The New Finding of Paleozoic Devonian Fossils in Pyongnam Basin,Korean Peninsula and Its Geological Significance

Pyongnam basin is located in the Central of the Korean Peninsula,Sino-Korean platform.In the Pyongnam basin,Paleozoic strata are well exposed,especially the Cambrian to Silurian System in the middle-southern basin.However,the Upper Ordovician to Lower Carboniferous strata and fossils had not been found in other districts of Pyongnam basin except for the Upper Ordovician to Silurian strata in Goksan and Pobdong region.Recently,in the Pyongyang district,the central of Pyongnam basin,several fossils was newly found from the upper part of Middle Ordovician Series(Mandal Formation) such as Chaetetes cf.nantanensis,Calceola sp.,Thamnopora sp.,Cladopora sp.and so on.These fossils are identified as the Devonian in age.The fossiliferous bed extends 2-3 km.The studies of these fossils suggest that it is possible that the upper part of the Mandal Formation could be Devonian System.In the Sino-Korean platform,except for the western and the southwestern,most parts are lack of the Middle Ordovician to Lower Carboniferous Series,only the Benxi Formation's geological age was recognized as the Early-Late Carboniferous.Most of the Devonian and Early Carboniferous fossils were found in the eastern part of the Sino-Korean platform.It is shows the geotectonic evolution of Paleozoic in the eastern Platform has a different tectonic setting from the western part.This scientific discovery gives a new concept about the paleogeography and geotectonic evolution in the Sino-Korean platform.