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一般认为滇中震旦系是以晋宁运动造成的不整合面为底界。但是,关于震旦系的下限年龄有两种不同的意见,即900或800百万年。作者在滇中罗茨地区作地质研究时,在澄江组的下部发现一套火山岩系。该区澄江组可以分为两部分:下部是大陆喷发的玄武岩,可与川西地区的苏雄组对比;上部是河流相红色碎屑沉积,可与滇中地区的澄江组对比。它是苏雄组和澄江组之间过渡类型,是同期异相的沉积。中国科学院地质研究所测定火山岩的铷—锶等时线年龄为885百万年、这是云南澄江组唯一的直接年龄。侵入在火山岩中的微岗岩经冶金工业部地质研究所测定其铷—锶等时线年龄为705百万年。另外,川西苏雄组中部英安岩的年龄为822百万年,滇中昆阳群柳坝塘组炭质板岩的年龄为1002百万年。综合考虑这些年龄值,晋宁运动终结的时间大致应在9亿年左右。因此,将震旦系的下界年龄划在9亿年左右是恰当的。
It is generally believed that the Sinian in Central Yunnan is based on the unconformity resulting from the Jinning movement. However, there are two different opinions about the minimum age of the Sinian, 900 or 800 million years. When the author conducted a geological study in the Roots area of central Yunnan, he discovered a volcanic series in the lower part of the Chengjiang Formation. The Chengjiang Formation in this area can be divided into two parts: the lower part is the basalt erupted in the mainland and can be compared with the Suxiong Formation in the western Sichuan area; the upper part is the red clastic sediments of the river facies, which can be compared with the Chengjiang Formation in the central Yunnan. It is a transitional type between Suxiong Formation and Chengjiang Formation and is a deposition of heterogeneous phase over the same period. The Institute of Geology, Chinese Academy of Sciences measured the volcanic rock’s rubidium-strontium isochron age of 885 million years, which is the only direct age of Yunnan Chengjiang Formation. Intrusion of volcanic rocks in the granite by the Ministry of Metallurgical Industry Institute of Geology determination of its rubidium - strontium isochron age of 705 million years. In addition, the age of the dacite of the central Suxian Formation in western Sichuan is 822 million years, and the age of the carbonaceous slate of the Kunyu Qunliutang Formation in Central Yunnan is 1002 million years. Taking these age values into consideration, the time for the end of Jinning Campaign should be roughly 900 million years. Therefore, it is appropriate to set the lower bound of the Sinian to about 900 million years.