对云南晋宁梅树村震旦系-寒武系界线层型(候选)剖面的一些新认识

本文介绍了全球范围内当前已知的前寒武系-寒武系界线层型候选剖面中最优秀的云南晋宁梅树村剖面的最新研究材料。认为该剖面小歪头山段与下伏白岩哨段岩性甚为接近,两者应予合并。梅树村阶进一步划分出来的各亚组合带不能成立。许多材料都说明白岩哨段顶部和大海段顶部均有短期沉积间断。梅树村剖面前寒武系-寒武系界线点选择在“B”点,也即Anabarites trisulcatus组合带与Paragloborilus subglobosus组合带分界点上最合适。

A NEW UNDERSTANDING ON MEISHUCUN SINIAN-CAMBRIAX BOUNDARY SECTION IN JINNING, YUNNAN

The Meishucun Sinian-Cambrian boundary section in Jinning County, Yunnan Province is the best sec-tion of known Precambrian-Cambrian boundary stratotype sections (recommended) on a global scale atpresent. The authors agree with the eurr?nt stratigraphic subdivision of most of the members, except the Xiaow-aitoushan member. The strata which contain pre-trilobite metazoan (earliest skeletal faunas) are pertinent tohave subdivided into three assemblage zone?, i. e. Anabarites trisulcatus, Paragloborilus subglobosus and Sinos?-chites triangularis. The newly found facts are as follows. (1) The lithology of the Xiaowaitoushan and the Baiyanshao members is identical, so the classificationof Xiaowaitoushan should be discarded. (2) The thickness of Bed 6 and 7 is inconsistent with the facts. It should be 3.5m and 2.1m, respec-tively. (3) All the sub-assemblages of the Meishu?un Stage can not be proved. (4) Short-term depositional breaks at the top of Baiyanshao and Dahui members have been found. (5) Precambrian-Cambrian boundary on the Meishu?un section should be pinpoint at "B" between theA. trisulcat?s Assemblage Zone and the P. subglobosus Assemblage Zone.