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1.
广西六景泥盆纪吉维阶-弗拉斯阶界线层牙形石生物地层 总被引：2，自引：1，他引：1
广西六景泥盆系剖面是我国泥盆系标准剖面之一 ,通过对其吉维阶 -弗拉斯阶界线上下地层进行详细的牙形石生物地层研究 ,自上而下识别出 12个牙形石带 :Palmatolepis jamieae带、Palmatolepis hassi带、Palmatolepispunctata带、Palmatolepistransitans带、上 Mesotaxisfalsiovalis带、下 Mesotaxisfalsiovalis带、Klapperina dispar-ilis带、上 Schmidtognathus hermanni- Polygnathus cristatus带、下 Schmidtognathus hermanni- Polygnathus cristatus带、上 Polygnathus varcus带、中 Polygnathus varcus带、下 Polygnathus varcus带。吉维阶 -弗拉斯阶界线 (即中 -上泥盆统界线 )由 Ancyrodella binodosa→ Ancyrodella rotundiloba early form→ Ancyrodella rotundiloba late form这一演化线系中的 Ancyrodella rotundiloba early form的首次出现确定 ,处于下 Mesotaxis falsiovalis带下部 ,在谷闭组底界之上 1.80 m处。 相似文献
2.
Abstract: The Caiziyan Middle and Upper Devonian boundary section is located approximately 30 km northeast of Guilin. It hosts relatively abundant benthic and common–rare pelagic fossils, including brachiopods, corals, tentaculites, and conodonts, which may serve as a better suitable section for pelagic and neritic stratigraphic correlation. In this section, 10 “standard” conodont zones are recognized across the Givetian–Frasnian boundary, including, in descending order, the Lower hassi Zone, punctata Zone, transitans Zone, the Upper falsiovalis Zone, the Lower falsiovalis Zone, disparilis Zone, the Upper hermanni–cristatus Zone, the Lower hermanni–cristatus Zone, the Upper varcus Zone, and the Middle varcus Zone, all of which are defined by the first occurrence of their defining conodont species. The Middle–Upper Devonian (Givetian–Frasnian) boundary is defined by the first occurrence of Ancyrodella pristina in accordance with the Global Stratotype Section and Point (GSSP), which is assigned at 6.2m above the base of bed 19 in the Caiziyan section. 相似文献
3.
笔者在广西象州中坪马鞍山剖面上泥盆统“融县组”中部,首次发现了地层连续、岩性均一、牙形石带齐全的弗拉斯阶/法门阶界线层。这一界线层完全符合国际泥盆纪地层分会(SDS 1983)作出的关于划分弗拉斯阶/法门阶界线条件的决议。并与被誉为盆地相最佳剖面的西德Schmidt剖面(SDS Newsl.1986,no.1,Doc.C)的牙形石序列基本一致。无论是从岩石的均一性或是牙形石生物的连续性上,马鞍山剖面完全可与西德Schmidt剖面媲美,它是目前国内研究弗拉斯阶/法门阶界线的理想剖面之一。本文除了对这一界线进 相似文献
4.
湘中佘田桥剖面上泥盆统弗拉斯阶地层研究新进展 总被引：3，自引：1，他引：2
湘中佘田桥剖面的佘田桥阶大致与弗拉斯阶范围一致 ,其下为吉维阶泥质灰岩 ,含腕足类 Emanuella tak-wanensis等及竹节石 Viriatellina kienelensis等。佘田桥阶自下而上分别为榴江组、蒸水河组、老江冲组。榴江组主要是紫红色粉砂质泥岩 /粉砂岩互层、底部为黑色薄层硅质岩。蒸水河组下部以灰黑色及暗灰色钙质泥页岩为主 ,含介形虫 Bertillonella erecta、B.cicatricosa?、Franklinella calcarata、Entomozoe(N ehdentomis) tenera及菊石 Meso-beloceras?sp.;上部泥质灰岩、似瘤状灰岩、粉砂质泥岩含牙形石 Palmatolepis cf.semichatovae、大型菊石 Mantico-ceras sp.及介形虫 Entomozoe(N ehdentomis) pseudorichterina。老江冲组以泥页岩为主 ,顶部附近则出现一些泥质灰岩、似瘤状泥灰岩层 ,产丰富的小嘴贝类、无洞贝类及弓石燕类等腕足动物 ,少量海绵 (?)及珊瑚等。佘田桥阶的顶界与弗拉斯阶的顶界一致 ,即以无洞贝类和大量四射珊瑚的绝灭为标志 ,而 Yannanellina腕足动物群的出现开始于锡矿山阶 (或法门阶 )。综合各类化石资料 ,佘田桥剖面的榴江组大致相当于牙形石 falsiovalis带— punctata带 ,蒸水河组相当于 L ower hassi带— L ower rhenana带 ,老江冲组相当于 U pper rhenana带— linguiform 相似文献
5.
