论吉林浑江大阳岔寒武、奥陶系的分界 |
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引用本文: | 钱义元. 论吉林浑江大阳岔寒武、奥陶系的分界[J]. 地层学杂志, 1987, 0(4) |
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作者姓名: | 钱义元 |
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摘 要: | <正> 我国寒武-奥陶系界线的研究在20年代就已涉及(孙云铸,1923),周志毅、张进林(1978)认为我国北方寒武-奥陶系的界线应该划在上寒武统的Mictosaukia orientalis组合与下奥陶统的Onychopyge-Leiostegium组合之间;并且认为这条界线大致可与澳大利亚昆士兰上寒武统Payntonian顶部的Mictosaukia perplexa带与下奥陶统Datsonian底部Cordylodus proavus带之间的界线进行对比。周志毅、王志浩等(1984)根据三叶虫、
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On the Cambrian-Ordovician boundary at Dayangcha of Hunjiang, Jilin |
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Abstract: | e Cambrian-Ordovician boundary sections in North and Northeast China were studied in detail by several Chinese palaeontologists and geologists (Zhou et al., 1978, 1984; Kuo et al., 1982; Duan et al., 1986). In the previous papers, the boundary was traditionally drawn at the top of the Mictosaukia Zone. After studying the Dayangcha candidate Cambrian-Ordovician boundary stratotype section, the writer thinks it belter to put the Cambrian-Ordovician boundary between the Richardsonella-Platypeltoides and Leloste-giatn (Manitouella) Assemblage Zones than to put at the top of the Mictosaukia Zone. Because 6 genera of trilobites abruptly disappeared at the top of the Richardsonella-Platyfeltoides Assemblage Zone, and two genera of trilobites suddenly appeared at the beginning of the Leiostegium (Manitouella) Assemblage Zone. According to the Calgary Meeting, July 1986, the Cambrian-Ordovician boundary will be defined above the conodont zone at or just below the earliest appearance of nematophorous graptolites. The proposed Cambrian-Ordovician boundary based on conodont Cordylodus lindstromi is 6.5m higher than that based on trilobites. The Dayangcha Cambrian-Ordovician boundary section yields abundant conodonts, graptolites and trilobites. |
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