Recently Ratified and Proposed Cambrian Global Standard Stratotype-section and Points

This paper briefly summarizes an officially ratified Global Standard Stratotype-section and Point (GSSP) and a proposed GSSP for global stages of the Cambrian System. The Luoyixi section near Luoyixi town, Guzhang, northwestern Hunan is ratified as the boundary stratotype for the base of the global Guzhangian Stage, which is the upmost stage of an unnamed series termed provisionally as Cambrian Series 3. The GSSP position lies 121.3 m above the base of the Huaqiao Formation in the section, coinciding with the first appearance of the cosmopolitan agnostoid trilobite Lejopyge leavigata. The Duibian B section at Duibian village, Jiangshan, western Zhejiang, is proposed as the boundary stratotype for the base of the proposed global Jiangshanian Stage that is the second stage of the Furongian Series. The proposed GSSP position lies 108.12 m above the base of the Huayansi Formation in the section, coinciding with the first appearance of the cosmopolitan agnostoid trilobite Agnostotes orientalius. This horizon is also with the first appearance of the cosmopolitan polymerid trilobite Irvingella angustilimbata.     

Conodont Biostratigraphy and Age Determination of the Lower-Middle Triassic Boundary in South Guizhou Province,China

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 ca...     

A Comprehensive Evaluation on the Devonian-Carboniferous Boundary Stratotype Candidate Section in Nanbiancun, Guilin, Guangxi

This paper presents a comprehensive evaluation on the Devonian-Carboniferous Boundary (DCB) sectionin Nanbiancun. Guilin. Guangxi on the basis of Palaeontological, biostratigraphical and sedimentarypetrological studies as well as microfacies analysis. REE and trace element analysis and isotopic dating. The DCB at this section conforms to the definition of this boundary and essentially measure up the criteriaand conditions for selection of the boundary stratotype. Up to 14 fossil groups are contained in the section. Thesection presents a general biostratigraphical framework with multispecies fossils zones, assemblage zones andmultiple groups of fossils and has latent preponderant conditions for magnetostratigraphic andchronostratigraphic studies. The boundary and point occur in a persistent and continuous monofacialcarbonate succession. and the section is located in a tourist city with convenient communication, where variousfacies of DCB sections are developed. allowing the correlation within a small area. So it is an ideal candidateboundary stratotype.     

New Advances in the Study of the Devonian-Carboniferous Boundary Stratotype in Muhua,Changshun,Guizhou——An Introduction to the Daposhang Devonian-Carboniferous Boundary Section

The Daposhang section at Muhua, Changshun. Guizhou. is an excellent and attractive DevonianCarboniferous boundary section. The transitional beds between the Devonian and Carboniferous of the sectionare continuous and well exposed. belonging to the deep-water basin facies Abundant fossil groups have beendiscovered from this section: conodonts. ammonoids. trilobites. ostracods. vertebrate microfossils and so on.So far as known. it has the most continuous and complete conodont zonation for the Devonian-Carboniferousboundary beds in the world. It is especially worth pointing out that both typical Siponodella pracsulcata andthe transitional forms between S. praesulcata and S. sulcata have been found from the upper pracsulcata Zoneof the Daposhang section. Evidently. we can not only prove the actual existence of the evolutionary lineagefrom S. praesulcata to S. sulcata, but also exactly define the level of the Devonian-Carboniferous boundary. Inthis paper. the development of the Devonian-Carboniferous boundary beds at the Daposhang section is dealtwith and the section is compared with the Muhua section and the Nanbiancun section which are the candidatesfor the Devonian-Carboniferous boundary stratotype. In the authous opinion the Daposhang section is obvi-ously better than the Muhua and the Nanbiancun sections. hence it can be recommended as one of the candi-dates for the international Devonian-Carboniferous boundary stratotype.     

Conodonts from the Upper Cambrian Sesong and Hwajeol Formations in the Sabuk Area, South Korea

This paper presents a conodont biostratigraphic study on the Upper Cambrian Sesong and Hwajeol Formations in the Sabuk area, Korea. Two samples near the base of the Sesong Slate at the Pukil section contain lower Upper Cambrian conodonts, comprising Furnishina furnishi, F. kranzae, F. pernical, F. triangulate, Hertzina elongata, Laiwugnathus doidyxus?, Phakelodus elongatus, Muellerodus? obliquus, Westergaardodina matsushitai and W. moessebergensis. This is the first conodont record of the Upper Cambrian formations recovered yet in the northern limb of the Paekunsan syncline. The faunal assemblage is correctable with the lower Upper Cambrian W. matsushitai Zone of North China. Four local biozones are recognized in the Hwajeol Formation, i.e. the Proconodontus, Eoconodontus notchpeakensis, Cambrooistodus minutus and Cordylodus proavus Zones in ascending order. This zonal scheme is essentially equivalent to that of the southern limb of the Paekunsan syncline and they are correlatable with zones in other pa     

Conodont Biostratigraphy and Age Determination of the Lower–Middle Triassic Boundary in South Guizhou Province, China

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.     

