| 扬子地台早寒武世古盘虫类的地层分布及其古地理控制? |
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| 引用本文： | 杨爱华,朱茂炎,张俊明.扬子地台早寒武世古盘虫类的地层分布及其古地理控制?[J].古地理学报,2005,7(2):219-232. |
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| 作者姓名： | 杨爱华 朱茂炎 张俊明 |
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| 作者单位： | 中国科学院南京地质古生物研究所 江苏南京 210008 |
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| 基金项目： | 国家自然科学基金;国家重点基础研究发展计划(973计划) |
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| 摘 要： | 早寒武世早期的黑色页岩系在扬子地台非常发育，但由于具有时代标志的化石稀少，这套黑色页岩系的层序问题一直未能很好解决。古盘虫类化石是早寒武世黑色页岩系中仅有的具有地层意义的化石类别,然而它们的分类混乱、层位不清，限制了其在地层对比中的应用。在古盘虫类分类重新厘定的基础上，通过对Tsunyidiscus 的4个种和Hupeidiscus orientalis地层分布的系统总结，认为T.aclis和T. armatus的层位限于筇竹寺早期，T. niutitangensis和T. tingi的层位主要是筇竹寺晚期，只有T. tingi延伸至沧浪铺早期。而H. orientalis在筇竹寺晚期开始出现，到沧浪铺早期繁盛。因此它们的层位分布特征可以用于地层学对比。通过对华南地区古盘虫类古地理分布和沉积相与环境分析，我们认为古盘虫类的分布受海平面升降、海水浑浊度、水深、含氧性等古海洋环境因素的控制： T. armats和T. aclis分布于近滨-远滨及外陆架上，适应水体平静，水动力能量较低，低沉积速率的相对较深的海域; T. tingi和T. niutitangensis在开阔的外陆架区域大量繁盛，T. niutitangensis生存在具有分层结构海洋的贫氧带和富氧带，海水较深，水体平静； 而H. orientalis在陆架边缘灰岩相中大量出现，适应于海水较深，水动力能量较低，浮游微生物丰富的洁净海水; 此外在粗碎屑岩、高碳质页岩、石煤发育的地层中无古盘虫类分布, 表明古盘虫类不适合海水动荡而混浊，沉积速率高的浅水高能环境和深水滞流缺氧的环境。
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| 关 键 词： | 扬子地台 早寒武世 古盘虫类 地层 古地理 生态环境 |
| 文章编号： | 1671-1505(2005)02-0219-14 |
| 修稿时间： | 2004年1月30日 |
Stratigraphic distribution and palaeogeographic control on the Early Cambrian Eodiscoids in Yangtze Platform |
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| Yang Aihua,Zhu Maoyan,Zhang Junming.Stratigraphic distribution and palaeogeographic control on the Early Cambrian Eodiscoids in Yangtze Platform[J].Journal of Palaeogeography,2005,7(2):219-232. |
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| Authors: | Yang Aihua Zhu Maoyan Zhang Junming |
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| Institution: | Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, Jiangsu |
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| Abstract: | The Lower Cambrian black shales are well developed on the Yangtze Plat form,but subdivision and correlation of these black shales remain unresolved,b ecause of lack of index fossils. Eodiscoids,which are abundant at some horizon s ,are the only body fossils that can be applied to correlating the Lower Cambria n black shales.However,taxonomy of these eodiscoids from South China is very confused among the palaeontologists and their stratigraphic distribution remains unclear,thus limiting their stratigraphic application.Based on the revised tax onomy and reviewed stratigraphic distribution of the Lower Cambrian eodiscoids on the Yangtze Platform,the present study indicates that the five distinct eodiscoid spec ies show high potential for stratigraphic correlations and their distributions a re controlled essentially by palaeoenvironment.The results demonstrates that T. aclis and T.armatus only occurred in the Early Qion gzhusian,T.niutitangensis and T.tingi mainly occurred in the Late Qiongzhusian,b ut only T.tingi extend ed to the Early Canglangpuian.H.orientalis appeared in the Lat e Qiongzhusian, but are abundant in the Early Canglangpuian.Analyses of the palaeoenvironments indicate that sedimentary rate,sea-level change,seawater depth,redox conditi o n of the bottom water are major environmental factors which control distribution of the eodiscoids.T.aclis and T.armatus occurred in the nearshore to offshor e environments.T.niutitangensis and T.ti ngi were flourishing in the outer she lf,while a large number of H.orientalis occurred in the carbon ate facies under the clear seawater with abundant phytoplankton under the shelf-edge and outer shelf conditions.No eodicoids appeared in the black carbonaceous shale under the deep euxinic anoxic condition of backshore and foreshore basins,and eith er lived in shallow water basin with high hydrodynamic energy and sedimentation rate. |
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| Keywords: | Yangtze Platform Early Cambrian Eodiscoids strat igraphy palaeogeography ecoenvironment |
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