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建立中国晚前寒武纪地层标准剖面一直是华北中、新元古代地层研究的主要目标,获得高质量同位素年龄数据是实现这一目标的关键之一.然而,多年来关键层位仍缺乏高质量同位素年龄的约束.对原“青白口系”下马岭组的层凝灰岩进行研究,并在河北省宣化地区下马岭组发现10层凝灰岩层(斑脱岩),获得大量岩浆型锆石,利用SHRIMPⅡ技术,进行了高精度定年,测得凝灰岩层锆石207Pb/206Pb加权平均年龄为(1366±9)Ma.结合区域资料和北京西山下马岭组的锆石年龄讨论了锆石年龄的地质意义.这一新的同位素年龄数据为华北“青白口系”下马岭组在地层柱中的定位增添新的依据,它不仅再次准确地确定了地层的形成时代,而且对整个华北地台中、新元古代地层的地质演化史的认识和下马岭组宏观藻类演化在中元古代年代地层柱准确定位都有着重要的地质意义.
The establishment of the standard profile of the Precambrian stratigraphic in China has been the main objective of the research on the Mesozoic and Neoproterozoic strata in North China, and obtaining high-quality isotope age data is one of the keys to achieve this goal. However, Mass isotopic age.Studied on the tuff of the original “Qingbaikoukei” Xiamaling formation, 10 layers of tuff (bentonite) were found in the Xiamaling Formation of Xuanhua area, Hebei Province, and a large number of magmatic zircons , And the dating of 207Pb / 206Pb zircons in the tuff layer was determined to be (1366 ± 9) Ma using SHRIMPⅡtechnique.According to the data of the combining area and the zircon age of the Xiamaling Formation in Xishan, Beijing, the zircon age Geological significance of the new isotope age data for the North China “Qingbaikou system ” Xiamaling group positioning in the column to add a new basis, it not only once again accurately determine the formation of the formation of the era, but also for the entire North China The understanding of the geological evolution history of Taichung and Neoproterozoic strata and the macroscopic algae evolution in Xiamaling Formation all have important geological significance in the accurate positioning of the strata column in the Mesoproterozoic.