Trilobite Biostratigraphy of the lower Paleozoic (Cambrian–Ordovician) Joseon Supergroup, Taebaeksan Basin, Korea

In Korea,trilobites are among the most intensively studied fossil groups in the past century and provide invaluable information about lower Paleozoic stratigraphy,paleogeography,and tectonics of the Korean Peninsula. Trilobites occur in the lower Paleozoic Joseon Supergroup of the Taebaeksan Basin which was part of the Sino-Korean Craton in the Paleozoic. The Joseon Supergroup is divided into the Taebaek,Yeongwol,and Mungyeong groups. The Taebaek and Yeongwol groups are richly fossiliferous,while the Mungyeong Group is poorly fossiliferous. Contrasting trilobite faunal contents of the Taebaek and Yeongwol groups resulted in two separate biostratigraphic schemes for the Cambrian–Ordovician of the Taebaeksan Basin. A total of 22 biozones or fossiliferous horizons were recognized in the Taebaek Group; 19 zones were established in the Yeongwol Group; and four biozones were known from the Mungyeong Group. These trilobite biozones of the Taebaeksan Basin indicate the Joseon Supergroup ranges in age from the Cambrian Series 2 to Middle Ordovician and can be correlated well with the formations of North China,South China,and Australia.     

An Update of Conodonts in the Induan-Olenekian Boundary Strata at West Pingdingshan Section, Chaohu, Anhui Province

The Lower Triassic in Chaohu (巢湖) area, Anhui (安微) Province, China, is well developed and its sequence is typical in South China. After a brief introduction of the Induan-Olenekian boundary of Chaohu, this article presents some new data on conodonts. More than ten times of conodont samplings and investigations have recovered thousands of conodont specimens, which are especially rich in the Induan-Olenekian boundary strata at the West Pingdingshan Section in Chaohu City, Anhui Province. The most distinctive forms are the conodonts of the Neospathodus dieneri group and N. Waageni group. The first occurrence of N. Waageni eowaageni, which is regarded as the indicator of the Induan-Olenekian boundary, is situated at 40.49 m above the base of Yinkeng (殷坑) Formation. Some key conodonts and seven new specimens are introduced.     

The GSSP of the Second （Upper） Stage of the Lower Ordovician Series： Diabasbrottet at Hunneberg, Province of Vaeistergoetland, Southwestern Sweden

Diabasbrottet, selected by the International Subcommisson on Ordovician Stratigraphy and in 2002 ratified by the International Commission on Stratigraphy as the GSSP of the Second (Upper) Stage of the Lower Ordovician, is located on the Hunneberg Mountain in southwestern Sweden. The stratigraphic succession represents an outer shelf environment near the Baltic Shield margin. The shale-dominated, biostratigraphically complete, richly fossiliferous boundary interval is completely exposed in a disused quarry. The GSSP is in the lower TФyen Shale 2.1 m above the top of the Cambrian and is marked by the first appearance of the graptolite Tetragraptus approximatus Nicholson. The boundary interval contains a diverse graptolite fauna and biostratigraphically diagnostic conodonts and trilobites that make it possible to define the boundary in terms of zone schemes based on these groups. In this respect, the Diabasbrottet and nearby sections are unique in the world among described localities having this boundary interval. Based on the appearance of T. approximatus, the base of the Second Stage can be identified in many graptolitiferous successions round the world but this level is currently more difficult to recognize precisely in some carbonate sequences outside Baltoscandia. We propose the Second Stage be called the Floan Stage. It is named for the Village of Flo, which is situated about 5 km southeast of the GSSP.     

