地质通报2005，Vol.24Issue(5)：393-400,8.
长江三峡地区埃迪卡拉(震旦)系锆石U-Pb新年龄对庙河生物群和马雷诺冰期时限的限定
New U-Pb zircon ages from the Ediacaran(Sinian) System in the Yangtze Gorges:constraint on the age of Miaohe biota and Marinoan glaciation
摘要
Abstract
New U-Pb ages by sensitive high-resolution ion microprobe (SHRIMP Ⅱ) on zircons were obtained from two tuff samples: one from the boundary of the Dengying and Doushantuo formations, the other from the basal Doushantuo Formarion in the Jiuqunao section, which situated at the western limb of the Huangling anticline in the Yangtze Gorges in Zigui, Hubei Province, South China. Analyzed zircons from the boundary of the Dengying and Doushantuo formations form two dusters. The younger cluster includes 16 spots and after removing one spot deviated from the population mean gives a weighted mean 206Pb/238U age of 549.9±6.1 Ma (MSWD=1.48), which represents the age of the volcanic tuff in this horizon and forms an age constraint on minimum age of Miaohe biota. The other from the basal Doushantuo Formation includes two clusters: one includes three spots, with an inherited age of 784±15 Ma (MSWD=0.05); the other consists of 15 spots and gives a weighted mean 206Pb/238U age of 628.3±5.8 Ma (MSWD=0.86). It is the first SHRIMP U-Pb zircon age obtained nearly the base of the Sinian (Ediacaran) Doushantuo Formation and represents a maximum age of the Doushantuo Formation.The sampling site lies just above the Doushantuo cap carbonate, so the data basically forms an age constraint on the lower boundary of the Sinian (Ediacaran) System. In addition, this age is very close to 630 Ma for the base of the Ediacaran System in the International Stratigraphic Chart published by the International Committee on Stratigraphy in 2004, indicating that the boundary age of the revised Sinian and Nanhuan systems in China should be ～630 Ma.关键词
锆石U-Pb年龄/埃迪卡拉系/长江三峡地区/庙河生物群/马雷诺冰期Key words
U-Pb zircon age/Ediacaran System/Yangtze Gorges/Miaohe biota/Marinoan glaciation分类
天文与地球科学引用本文复制引用
尹崇玉,唐烽,柳永清,高林志,杨之青,王自强,刘鹏举,邢裕盛,宋彪..长江三峡地区埃迪卡拉(震旦)系锆石U-Pb新年龄对庙河生物群和马雷诺冰期时限的限定[J].地质通报,2005,24(5):393-400,8.基金项目
This study is supported by Project 200213000042 of China Geological Survey （）
National Natural Science Formation of Chinagrant 40272015 and Project 20000077700 of the State Plan for Development of Basic Research in Key Areas. （）