晚白垩世中国东南沿岸山系与中南地区的沙漠和盐湖化 总被引：25，自引：3，他引：25
晚白垩世在中国东南沿古太平洋西岸地区形成了一条巨大的沿岸山系，其山峰高度在３５００—４０００ｍ之间，东西宽度近５００ｋｍ，挡住了东来的暖湿气流，使中南地区云梦泽内陆水域的广大平原和丘陵地变成了一个热带—亚热带干旱、炎热的半沙漠和盐湖地区，这一古地理和古气候格局一直持续到早第三纪末才开始改变。 相似文献
6.
针对保山地层区熊洞剖面原属栗柴坝组的灰岩进行了牙形石样品分析,总计建立了5个牙形石带,分别为Pterospathodus pennatus procerus带、Kockelella walliseri带、Ancoradella ploeckensis带、Polygnathoides siluricus带和Polygnathus nothoperbonus带。该剖面第8层原属栗柴坝组,Polygnathus nothoperbonus分子的出现证实其为下泥盆统埃姆斯阶的地层,应归为向阳寺组。剖面总体对应志留系温洛克统底部到下泥盆统埃姆斯阶中部,中间缺失志留系罗德洛统卢德福特阶—下泥盆统埃姆斯阶之间的8～10个标准牙形石带,说明该地区后期可能受构造作用影响,志留系和泥盆系界线为断层接触。该剖面牙形石序列的建立一定程度上完善了滇西保山地层区志留系生物地层的研究程度,为下一步该区生物地层格架的建立奠定了基础。 相似文献
7.
N. V. Sennikov T. A. Shcherbanenko I. V. Varaksina N. G. Izokh E. S. Sobolev A. Yu. Yazikov 《Stratigraphy and Geological Correlation》2018,26(3):267-282
The age of the Paleozoic sedimentary successions of the Yuryung-Tumus Peninsula in the Khatanga Gulf is determined as Middle Devonian, late Eifelian, and the beginning of the early Givetian on the basis of the study of brachiopods, ammonoids, nautiloids, bactritoids, gastropods, and conodonts, and in the terminology of the standard conodont succession, these deposits are not older than the late Eifelian Tortodus kockelianus Zone, but include the terminal Eifelian Polygnathus ensensis Zone and the first Givetian Polygnathus hemiansatus Zone and are no younger than the beginning of the early Givetian Polygnathus varcus Zone. The Middle Devonian sedimentary successions of the Yuryung-Tumus Peninsula show the level of the global sedimentary Ka?ak Event. The areas of distribution of the Devonian sedimentary deposits in the Yuryung-Tumus Peninsula in the Khatanga Gulf should be considered as one of the fragments of the regional geological structures of a remote (isolated?) region of the Taymyr Fold System rather than a component of the structures of the northern Siberian Platform. 相似文献
8.
