard to be divided into biozones, the biostratigraphical analysis is still carried out as well. The biostratigraphic correlation ship was built up between the research region and concerned domestic and oversea areas.The study matures the research of the precursors, it bases on the given data and enriches the research of biostratigraphy in Nanpu depression. Besides, the study details the correlation between Nanpu depression and South China, North China as well as North American Mid-continent . Furthermore, the correspondence of lithology and electric log with conodont data at the key intervals of Well X2 was built up, which stores some material for the further research on integrated stratigraphy of the Lower Paleozoic at the researched area.Based on the biostratigraphic correlation, more detailed subdivision and revision were carried out in the researched area. The study shows that the division of the Ordovician Formations based on lithology and electric log is lack of evidence of sossils.