Conodonts from the Sesong Slate and Hwajeol Formation (Guzhangian to Furongian) in the Taebaeksan Basin, Korea

Abundant conodont elements have been recovered from the Hwajeol Formation, to allow five zones to be erected: Proconodontus, Eoconodontus notchpeakensis, Cambrooistodus minutus, Cordylodus proavus, and Fryxellodontus inornatus-Monocostodus sevierensis-Semiacontiodus lavadamensis zones, in ascending order. More confident biozones are recognized in the Sesong Slate and lower Hwajeol Formation in the Makgol section, a part of the southern limb of the Baekunsan syncline, Taebaeksan Basin, Korea, especially focusing on the conodont biostratigraphic boundary of two units, and the subdivision potential of the previous "Proconodontus Zone", lowermost biozone of the Hwajeol Formation. Similarly, only a few conodont elements recovered from upper 14.5 m interval, namely the Furongian portion of the Sesong Slate, in the Makgol section did not allow erection of a biozone. Nevertheless, this part of the unit plus the basal 2.5 m interval of the Hwajeol Formation is characterized by the occurrence of Prooneotodus rotundatus(Druce and Jones), Teridontus nakamurai(Nogami), Phakelodus elongatus(An) and Phakelodus tenuis Müller. This interval marks the early Furongian "Prooneotodus rotundatus Zone". The rest of the measured section yielded relatively abundant conodonts, so three conodont biozones are proposed, based on the successive appearance of key species: Proconodontus tenuiserratus, Proconodontus posterocostatus, and Proconodontus muelleri zones, in ascending order, and thus allowing subdivision of the previous "Proconodontus Zone". The four conodont biozones are correlated with the relevant biozones of North and South China, and North America.     

芙蓉统和排碧阶底界全球层型剖面的牙形刺生物地层

寒武系芙蓉统和排碧阶全球层型剖面——湖南花垣排碧剖面底界界线层的牙形刺生物地层,由下至上划分为Westergaardodina tetragonia带、Westergaardodina matsushitai带和Westergaardodina bicuspidate 3个牙形刺带,可与该界线层的三叶虫带进行很好对比;同时讨论了芙蓉统和排碧阶底界划在牙形刺Westergaardodina mat-sushitai带和Westergaardodina bicuspidata带之间的合理性;此外,还将该牙形刺分带与华北和东北地区寒武系牙形刺带进行了对比。     

湘西中、晚寒武世牙形刺研究现状及存在问题

湘西中、上寒武统剖面在寒武系全球层型的竞争中具有明显优势 ,其中三叶虫生物地层研究已取得重大进展 ,但一些重要层段的牙形刺详细研究尚未进行 ,而牙形刺在全球界线层型研究中发挥着愈益重要的作用。文内详细介绍了湘西中、晚寒武世牙形刺的研究现状及存在问题 ,并结合《国际地层指南》(第二版 )对全球层型的要求以及国际地层委员会寒武系分会的最新工作进展 ,提出了今后几年湘西中、晚寒武世牙形刺的研究方向及主要任务是建立该地区中、上寒武统候选层型剖面的标准牙形刺序列 ,为我国摘取寒武系内部的“金钉子”并力争用中国的阶填补《国际地层表》中寒武系的空白提供重要依据     

全球奥陶系底界的“金钉子”问题及我国特马豆克阶(Tremadocian)的划分与对比

对全球寒武系与奥陶系界线层型剖面和点位(GSSP)——西纽芬兰绿岬(Green Point)剖面和我国吉林白山(原浑江)大阳岔小洋桥原全球寒武系与奥陶系界线候选剖面的对比研究表明,绿岬"金钉子"剖面所指定的界线生物标志——波动古大西洋牙形石(Iapetognathus fluctivagus)并不存在于所指定的界线生物层和点位上,而且在分布和分类上是均存在争议的物种,更遗憾的是,所展示的大部分牙形石和笔石标本图片以及碳氧同位素异常数据也并非来自该"金钉子"剖面,因而完全违背了选择金钉子剖面的原则和要求,有必要进行重新的评估。小洋桥寒武系与奥陶系界线剖面交通方便、环境优美,寒武系与奥陶系界线地层系由一套深水且未变质的黑色、黄绿色页岩与灰色薄层瘤状灰岩所构成的韵律沉积组成,并保存了完整的具有广泛代表性牙形石和笔石序列,在详细研究的34 m界线间隔中,自下而上保存了完整的Cambrostodus、Codylodus proavus、C.intermedius、C.lindstromi和C.angulatus等5牙形石生物带,在C.intermedius带上部至C.angulatus带之间,还依次出现3层笔石,归属于重新厘定的Rhabdinopora parabola和Anisograptus matanensis等2个笔石带,此外还有大量三叶虫和介形类化石共生,结合高精度同位素地球化学的研究,笔者等建议,以全球广泛分布的牙形石C.intermedius的首现,取代Iapetognathus fluctivagus,作为寒武系与奥陶系界线划分对比的标志,其层位与原来所指定的界线层几乎一致或接近,界线之上所记录的最大碳同位素异常和首次出现的最早的浮游正笔石——R.parabola(含R.praeparabola),可作为该界线划分的辅助标志。     

