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湖北西部宜昌王家湾北剖面观音桥层底界之下0.39m处被定义为上奥陶统最后一个阶—赫南特阶的全球界线层型剖面和点位(GSSP),但此颗“金钉子”却缺乏可信的同位素年代学数据.对王家湾北剖面观音桥层顶部斑脱岩的锆石进行了高精度离子探针(SHRIMPⅡ)定年研究.结果表明,观音桥层顶部斑脱岩形成年龄为(443.2±1.6)Ma,也就是说,赫南特阶顶部即奥陶系/志留系界线处的同位素年龄应接近但略小于(443.2±1.6)Ma,此年龄与国际地层委员会公布的奥陶系/志留系界线年龄(443.7±1.5)Ma在误差范围内一致.因此,这一研究为赫南特阶和奥陶系/志留系界线的全球对比提供了可靠的年代学依据.
The 0.39 m below the basement of the Guanyinqiao layer in the northern section of Wangjiawan, Yichang, western Hubei Province is defined as the global boundary layer profile and point (GSSP) of the Upper Ordovician, the last order of the Upper Ordovician. However, Gold nail "is lacking in credible isotopic geochronology data.High-precision ion probe (SHRIMPⅡ) dating of zircon from the top of the Guanyinqiao layer in the Wangjiawan northern section was conducted.The results show that the top spots The age of detachment is (443.2 ± 1.6) Ma, that is to say, the isotopic age at the top of the Hernández-Ordovician / Silurian boundary should be close to but slightly less than (443.2 ± 1.6) Ma, The Ordovician / Silurian boundary line age (443.7 ± 1.5) Ma published by the formation committee is within the error range, so this study provides a reliable basis for the global comparison of the Hernández-Dante and Ordovician / Silurian boundaries Chronological basis.