YAO Jianxin JI Zhansheng WANG Liting WANG Yanbin WU Zhenjie LIU Dunyi WU Guichun ZHANG Jianwei LI Suping 《《地质学报》英文版》2011,85(2):408-420
The demarcation of the Lower–Middle Triassic boundary is a disputed problem in global stratigraphic research. Lower–Middle Triassic strata of different types, from platform to basin facies, are well developed in Southwest China. This is favorable for the study of the Olenekian–Anisian boundary and establishing a stratotype for the Qingyan Stage. Based on research at the Ganheqiao section in Wangmo county and the Qingyan section in Guiyang city, Guizhou province, six conodont zones have been recognized, which can be correlated with those in other regions, in ascending order as follows: 1, Neospathodus cristagalli Interval-Zone; 2, Neospathodus pakistanensis Interval-Zone; 3, Neospathodus waageni Interval-Zone; 4, Neospathodus homeri-N. triangularis Assemblage-Zone; 5, Chiosella timorensis Interval-Zone; and 6, Neogongdolella regalis Range-Zone. An evolutionary series of the Early–Middle Triassic conodont genera Neospathodus-Chiosella-Neogongdolella discovered in the Ganheqiao and Qingyan sections has an intermediate type named Neospathodus qingyanensis that appears between Neospathodus homeri and Chiosella timorensis in the upper part of the Neospathodus homeri-N. triangularis Zone, showing an excellent evolutionary relationship of conodonts near the Lower–Middle Triassic boundary. The Lower–Middle Triassic boundary is located at 1.5 m below the top of the Ziyun Formation, where Chiosella timorensis Zone first appears in the Qingyan section, whereas this boundary is located 0.5 m below the top of the Ziyun Formation, where Chiosella timorensis Zone first appears in the Ganheqiao section. There exists one nearly 6-m thick vitric tuff bed at the bottom of the Xinyuan Formation in the Ganheqiao section, which is usually regarded as a lithologic symbol of the Lower–Middle Triassic boundary in South China. Based on the analysis of high-precision and high-sensitivity Secondary Ion Mass Spectrum data, the zircon age of this tuff has a weighted mean 206Pb/238U age of 239.0±2.9Ma (2s), which is a directly measured zircon U-Pb age of the Lower–Middle Triassic boundary. The Ganheqiao section in Wangmo county can therefore provide an excellent section through the Lower–Middle Triassic because it is continuous, the evolution of the conodonts is distinctive and the regionally stable distributed vitric tuff near the Lower–Middle Triassic boundary can be regarded as a regional key isochronal layer. This section can be regarded not only as a standard section for the establishment of the Qingyan Stage in China, but also as a reference section for the GSSP of the Lower–Middle Triassic boundary. 相似文献
9.
四川省盐边县北部稗子田地区的专留系发育良好,牙形刺化石极为丰富,与上覆泥盆系连续沉积,并呈整合接触。该剖面为我国扬子区较为理想的志留纪地层剖面,其代表和反映了扬子区西部一种新的断陷盆地碳酸盐岩沉积类型,丰富了区内志留系的研究内容。笔者详细记述了稗子田专留系至下泥盆统下部剖面的岩性特征和生物化石的垂直分布状部,在此基础上建立和完善区内新的地层系统,提出地层划分的对比依据和建议。新方案除对志留系底的黑 相似文献
10.
河北完县中、晚寒武世牙形石和三叶虫生物地层 总被引：5，自引：1，他引：5
<正> 华北寒武系三叶虫生物地层学的研究历史悠久,目前已趋完善。但凤山期前的牙形石研究是牙形石学研究中的薄弱环节。国外学者对长山阶及以下地层中的牙形石研究甚少,仅Mller(1956)对波罗的海沿岸地区和美国以及Mller et Hintz(1991)对瑞典中南部的寒武系牙形石的研究成果。Miller(1980,1984)在美国西部相当于凤山阶的地层中建立了详细的牙形石带,迄今为止,尚无人在长山阶及之下的地层中建立牙形石带。在国内,安太庠(1982)研究了山东莱芜、河北涞水、辽宁复县和本溪等地的牙形石,并综合 相似文献
11.
Devonian Sea-Level Change Rhythms in South China and Coupling Relationships Among the Earth-spheres 总被引：5，自引：0，他引：5
Gong Yiming Faculty of Earth Science China University of Geosciences Wuhan Hubei Wu Yi Guangxi Institute of Geology Nanning GuangxiDu Yuansheng Feng Qinglai Liu BenpeiChina University of Geosciences Wuhan Hubei 《《地质学报》英文版》1997,71(4):370-385
Twenty orthosequences and their corresponding sea-level change (SLC) cycles have been recognized in the Devonian overlying the Caledonian unconformity, of which 9, 5.5 and 5.5 occurred in the Lower, Middle and Upper Devonian respectively. They can be grouped into 4 orthosequence sets, in which the maximum flooding surfaces lie in the sulcutus Zone (D12), perbonus Zone (D13), Middle and Upper varcus Zone (D22) and gigas Zone (D21) respectively. Four instant palaeogeographical reconstructions of South China have been made in the Emsian and Givetian. Devonian sea-level change rhythms of South China can be divided into 3 categories: the autorhythmic, the worldwide and regional allorhythmic, and the coupling-rhythmic. They developed respectively in the Famennian, Pragian, Eifelian, Lochkovian, Emsian, Givetian, Frasnian and the F / F (between the Frasnian and Famennian) event. The cause of the worldwide allorhythmic SLC of the Pragian and Eifelian under comparatively dry, warm and tranquil conditions may be 相似文献
12.
