河北唐山—卢龙地区寒武－奥陶系界线地层的牙形刺及其重要属种的演化   总被引：1，自引：0，他引：1  

王志浩  方一亭 《高校地质学报》1996,(4)

本文对唐山和卢龙地区寒武－奥陶系界线地层中的牙形刺再次进行研究，厘定了过去报道的一些重要属种，并对最具地层意义的Ｃｏｒｄｙｌｏｄｕｓ的几个种的演化进行了分析。指出了该属的两个进化系列，第一支进化系列是Ｅｏｃｏｎｏｄｏｎｔｕｓｎｏｔｃｈｐｅａｋｅｎｓｉｓ－Ｃｏｒｄｙｌｏｄｕｓｐｒｉｍｉｔｉｖｕｓ－Ｃ．ｐｒｏａｖｕｓ－Ｃ．ｃａｂｏｔｉ－Ｃ．ｉｎｔｅｒｍｅｄｉｕｓ－Ｃ．ａｎｇｕｌａｔｕｓ；而另一支则是Ｅｏｃｏｎｏｄｏｎｔｕｓｎｏｔｃｈｐｅａｋｅｎｓｉｓ－Ｃ．ｃａｂｏｔｉ－Ｃ．ｐｒｏｌｉｎｄｓｔｒｏｍｉ－Ｃ．ｌｉｎｄｓｔｒｏｍｉ－Ｃ．ｐｒｉｏｎ。本文对寒武－奥陶系界线的几个划分方案也进行了简单的讨论  相似文献   

Structural studies and their bearing on the Early Precambrian history of the Dharwar tectonic province,southern India     

K. Naha  R. Srinivasan  D. Mukhopadhyay 《Journal of Earth System Science》1996,105(4):379-412

In the Dharwar tectonic province, the Peninsular Gneiss was considered to mark an event separating the deposition of the older supracrustal Sargur Group and the younger supracrustal Dharwar Supergroup. Compelling evidence for the evolution of the Peninsular Gneiss, a polyphase migmatite, spanning over almost a billion years from 3500 Ma to 2500 Ma negates a stratigraphic status for this complex, so that the decisive argument for separating the older and younger supracrustal groups loses its basis. Correlatable sequence of superposed folding in all the supracrustal rocks, the Peninsular Gneiss and the banded granulites, indicate that the gneiss ‘basement’ deformed in a ductile manner along with the cover rocks. An angular unconformity between the Sargur Group and the Dharwar Super-group, suggested from some areas in recent years, has been shown to be untenable on the basis of detailed studies, A number of small enclaves distributed throughout the gneissic terrane, with an earlier deformational, metamorphic and migmatitic history, provide the only clue to the oldest component which has now been extensively reworked.  相似文献   

新疆阿尔曼太蛇绿岩时代的Nd—Sr同位素地质研究   总被引：15，自引：7，他引：15  

黄萱  金成伟 《岩石学报》1997,13(1):85-91

本文通过测定采自新疆阿尔曼太兔子泉一带蛇绿岩的堆晶辉长岩、辉绿岩和安山玢岩，获得Ｓｍ－Ｎｄ等时年龄为５６１±４１Ｍａ，εＮｄ（ｔ）＝６．１，Ｒｂ－Ｓｒ等时年龄为３９２±１７Ｍａ，（８７Ｓｒ／８６Ｓｒ）ｉ＝０．７０４１，前者为蛇绿岩的形成时代，后者为蛇绿岩遭受后期变质作用的时间。札河坝－阿尔曼太蛇绿岩的形成环境可能是古亚洲洋向南俯冲引起的弧后盆地  相似文献   

滇东寒武系层序地层学特征     

单卫国 《地质通报》1997,(2)

介绍了对滇东寒武系进行层序地层学研究所采用的方法、层序的基本特征及取得的主要成果。确定有１０个层序，其时限为１～１０Ｍａ，其中下寒统武有６个，中、上寒武统各２个。此外还划分出次层序２７个、组合层序２个。此项研究工作对本区寒武系地层划分与对比、界线的确定具有重要意义：（１）沧浪铺阶生物地层的争论，是由于滇东存在两个Ⅰ型层序边界，乌龙箐段与红井哨段为假整合关系，故生物带发育不完整；（２）双龙潭组与西王庙组应为同时异相沉积体；（３）双龙潭组顶部时限，以ＳＢ２ｉ为标志，应与娄山关组底部边界对比，故可能上延至晚寒武世早期  相似文献   

内蒙古西拉木伦断裂带韧性变形特征     

方曙  王友  樊志勇 《地质通报》1997,(4)

