摘要
界线点的确定及其延仲对比,是解决前寒武系—寒武系界线、划分及洲际对比必不可少的前提。南亚地区发育众多优良的界线剖面,不仅具备选择界线层型的条件,也具备解决界线剖面长距离对比问题的基础。本文通过对华南、小喜马拉雅山、厄尔布尔兹山三地区典型剖面最新区域资料的详细分析研究,确定了界线点的位置,提出对比方案,较好地解决了界线剖面的大范围对比问题。
In the study of the worldwide Precambrian-Cambrian boundary problem,South Asia occupies an important position because it not only provides typical sections such as the Meishutun section but also the Meishucunian strata and fauna have been broadly discovered in it.Through many years of study,abundant information has been collected.Now conditions are available for solving the problem of correlation between those sections.Point"A"follows the resolution of the Precambrian—Cambrian Boundary Woring Group in the Cambridge Conference in Jan.1978 about"The Precambrian—Cambrian boundary stratotype point should be placed as close as is praticable at the base of the oldest stratigraphic unit to yield small shelly fossil assemblages".The modified point satifying the resolution of the Bristol Conference of the Working Group in May 1983 on the principle of"The Precambrian—Cambrian boundary stratotype point should be as close as practicable to the base of the earliest sequence with diverse shelly fossil assemblages with a good potential for correlation"is used as point"B".The point where the oldest trilobites began to appear is used as point"C".On the Upper Yangtze platform of China,the point"A"is located at the bottom of assemblage zoneⅠ,the point"B"at the level between assemblage zonesⅠand Ⅱ,and the point"C"at the top of assemblage zone Ⅲ.In the Higher and Lesser Himalayas in the northwest part of India,the point"A"should be placed at the bottom of the phosphorite-bearing member,the point"C"at the top of the Arenaceous Member,and the point"B"in the inner Arenaceous Member.In the Alborz Mts.of northern Iran,the point"A"should be placed at the bottom of the middle dolomite Member,the point"B"at the bottom of the Upper Shale Member.From the above,the correlation of those typical sections is no trouble.
作者
蒋志文
M.D.Brasier
B.Hamdi
Jiang Zhiwen;M.D.Brasier;B.Hamdi(Yunnan Institute of Geological Sciences,Kunming,Yunnan Province,P.R.C;Department of Geology,University of Hull,Huil Hu6 7RX,England;Geological Survey of Iran,P.O.Box 1964,Teheran,Iran)
出处
《地质学报》
1988年第3期191-199,共9页
Acta Geologica Sinica