众所周知,泥盆纪末期曾发生了一次全球性海平面下降事件（D-C事件）,导致绝大多数晚泥盆世生物灭绝,只有少数生物躲过D-C事件残存下来,直到早石炭世最早期才开始复苏,而后辐射演化。全球的资料表明,这些残存下来的生物的演化谱系几乎均被D-C事件打断,牙形类管刺属（Siphonodella）和原颚齿刺属（Protognathodus）的演化谱系被打断。问题的关键在于被D-C事件打断的演化谱系的节点究竟在什么位置,事实表明,管刺属演化谱系中被打断的节点恰好是Si. praesulcta M. 3—Si. praesulcata M. 4演化支系,原颚齿刺属演化谱系中被打断的节点正是Pr. collinsoni—Pr. kockeli演化支系。Si. praesulcata M. 4和Pr. kockeli的所谓首次出现只是地层学含义的最低产出点,而不是生物演化含义的最早出现。这表明,无论是Si. praesulcata M. 4还是Pr. kockeli的首次出现都不适合用来定义泥盆—石炭系界线。通过详细研究牙形类管刺属的分类、谱系和分带,重点研究Siphonodella praesulcata M. 3—Si. praesulcata M. 4的演化谱系,并根据管刺属演化谱系识别出10个牙形类带,即下praesulcata带、中praesulcata带、上praesulcata带、sulcata带、下duplicata带、上duplicata带、下sandbergi带、上sandbergi带、crenulata带和isosticha带,各带基本均以带名种的首次出现底界。Sandberg等1978年提出的以管刺属演化谱系为基础的分带方案是可信、可行的。国际泥盆—石炭系界线工作组1979年提出的泥盆—石炭系界线定义是正确的。因此,目前根本没有必要再修改原来的界线定义,建议仍然以Siphonodella sulcata在Si. praesulcata M. 4—Si. sulcata演化支系中的首次出现来定义泥盆—石炭系界线。目前的主要任务是寻找能展示这种演化谱系的优秀剖面,并将其作为界线层型候选剖面推荐给国际泥盆—石炭系界线工作组。 相似文献
13.
湖北宜昌黄花场中/下奥陶统界线附近几丁虫组合及其地层学意义 总被引：4，自引：1，他引：4
对宜昌黄花场大湾组下段牙形石 Oepikodus evae带至 Baltoniodus triangularis带系统采集与分析几丁虫样品 ,共发现几丁虫 6属 12种 ,其中包括 1个相似种、1个未定种 ,它们是 Conochitina raymondii,C.ordinaria,C.primitiva,C.langei,C.brevis,C.poumoti,C.decipiens,Belonechitina cf.micracantha,L agenochitina esthoni-ca,L.sp.,Eremochitina baculata和 Cyathochitina dispar等。根据上述几丁虫的地质和地理分布特征 ,自下而上可划分为 Conochitina langei带和 Eremochitina baculata带 ,讨论并指出了他们与相关笔石、牙形石生物带的关系 相似文献
14.
对中国海相石炭—二叠系界线典型剖面陕西镇安西口剖面进行了生物地层、层序地层、磁性地层、事件地层多学科综合研究。在石炭—二叠系界线附近建立了4个牙形石生物带,自下而上依次为Streptogna-thoduselegantulus带,S·elongatus带,S·gracilis带和S·isolatus带。将研究区石炭—二叠系界线置于S·isolatus带的底界,较以带Pseudofusulinakrotowisphaeroidea-Dunbarinella(PD)带的底界为标志确定的石炭—二叠系界线层位低3·3m。在西口剖面上石炭统逍遥阶至下二叠统隆林阶,以初始海泛面作为层序界面,识别出12个四级层序(大体相当于副层序组),构成5个Ⅱ型三级层序。这5个三级层序及其对应的海平面变化与贵州独山、罗甸纳水、紫云扁平剖面同期地层中三级层序及海平面变化旋回之间显示出较好的对应关系。除下杨家河阶外,其余各阶的底界,包括逍遥阶、上杨家河阶、范家河阶、垭口阶及隆林阶的底界,基本上都位于沉积相转换点或其附近,即层序地层及海平面变化旋回的关键界面或其附近。表明这5个三级层序的关键界面与年代地层界线的关系相当密切。碳酸盐岩磁化率大小与碳酸盐岩微相存在一定的对应关系,显示相对海平面变化是控制碳酸盐岩磁化率大小的重要因素。另外,在重要地层界线附近常出现磁化率异常高值,说明碳酸盐岩磁化率可能作为地层划分对比的重要依据。西口地区晚石炭世逍遥期至早二叠世隆林期地层中可识别出两次明显的类辐射事件。第一次类辐射事件发生在Occidentoschwagerinaalpina-O·postgallowayi(OS)组合带底部,即下杨家河阶的底部。