云南东部中—新元古代地层界线的厘定与对比

DEFINING AND COMPARISING FOR MID—LATE PROTEROZOIC ERA STRATA IN EAST YUNNAN

云南东部中上元古界的界线长期以来被置于晋宁运动所造成的不整合界面上。通过近年来的研究,晋宁运动的时限为850—900Ma,与国际地层委员会所确认的中上元古界界线的时限为l000Ma不符。在晋宁运动界面之下广义的昆阳群上部,即大营盘组(或柳坝塘组、军哨组)与下伏昆阳群其它组段之间还存在一不整合界面,其时限为1000Ma±。笔者认为该界面应该是云南东部中上元古界的分界,既可在划分标准上与国际、国内相统一,也可解决与邻区对比上长期存在的混乱状态。

The boundary between Middle and Upper Proterbzoic Erathem in East Yunnan was put on the unconformity interface led by the Jinning Movement for a long time. According to study of recent years, the Jinning Movement has been timed as 850-900Ma. That does not conform to 1000 Ma, the age of dividing line between Middle and Upper Proterozoic Erathem affirmed by the International Commission of Stratigraphy. Under the Jinning Movement inter-face, there is anouther unconformity interface aged 1000 Ma between upper parts of the Kunyang Group in broad sense including the Dayingpan Forma- tion(or the Liubatang Formation, the Junshao Formation)and the other formations of the Kunyang Group. So, this is the proper interface for divi-ding the Middle and Upper Proterozoic Erathem. To affirm it as the inter-face of Middle and Upper Proterozoic Erathem would be convenient not only for unifying the dividing criterion to that of China at home or in the world abroad but also for solving the confused problems in comparision with the neighbouring districts.