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前寒武纪-寒武纪之交是地球演化历史上最重大的变革时期之一.前寒武纪-寒武纪界线年龄的准确确定对理解超大陆裂解、早期生命辐射、全球生物地球化学循环以及环境变化等一系列全球性的重大科学问题至关重要.云南梅树村剖面曾经是前寒武纪-寒武纪界线全球标准层型剖面和点位的三个候选剖面之一.对梅树村剖面的凝灰岩层(即第5层)进行了高精度SIMS锆石U-Pb定年,对本文13个谐和SIMS数据和Sawaki等人(2008)所测的4个nano-SIMS数据进行加权平均可以得到206Pb/238U年龄为(535.2±1.7)Ma(MSWD=0.53),这很可能是目前对梅树村第5层凝灰岩年龄的最佳估计值.这个新的年龄结果说明梅树村剖面的前寒武纪-寒武纪界线应该更接近小歪头山段底部的A点而不是中谊村段上部的B点,并为华南前寒武纪-寒武纪地层对比提供了一个可靠的年龄控制点.
The Precambrian-Cambrian transition is one of the most significant changes in the history of the Earth’s evolution An accurate definition of the Precambrian-Cambrian boundary To understand the implications of the supercontinental pyrolysis, early life radiation, global biogeochemical cycles, and Environmental changes and a series of major global scientific issues is crucial.Meshun village in Yunnan Province was once the Precambrian - Cambrian boundary line of the world standard layer profile and the point of the three candidate profiles of plum We performed a high accuracy SIMS zircon U-Pb dating on the tuff layer (ie, the fifth layer) of the village profile. The 13 harmonic SIMS data in this paper and the four nano-SIMS data measured by Sawaki et al. (2008) The 206Pb / 238U age of (535.2 ± 1.7) Ma (MSWD = 0.53) can be obtained, which is likely to be the best estimate for the tuff age at layer 5 in Meishu village. The new age result shows that The Precambrian-Cambrian boundary should be closer to point A at the bottom of Xiaowusuituan rather than point B at the upper part of Zhongyicun and provide a reliable basis for the Precambrian-Cambrian stratigraphic correlation in southern China Age control point.