第二次辐射事件发生在Mccloudiaregularis-Par-aschwagerinafragosa-Robustoschwagerinaxiaodushanica(MPR)组合带底部,即范家河阶的底部。具有三级和三级以上隔壁的四射珊瑚动物群突然大量繁盛,代表四射珊瑚演化进程中一次重大变革。在陕西镇安石炭—二叠系界线附近,这个生物事件首现层位相当于类Pseudofusulinaurdalensi(PU)带下部,高于该带底界不到12m,以Xikouphyllum-Shaannanophyllum-Szechuanophyllum-Wentzellophyllum组合带为代表。在这个层位牙形石也发生了重要变化。各类地质事件记录出现的层位关系密切。在垭口阶底界各类地质事件记录吻合最好,隆林阶底界次之,然后是范家河阶底界。与上述3条界线相比,在镇安西口剖面上,以牙形石Streptognathodusisolatus的首现位置确定的石炭—二叠系界线事件地层特征不明显,既不是一个生物辐射演化面,碳酸盐岩磁化率变化也不太明显,在实际工作中不易使用。 相似文献
15.
四川盐边地区志留纪牙形石生物地层及年代地层 总被引：2，自引：0，他引：2
首次提供了四川盐边地区从下志留统至下泥盆统连续的志留系年代地层系统的实际证据和原始材料,由上而下建立8个牙形石带,2个牙形石组合带和1个笔石带,以此为依据建立了攀枝花阶、永兴阶、箐河阶、叉河阶、透底河阶和支六阶,分别归入下泥盆统、顶志留统、上志留统、中志留统和下志留统,为我国志留系安康阶以上地层的建阶研究工作提供了实际的基础资料。四川盐边地区志留系龙马溪组为笔石相地层,其上全为碳酸盐岩相,其中牙形石发育良好,形成连续完整的牙形石带序列,这对我国和更大的范围壳相志留系年代地层系统对比提供了非常有价值的资料。 相似文献
16.
Devonian sediments of the Malaguide Complex potentially could include the Frasnian–Famennian boundary, one of the five greatest Phanerozoic biotic crises. Conodont biofacies and microfacies of carbonate clasts from a pebbly mudstone underlying Tournaisian radiolarites allows identification, for the first time in the Malaguide Complex, of Devonian shallow marine environments laterally grading to deeper realms. The clasts yielded Frasnian conodont associations of the falsiovalis to rhenana biozones, with six biofacies that reveal different environmental conditions in their source areas. Source sediments were dismantled and redeposited within the pebbly mudstone, whose origin is tentatively related to one of the events that are associated worldwide with the Frasnian–Famennian crisis. The latter is recorded, in two equivalent Malaguide pelagic successions, by stratigraphic discontinuities, and it was, probably, tectonically and/or eustatically controlled, as in other Alpine‐Mediterranean Paleotethyan margins. 相似文献
17.
新疆北部下中泥盆统层序及其界线讨论 总被引：1，自引：0，他引：1
新疆北部是中国北方下中泥盆统出露最全地区之一,1977年曾作为中国北方槽区典型剖面.笔者根据最新资料研究,重新选定了下中泥盆统标准层序(自下而上):下泥盆统:乌吐布拉克组、曼格尔组.芒克鲁组;中泥盆统:乌鲁苏巴斯套组、纸房组.并根据岩性变化及床板珊瑚化石资料,对乌吐布拉克组进行了重新审定,将原沙尔布尔提山剖面乌吐布拉克组下2层归入上志留统.重点讨论了下泥盆统的底界及下与中泥盆统间的界线. 相似文献
18.
