朝鲜平南盆地泥盆纪化石的发现及其地质意义

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

平南盆地位于中朝地台东缘朝鲜半岛中部。平南盆地古生界比较发育,特别是盆地中南部地区发育寒武系、奥陶系和志留系,仅在盆地东南部谷山、法洞地区发现了晚奥陶世到志留纪的地层,其它地区末曾发现过晚奥陶世到早石炭世的地层。最近在平南盆地中部平壤之东原中奥陶统(晚达组)上部发现了Chaetetes cf.nantanensis,Calceolasp.,Thamnoporasp.,Cladoporasp.等指示泥盆纪的化石;该含化石层的走向延续性比较好,延伸长度2～3km。基于上述研究,认为原来的中奥陶统(晚达组)上部可能为泥盆系。在中朝地台,除了西缘和西南缘地区以外,大部分地区没有发现晚奥陶世—早石炭世的地层,只有辽东太子河流域本溪组的地质时代被认定为早石炭世晚期到晚石炭世早期。这些泥盆纪、早石炭世化石都发育在中朝地台东部,说明古生代时期中朝地台西部和东部沉积环境及构造演化有差别,因而对于中朝地台古生代古地理和构造演化需要重新认识。

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.