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.     

Stage boundaries of the Triassic in Northeast Asia

The International Union of Geological Science approved the stage boundaries suggested by the international working groups for the Tethyan Triassic. In this work we estimate the possibility of their establishment and correlation in the Boreal sections of Northeast Asia, based on the analyzed distribution of ammonoids and conodonts. As the conodonts of the Induan Stage have not been identified for sure in the region under study, the lower boundary of the Triassic System is defined here at the base of the Otoceras concavum Zone of the ammonoid scale. In addition to the ammonoids Hedenstroemia hedenstroemi (Keyserling), the first occurrence of the conodonts Pseudogondolella nepalensis (Kozur et Mostler) is suggested to be the biomarker of the Olenekian Stage base. The lower boundaries of the Anisian and Ladinian stages, defined respectively at the basal levels of the Paracrochordiceras-Japonites Beds in Northern Dobrogea and the Eoprotrachyceras curionii Zone in the Brescian Prealps are recognizable, though with some reservations, at the base of the Grambergia taimyrensis and Eonathorstites oleshkoi zones in Northeast Asia. According to the priority principle and similarity between the ammonoid faunas of the Daxatina cf. canadensis Subzone and Frankites regoledanus Zone, the lower boundary of the Carnian Stage is defined at the base of the Alpine Trachyceras aon Zone. In Northeast Asia, this boundary is established at the base of the “Protrachyceras” omkutchanicum Zone, as we take into account the fact that the Daxatina and Stolleyites ammonoid genera occur in sections of British Columbia below the stratigraphic level of the Trachyceras forms. The lower boundary of the Norian Stage is concurrent with the base of the Guembelites jandianus Zone in the Alps and equivalent Stikinoceras kerri Zone in North America and Striatosirenites kinasovi Zone in Northeast Asia. The conodont species Norigondolella navicula (Huckriede) that is most important for the Boreal-Tethyan correlation cannot be used as a biomarker of the Norian lower boundary because of its problematic diagnosis and rare occurrence in the Boreal sections. The Rhaetian Stage base is defined at the appearance level of the Misikella conodont genus in the Hallstatt region, Austria, that is simultaneously the disappearance level of the characteristic Norian bivalves (Monotis) and ammonoids (Metasibirites). In Northeast Asia, this boundary is established at the top of the Monotis ochotica Zone. The correlation between the biostratigraphic units of the Middle-Upper Triassic conodont scale established in Northeast Asia and standard ammonoid zonation is verified.     

Early Triassic (Induan–Olenekian) conodont biostratigraphy,global anoxia,carbon isotope excursions and environmental perturbations: New data from Western Australian Gondwana

The Early Triassic Induan–Olenekian Stage boundary (Dienerian–Smithian sub-stage boundary) has been identified at a depth of 2719.25 m in the petroleum exploration well Senecio-1 located in the northern Perth Basin, Western Australia. Conodont faunas represent three conodont zones in ascending order, the Neospathodus dieneri Zone, the Neospathodus waageni eowaageni Zone and the Neospathodus waageni waageni Zone. The Induan–Olenekian (Dienerian–Smithian) boundary is placed at the base of the Neospathodus waageni eowaageni Zone equivalent to the first appearance of Neospathodus ex. gr. waageni utilised elsewhere and adopted by the IUGS ICS Triassic Subcommission to define the base of the Olenekian. Bulk kerogen δ¹³C carbon isotopes define a positive peak of c. 4 per mille that essentially coincides with the Induan–Olenekian boundary as seen in proposed Global Stratotype Sections and Points (GSSPs) in South China and Spiti, India demonstrating the global utility of this level for correlation. An anoxic zone is recognised in the lower part of the Senecio-1 core and the upper limit of this zone is dated as late Induan (late Dienerian). Temporal and spatial mapping of marine anoxia and dysoxia globally demonstrates that pulses of dysoxia/anoxia affected shallow-marine zones at different times in different locations. Dysoxia/anoxia in the shallow-marine environment appeared in the latest Permian at the extinction level, later than in the deep-marine environment, and appears to be largely restricted to the Induan (Griesbachian and Dienerian) and early Olenekian (Smithian). Temporally and geographically restricted upwelling of an oxygen minimum zone into the ocean surface layer due to environmental perturbations including extreme global warming, increased terrestrial chemical weathering intensity and continental erosion, sea level rise, and changes in marine nutrient inventories and productivity rates, is interpreted as a likely cause of observed variation in shallow-marine dysoxia/anoxia in the Early Triassic.     