河北完县中、晚寒武世牙形石和三叶虫生物地层

<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     

滇东下寒武统含磷岩系底部火山喷发事件沉积及其意义

云南曲靖德泽剖面下寒武统梅树村组待补段底和晋宁梅树村剖面小歪头山段底粘土岩层的岩石、矿物和元素地球化学特征表明，这些粘土岩层是由酸性火山灰蚀变而成的变斑脱岩。它们是同期火山喷发事件沉积的标志，也是滇东地区下寒武统梅树村组底界等时对比的标志层。根据这个标志层以及小歪头山段和待补段沉积序列的对比，梅树村剖面小歪头山段仅相当于小江断裂以东地区的待补段下部白云岩层，缺失上部硅质岩层，因而它不能代表滇东地区下寒武统梅树村组下段的沉积序列。     

山东青州尧王山地区寒武系-奥陶系界线及地层划分

鲁西地区的晚寒武世——早奥陶世地层，由于发生了较强烈的白云岩化作用，地层中的沉积构造和生物化石几乎消失殆尽，地层划分对比很困难，甚至寒武系与奥陶系的界线也难以确定。调查发现，青州尧王山地区该时期的地层发育齐全，白云岩化程度较弱，牙形石化石丰富，可与国际层型剖面对比，是鲁西地区完善地层划分和确定寒武系与奥陶系界线的理想地区。     

辽宁太子河流域奥陶系新观察兼论寒武-奥陶系界线

<正> 辽宁太子河流域的奥陶系经王钰等(1954)研究并取得重要进展以后,已成为华北地区奥陶系的典型剖面和对比基础。1979年8—9月间,笔者在本溪、田师付和辽阳五顶山等剖面采集了化石并着重对区内凤山组的生物群序列、寒武系与奥陶系之分界、奥陶纪地层系统及动物群序列等问题作进一步补充研究和探讨。 野外工作期间得到赵祥麟、段吉业、梁仲发等支持和帮助;施从广鉴定介形虫,杨荣庆     

Carbon isotope composition of Upper Cambrian to Lower Ordovician carbonate in Korea,and its bearing on the Cambrian–Ordovician boundary and Lower Ordovician paleoceanography

This study presents an example of locating Cambrian–Ordovician boundary in the lower Paleozoic carbonate succession in Korea using carbon isotope stratigraphy. The Yeongweol Unit of the lower Paleozoic Joseon Supergroup comprises the Upper Cambrian Wagok Formation and the Lower Ordovician Mungok Formation in the Cambrian–Ordovician transition interval. Conventionally, the boundary was placed at the lithostratigraphic boundary between the two formations. This study reveals that the boundary is positioned in the basal part of the Mungok Formation based on the carbon isotope stratigraphy coupled with biostratigraphic information of conodont and trilobite faunas. The δ¹³C curve of the Lower Ordovician Mungok Formation shows a similar trend to that of the coeval stratigraphic interval of Argentine Precordillera (Buggisch et al., 2003), suggesting that the δ¹³C curve of the Mungok Formation reflects the Early Ordovician global carbon cycle.     

Conodonts from the Cambrian–Ordovician boundary interval in the southeast margin of the Sichuan Basin,China

Conodonts from the Cambrian–Ordovician transition at the Liangcun section in Xishui County, Guizhou and at the Huangcao section in Wulong County, Chongqing are examined for the first time. Both sections are located at the southeast margin of the Sichuan Basin. A total of 1367 specimens were recovered, representing 30 species and 15 genera. Based on the ranges of conodonts generalized from these two sections and another six sections previously studied in the same region, three conodont zones, Cordylodus proavus, Monocostodus sevierensis and Cordylodus angulatus zones are recognized. The index species of the Cambrian–Ordovician boundary at the global stratotype section and point (GSSP), Iapetognathus fluctivagus and its substitute in China Iapetognathus jilinensis are not observed in the study sections, therefore it is impossible to determine the Cambrian–Ordovician boundary exactly. However, it probably lies within the lower part of M. sevierensis zone (the upper part of the Loushanguan Group), correlating with the GSSP in Canada and the Dayangcha section in China. Chronological sequences of the FAD (First Appearance Datum) of C. angulatus, Chosonodina herfurthi and Rossodus manitouensis are not obvious in the study, so the C. angulatus zone here is correlated with zones defined by C. angulatus, Ch. herfurthi and R. manitouensis in the lower Yangtze Platform.