摘要
我国青白口系一直归属新元古界。近年来,青白口系下马岭组斑脱岩U-Pb同位素SHRIMP法测年为1368±12 Ma,1370±11 Ma,1366±9 Ma等,时代为中元古代。长龙山组至景儿峪组含宏观藻类化石Chuaria-Tawuia-Long-fengshania组合,与北美劳伦古陆西缘加拿大西部麦肯齐山地区新元古界小达尔群所含Chuaria-Tawuia-Longfengsha-nia宏观藻类化石组合完全可以对比,而骆驼岭组(=长龙山组)206Pb-238U测年为930±10 Ma,长龙山组至景儿峪组的时代应为新元古代。长龙山组与下伏下马岭组在燕山地区有明显的沉积间断,则青白口系应解体为下部属中元古界,上部归新元古界。因此,青白口系的含义显然应该重新修订,"青白口系"一名应废弃不用。下马岭组与下伏铁岭组也为明显的沉积间断,通过地层区域对比,金县群与下马岭组地层层位相当,金县群的时代相应也为中元古代,并且地层连续,出露较全,金县群提升为系一级的地层单元就更为恰当(同位素年代推测为1400 Ma～1000 Ma或1400Ma～1200 Ma)。青白口系含义的重新厘定与区域对比和金州系的建立,理顺了我国中-新元古代的地层序列和年代地层格架,为建立系一级的年代地层单元提供了地层基础,具有重要的地层学和地质年代学意义。
In 1934 year, Qingbaikou System is established in Jixian County, Hebei Province,Northem 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 ± 12 Ma. Another zircon U-Pb age gained from the same formation in Zhaojiashan,Hebei Province,yielding similar age（weighted mean 206pb/238U）1366 ± 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.
出处
《地质调查与研究》
2013年第1期1-9,共9页
Geological Survey and Research
基金
全国地层委员会项目:中国主要断代地层建阶研究(200113900076)
国家地调项目:晋冀成矿区地质矿产调查(基[2011]矿评01-08-09)
关键词
青白口系
区域对比
金州系
Stratigraphycal correlation
Qingbaikou System
Jinzhou System establish