Brooks B. Ellwood Jenaro L. García-Alcalde Ahmed El Hassani Jindrich Hladil Francisco M. Soto Montserrat Truyls-Massoni Karsten Weddige Leona Koptikova 《Tectonophysics》2006,418(1-2):31
One major difficulty in geology is high-resolution correlation among widely separated sections, especially in the Paleozoic where magnetostratigraphy polarity is not well established because rocks are often remagnetized, where critical biostratigraphic zonation may be poor or lacking, or where structural complexities make correlations very difficult. To address this problem, we have been using magnetostratigraphy susceptibility measurements. Here, we report our work from the Middle Devonian in Europe and North Africa. The Middle Devonian (Emsian–Eifelian) global boundary stratotype section and point (GSSP), located in the Eifel Hills, western Germany, was ratified by the International Subcommission on Stratigraphy in 1985, after careful evaluation of the biostratigraphy for this and many other sections. The boundary interval has been characterized using biostratigraphy, and the beginning of the Eifelian stage has been specifically defined by the first occurrence of the conodont Polygnathus costatus partitus. We have collected the Eifel Hills section for magnetic susceptibility (MS) measurement and here we establish it as the magnetostratotype for the Emsian–Eifelian stage boundary, by formally defining the magnetostratigraphy susceptibility for the section. We then collected, measured and compared the magnetostratotype to four other sections for which conodont biostratigraphy has been studied and where P. costatus partitus is present; two Emsian–Eifelian sections in Morocco and two sections in the Czech Republic (including the Emsian–Eifelian parastratotype). Finally, we have measured the MS for the El Puerto Creek section in the Cantabrian Mountains of Spain and identified the location of the Emsian–Eifelian boundary within the section based on MS comparison to the GSSP in conjunction with excellent biostratigraphic indicators, primarily brachiopods. While the conodont zonation in the El Puerto Creek section is poorly defined, we believe that the correspondence between the MS and biostratigraphy in the section allows the identification of the Emsian–Eifelian boundary. These results indicate that this method can be successfully applied to marine sequences where ambiguities in correlation exist. 相似文献
19.
西藏色龙西山色龙群的时代及二叠系与三叠系的界线 总被引：3，自引：1，他引：2
《地层学杂志》1992,(4)
<正> 色龙群于1964年由希夏邦马峰登山队科学考察队(1982)命名,层型剖面在聂拉木县色龙村西北约1km的小山上,时代为二叠纪。穆恩之等(1973)认为色龙群的时代属早二叠世晚期。章炳高(1974)、吴望始(1975)、张守信、金玉玕(1976),王玉净、穆西南(1984)对色龙群的时代有类似的看法,均未提及它包含有长兴期地层的存在。饶荣标等(1985)将色龙群分为两组,上部为扒嘎组,下部为门多组。在色龙西山剖面,扒嘎组为生物碎屑灰岩,厚4.15m,含Gertholites curvatus,Thamnopora densa,Pseudofavosites irregularis,Trachypora sp.,Sinkiangopora sp.,时代属晚二叠世,与上覆下三叠统土隆组为整合接触。 相似文献
20.
中国奥陶系和下志留统下部年代地层单位的划分 总被引：1，自引：2，他引：1
十多年来全球和我国奥陶系和下志留统下部年代地层研究取得很大进展 ,在前人所积累的大量成果和资料的基础上 ,结合近年来的研究 ,厘定了我国奥陶系和下志留统下部年代地层单位系统 ,建议分别以吉林浑江大阳岔 (或江西武宁或湖北宜昌黄花场 )、湖北宜昌黄花场、浙江常山黄泥塘、新疆柯坪大湾沟和湖北远安苟家垭剖面为界线层型 ,将中国奥陶系自下而上划分为 :新厂阶 (或特马豆克阶 )、道保湾阶、大湾阶、达瑞维尔阶、艾家山阶和钱塘江阶。为了客观反应我国奥陶系的特点 ,同时便于与全球年代地层单位界线对比 ,建议将上述各个阶底界的的界线依次划在 R.taojiangensis( =R.praeparabola) / H .simplex、 O.communis、 B.triangularis/ T.laevis、 U.austrodentatus、 N .gracilis和 N ankinolithus带的底部 ;中下奥陶统和中上奥陶统之间的界线分别定在道保湾阶 /大湾阶和达瑞维尔阶 /艾家山阶之间。建议下志留统最下部两个年代地层单位——龙马溪阶和大中坝阶——以湖北宜昌王家湾剖面为界线层型 ,分别以 A.ascensus和 D .triangulatus的首现为划分标志。对每一个阶的命名、含义、界线层型剖面的岩性特征、界线划分的生物标志、与全球相关年代地层单位层型和点 ( GSSP)的对比 ,以及与过去曾经建议或使用过? 相似文献