Restudy of conodont biostratigraphy of the Permian–Triassic boundary section in Zhongzhai,southwestern Guizhou Province,South China

New conodont samples have been systematically collected at high stratigraphic resolution from the upper part of the Longtan Formation through to the lower part of the Yelang Formation at the Zhongzhai section, southwestern Guizhou Province, South China, in an effort to verify the first local occurrence of Hindeodus parvus in relation to the Permian–Triassic boundary at this section. The resampled conodont fauna from the Permian–Triassic boundary interval comprises five identified species and two undetermined species in Hindeodus and Clarkina. Most importantly, the first local occurrence of Hindeodus parvus is found for the first time from the bottom of Bed 28a, 18 cm lower than the previously reported first local occurrence of this species at this section. Considering the previously accepted PTB at the Zhongzhai section, well calibrated by conodont biostratigraphy, geochronology and carbon isotope chemostratigraphy, this lower (earlier) occurrence of H. parvus suggests that this critical species could occur below the Permian–Triassic boundary. As such, this paper provides evidence that (1) the first local occurrences of H. parvus are diachronous in different sections with respect to the PTB defined by the First Appearance Datum (FAD) of this species at its GSSP section in Meishan, China and that (2) the lower stratigraphic range of H. parvus should now be extended to latest Permian.     

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...     

Current perspectives on the Permian–Triassic boundary and end-Permian mass extinction: Preface

The end-Permian mass extinction is now robustly dated at 252.6 ± 0.2 Ma (U–Pb) and the Permian–Triassic (P–T) GSSP level is dated by interpolation at 252.5 Ma. An isotopic geochronological timescale for the Late Permian–Early Triassic, based on recent accurate high-precision U–Pb single zircon dating of volcanic ashes, together with calibrated conodont zonation schemes, is presented. The duration of the Early Triassic (Induan + Olenekian stages) is estimated at only 5.5 million years. The duration of the Induan Stage (Griesbachian + Dienerian sub-stages) is estimated at ca. one million years and the early Olenekian (Smithian sub-stage) at 0.7 million years duration. Considering this timescale, the “delayed” recovery following the end-Permian mass extinction may not in fact have been particularly protracted, in the light of the severity of the extinction. Conodonts evolved rapidly in the first 1 million years following the mass extinction leading to recognition of high-resolution conodont zones. Continued episodic global environmental and climatic stress following the extinction is recognized by multiple carbon isotope excursions, further faunal turnover and peculiar sedimentary and biotic facies (e.g. microbialites). The end-Permian mass extinction is interpreted to be synchronous globally and between marine and non-marine environments. The nature of the double-phased Late Permian extinction (at the Guadalupian–Lopingian boundary and the P–T boundary), linked to large igneous provinces, suggests a primary role for superplume activity that involved geomagnetic polarity change and massive volcanism.     

安徽巢湖地区下三叠统牙形石生物地层分带及其全球对比

安徽巢湖地区早三叠世处于下扬子碳酸盐岩缓坡较深水区域,地层序列完整、清晰,各类化石是区域乃至全球最为丰富、序列最为完整的,是研究国际早三叠世年代地层最经典地区之一．对安徽巢湖平顶山西坡剖面、平顶山北坡剖面、马家山南剖面系统采样和精细的牙形石生物地层研究结果表明,下三叠统至少可以划分为8个牙形石带,建立了在华南具有代表性的下三叠统牙形石生物地层序列,自下而上为（1）Hindeodus typicalis带;（2）Neogondolella krystyni-Neogondolella planata带;（3）Neospathodus kummeli带;（4）Neospathodus dieneri带;（5）Neospathodus iaageni带;（6）Neospathodus pingdingshanensis带;（7）Neospathodus homeri带;（8）Neospathodus anhuinensis带．并与世界其他地区同期地层进行精确对比,为建立下三叠统印度阶与奥伦尼克阶界线的全球层型（GSSP）提供可靠依据．     

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.     

浙江长兴煤山地区吴家坪阶-长兴阶界线地层的再认识

浙江长兴煤山的 D剖面经多年研究 ,已成为二叠系长兴阶的单位层型和二叠系 -三叠系全球界线层型 ,并被推荐为吴家坪阶 -长兴阶全球界线层型的候选剖面 ,因该剖面上龙潭组地层出露较少 ,以致国内对长兴组与龙潭组的接触关系存有不同意见 ,给层型剖面的建立带来不利影响。在清理和研究了 D剖面西侧 30 0 m处 C剖面的吴家坪阶 -长兴阶界线层段后 ,证实了煤山地区龙潭组与长兴组为整合接触 ,对相关化石的地层分布也获得进一步的认识     

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。     

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.     

中国奥陶系和下志留统下部年代地层单位的划分

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?     

Global correlations of mid Early Triassic events: The Induan/Olenekian boundary in the Dolomites (Italy)

