Stratigraphycal Correlation of the Qingbaikou System and Establish of the Jinzhou System

In 1934 year,Qingbaikou System is established in Jixian County,Hebei Province,Northern China by professor Gao Zhen-xi et al.It is divided into the Xiamaling Formation of the lower part of Qingbaikou System and the Jingeryu Formation of the upper part of Qingbaikou System.In recent years,a zircon U-Pb SHRIMP age was obtained from the ash bed in the Xiamaling Formation in Northern China Plate,yielding a weighted mean 206Pb/238U age of 1368 土 12 Ma.Another zircon U-Pb age gained from the same formation in Zhaojiashan,Hebei Province,yielding similar age(weighted mean 206Pb/238U)1366 土 9 Ma.These ages do not support the tradition idea that the Xiamaling Formation belongs to Neoproterozoic.According to the facts mentioned above,the author suggested that tie Qingbaikou System is divided into the lower Xiamaling Formation of Mesoproterozoic and the upper Jingeryu Formation of Neoproterozoic.Therefore,the Qingbaikou System is disintegrated.According to the stromatolites with Linella-Gymnosolen-Katavia-Cuijiatunia-Ximincunella assemblage and using reported new U-Pb age(SHRIPM),the Jinxian Group may be correlated with Xiamaling Formation,yielding a weighted mean 206Pb/U238 of 1368 ~ 1370 Ma in Yanshan Mountain area.So Jinxian Group is possible promoted as a stratigraphical unit of the system level.It is named as Jinzhou System by the author,belonging to Late Mesoproterozoic in age(1400 ~1000 Ma or 1400 ~ 1200 Ma).The establish of Jinzhou System is important significance in subdivision and correlation in mesoproterozoic strata.