西拉木伦断裂带在早二叠世末发生了韧性右行走滑，形成了包括韧性右行走滑带、韧性压扁带及弱韧性变形带在内的韧性变形带。据动力和运动分析，表明该韧性变形带为一普通剪切带，其中韧性右行走滑带在平面上以简单剪切为主，韧性压扁带在平面上以纯剪切为主。  相似文献   

Ages of Lueliang Group and Its Metamorphism in Mt.Lueliang Region,Shanxi Province：Evidence form Single Grain Zircon U—Pb Dating     

于津海  王德滋等 《中国地球化学学报》1997,16(2):170-177

Presented in this paper are the newly obtained grain zircon U-Pb ages of volcanic rocks of the Lueliang Goup and associated Kuanping granitic migmatitic gneiss in Shanxi Province.The zircon U-Pb ages of bimodal volcanic rocks(basalt and rhyolite)of the Upper Lueliang Group indicate that the rocks erupted at about 2100 Ma.So the Lueliang Group was formed during the Early Proterozoic.In the area studied the second-stage metamorphism experienced by the Lueliang Group is the dominant one which took place at about 1806 Ma.i.e.,during the late Early Proterozoic.  相似文献   

贵州三都早奥陶世同高组下燕高页岩段的生物标志化合物   总被引：8，自引：1，他引：8  

许玩宏  沈平 《沉积学报》1997,15(3):72-77

本文着重报道了贵州三都早奥陶世同高组下燕高页岩段生物标志化合物特征，首次在采自该层位的样品中检出丰富的正烷烃、链状类异戊二烯烷烃、萜类化合物及甾类化合物。测试结果显示:正烷烃图谱呈双驼峰形，碳数分布为ｎＣ_１５～ｎＣ_３５，以ｎＣ_１８为主峰碳，ｎＣ_２９为次主峰碳，Ｃ－_２１/Ｃ＋_２２为０.７７～１.０２，ＯＥＰ为０.９４～１.０４；植烷占优势，Ｐｒ/Ｐｈ为０.４０～０.４６；藿烷碳数为Ｃ_２７～Ｃ_３５，以Ｃ_３０占优势，Ｃ_２７＋Ｃ_２９＜Ｃ＋_３１；仅见碳数分布为Ｃ_２０～Ｃ_２９的长链三环二萜烷，以Ｃ_２８为主峰碳；甾烷丰度顺序为Ｃ_２９甾烷＞Ｃ_２７甾烷＞Ｃ_２８甾烷，同时检出了孕甾烷和４－甲基甾烷。生物标志化合物显示出还原环境特点，且可能主要来自藻类。  相似文献   

Early Estimation of Strong Aftershock Duration Time     

Zhou Cuiying  Wang Hongwei  Wang Mei  and Zhang YuxiaSeismological Bureau of Shandong Province  Jinan  China Center for Analysis  Prediction  SSB  Beijing  China 《中国地震研究》1997,(4)

In order to solve the problem of early estimation of moderately strong aftershock duration time in an earthquake sequence,this study has been conducted.First,the definition of the strong aftershock has been given.It is pointed out that there is a difference in the strong aftershock duration time between the main shock type sequence and the strong earthquake swarm sequence.After dividing the three cases,i.e.,a strong aftershock duration time larger than 1 day,smaller than 1 day,and no strong aftershock occurred in a main shock type sequence by using the pattern recognition method,we gave the rough correlation relation between strong aftershock duration time and first large shock magnitude for two types of sequences.Finally,the judgment index and method of estimating strong aftershock duration times for different sequence types have been given.  相似文献   

强余震持续时间的早期估计   总被引：2，自引：0，他引：2  

周翠英  张宇霞 《中国地震》1997,13(2):164-171

本研究旨在解决地震序列中强余震持续时间的早期估计问题。文中首先给出了强余震的震级定义，指出：主震型与强震群型序列的强作震持续时间存在差异。使用模式识别方法对主震型序列中强余震持续时间大于１天，小于１天及无强余震等３种情况进行划分之后，给出了两类序列的强余震持续时间与序列和第一震震级的粗略相关关系。  相似文献   

中国东部寒武系与奥陶系界线地层的碳氧同位素研究   总被引：12，自引：0，他引：12  

沈渭洲  方一亭 《沉积学报》1997,15(4):38-42

对我国东部不同地层区一些代表性的寒武系-奥陶系界线层位开展了碳?氧同位素研究?结果表明,由于沉积环境差异和成岩蚀变影响,界线层位的δ18O值变化较大,规律性不明显,δ13C值变化虽小,但在界线处均发生不同程度漂移?漂移的层位与寒武纪-奥陶纪主要生物群面貌变化的界线相一致?综合各方面资料分析,笔者认为,碳同位素组成的漂移很可能由晚寒武世到早奥陶世时期内海平面的升降所引起.  相似文献