The Dolomites (Southern Alps, Italy) are a reference-area for research on the end-Permian mass extinction and its Early Triassic aftermath. The effects on shallow marine benthic biota are recorded in the Werfen Formation, a thick mixed carbonate-siliciclastic sedimentary succession. Only in its lower (Griesbachian) and upper (Spathian) parts, this formation is bio-chronologically constrained by means of conodonts and ammonoids, whilst no significant bioevent occurs in its middle part. This represents an impediment to the biochronologic recognition of the Induan/Olenekian boundary (IOB).The Bulla/Pufels (Val Gardena) succession is a key-section for the P/T boundary and Early Triassic for global correlation due to the abundance of studies on biostratigraphy (mostly on conodonts), magnetostratigraphy and chemostratigraphy carried out there by stratigraphers of various nationalities. Recent chemostratigraphic studies have permitted the recognition of some carbon isotope positive peaks, the strongest of which is considered to approximate the IOB. However, various authors have reached different conclusions on the position of the maximum peak and thus on the IOB location. This leads to important stratigraphic consequences for the calibration of conodont biostratigraphy. The critical revision of the traditional stratigraphic units (litho- and biostratigraphy), under-evaluated in most of the recent literature, and magneto-, chemo- and sequence stratigraphic units allowed herein an integrated stratigraphic scale for the Bulla/Pufels section to be proposed. This contribution highlights the mid Early Triassic Dolomites record for regional and global correlations.The most significant results attained herein regard the different lithostratigraphic subdivisions of the middle Werfen Formation and its consequences on the position of the IOB with respect to the conodont and bivalve biostratigraphy and sequence stratigraphic units. The upper part of the section is attributed herein to the Gastropod Oolite Member, which is represented by the lithozone A, a predominant supratidal episode, and the lower part of the subtidal lithozone B. Between the lithozones A and B, a sequence boundary of 3th order (Sc2/Sc3) is located. The maximum carbon isotope excursion is near this boundary, which therefore approximates the IOB in the Dolomites. This proposal suggests a Dienerian age for the FO of the conodont Pachycladina obliqua, which occurs about 60 m below the stage boundary. No significant biotic event, either for molluscs or conodonts, occurred across this stage boundary.     

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。     

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。     

新近系保德阶建阶研究新进展

根据与古地磁极性年表的对比 ,山西保德冀家沟剖面含保德动物群的保德组上界年龄为 5 .30 Ma,底界年龄不超过 10 Ma,其红黏土的底界为 8Ma,显示该剖面不存在定义的保德阶 11.2 Ma的下界 ,也没有保存保德阶下部的沉积。《国际地层指南》提倡用选择下界的界线层型来确定年代地层单位 ,其上界应该由后续单位的下界来确定。冀家沟剖面显然不具备保德阶的下界 ,但甘肃临夏盆地郭泥沟剖面含三趾马动物群的红黏土之下还有发育的中中新世沉积出露 ,因此 ,后一个地点应存在保德阶的下界 ,并有保德阶最底部的化石和适合于作古地磁分析的沉积物 ,所以临夏盆地是一个有可能建立保德阶下界界线层型的有利地点     

Stratigraphy of the Middle Devonian boundary: Formal definition of the susceptibility magnetostratotype in Germany with comparisons to sections in the Czech Republic, Morocco and Spain

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.     

“Sub-Triticites Beds” of the Donskaya Luka and lower boundary of the Kasimovian Stage

Micro- and macrofauna remains were studied from transitional deposits of Moscovian and Kasimovian Stages in the Donskaya Luka (Volgograd Region). The preliminary analysis of microfauna showed that “sub-Triticites Beds” of the Donskaya Luka contain fusulinid and conodont assemblages enabling correlation of the Middle and Upper Carboniferous deposits in the study region with the type sections of Moscow area and Donbass. Conodonts from the “sub-Triticites Beds” stratotype were studied for the first time. As is established, upper part of the Sukhov Fm. and the base of the Seleznev Fm. belong to the Protriticites pseudomontiparus-Obsoletes obsoletus Zone. Based on fusulinids, higher parts of the Seleznev Fm. belong to the Montiparus Zone of the Khamovnikian Substage, whereas conodonts suggest their correlation with lower part of the Khamovnikian Substage, i.e., with the Ratmirovo Fm. or a basal part of the Neverovo Fm. Middle part of the Seleznev Fm. is correlated to middle cycle of the Neverovo Fm. of the Khamovnikian Substage in Moscow area. The Middle-Upper Carboniferous boundary deposits of the Donskaya Luka are represented by deposits of extremely shallow-water settings and contain only sporadic microfauna. These sections cannot be considered as possible candidates for the GSSP of the Kasimovian Stage base.     

论中国的石炭系与二叠系界线

国际地层委员会确认二叠系下界以牙形刺 Streptognathodus isolatus的首次出现为标志。目前在我国 ,S.isolatus仅见于贵州紫云羊场一地 ,产出层位介于 Streptognathodus elegantulus带与 S.elongatus- S.simplex带之间的界面 ,且大体与类 Pseudoschwagerina uddeni- Ps.texana带之底相当。本文推荐贵州紫云羊场剖面作为我国的石炭系与二叠系界线层型。     

The Serpukhovian Stage in the Verkhnyaya Kardailovka section,South Urals

The paper describes a Serpukhovian Stage section, exposed along the Ural River near the village of Verkhnyaya Kardailovka (Bashkortostan). The section is uniquely complete and is proposed as a GSSP candidate for the base of the Serpukhovian. The Upper Visean and Serpukhovian beds are represented by relatively deep facies, which contain ammonoids, conodonts, ostracods, foraminifers, and other fossils. The section is described bed-by-bed and subdivided into zones based on four faunal groups. The lower boundary of the Serpukhovian is placed at the base of the Lochriea ziegleri conodont zone. The stratigraphic units are correlated with synchronous beds of the East European Platform, the Donets Basin, Western Europe, Central Asia, and North America.