贵州遵义高桥奥陶系湄潭组下部的笔石

对贵州遵义高桥大角寺剖面的奥陶系湄潭组下段和中段笔石的研究结果表明,湄潭组下段从下而上可以识别出Didymograptellus eobifidus带、Corymbograptellus deflexus带和Azygograptus suecicus带;中段含有一层笔石,缺少特征属种,根据其总体面貌,可能相当于Expansograptus hirundo带。文章描述其中11属16种:Pseudophyllograptus angustifolius(Hall),Phyllograptus claviger(Monsen),P.annaHall,Didymograptelluseobifidus(Chen and Xia),D.protoindentus(Monsen),Acrograptus kurcki(T rnquist),Corymbograptus vacil-lans(Tullberg,1880),C.deflexus(Elles and Wood),Expansograptus extensus(Hall),E.nitidus(Hall),Xi-phograptus lofuensis(Lee),X.cf.lofuensis(Lee),Azygograptus suecicusMoberg,Dictyonemasp.,Den-drograptussp.,Inocaulis plumulosusHall。这一笔石动物群分异度较低,大多数为上扬子区的常见属种,代表当时黔中古陆北缘近岸海洋环境中的笔石动物群面貌。     

安徽石台奥陶纪弗洛期—大坪期牙形刺多样性的演变

基于安徽石台栗阳柳树亭下、中奥陶统紫台组牙形刺的系统研究,对该地区早奥陶世弗洛期一中奥陶世大坪期牙形刺多样性演变作了初步分析,发现牙形刺的简单分异度在弗洛晚期Oepikodusevae带达到峰值,有17属20种。之后,牙形刺分异度呈下降趋势。演变的总体趋势与湖北宜昌地区同期牙形刺的研究结果一致,其峰值出现的时间（Oepikodusevae带,相当于笔石Didymograptellus eobifidus带上部,Corymbograptusdeflexus带,及Azygograptussuecicus带下部）与华南上扬子区腕足动物宏演化趋势（首次峰值出现在Didymograptelluseob—ifidus带）大体相似,但比三叶虫多样性演变在奥陶纪的首次峰值（出现在Exigraptus clavus带）早,比扬子台地笔石多样性演变的首次峰值（在Acrograptusfiliformis带和Didymograptelluseobifidus带下部）晚。分析显示,该地区早、中奥陶世牙形刺多样性演变与海平面变化存在密切关联。     

广东台山早奥陶世新厂组的笔石

本文记述了早奥陶世早期新厂组标准剖面的笔石动物群,分出了上下两个笔石带:上部clonograputs-Adelograptus 带和下部Staurograptus-Anisograptus 带,并与国内外相应笔石带进行了对比。文中描述了6属14种,其中4个新种。     

扬子北缘钟祥地区奥陶系弗洛阶笔石动物群研究

湖北钟祥下奥陶统弗洛阶岩性以灰黑色页岩为主,夹粉砂岩及灰岩透镜体, 化石丰度和分异度高。通过系统的化石采集和鉴定, 于钟祥温峡口剖面识别出笔石7属31种, 大体上为扬子地台区的常见属种。自下而上分为Didymograptellus bifidus带、Corymbograptus deflexus带和Azygograptus suecicus带。该序列与宜昌?南漳地区一致, 但在笔石动物群组成面貌上差异较大,可能与钟祥地区在早奥陶世位于扬子台地边缘, 富集的营养物质和低氧的环境更利于笔石动物群的繁盛和笔石化石的保存有关。     

上寒武统西伯利亚笔石(Siberiograptus)的发现

本文材料是1982年夏在山东沂南界湖和苍山大炉两地上寒武统凤山组中上部灰色、灰黄色薄层钙质、泥质白云岩中采得的。与所描述的西伯利亚笔石Siberiograptus共生的笔石有Callograptus和Dendrograptus两属大量树形笔石,其中除Callograptus staufferi Ruedemann和Dendrograptus hallianus(Prout)之外,均为区域性的新种。这一笔石动物群代表凤山组内一个     

加拿大北极地区泥盆纪叶肢介修订及兼论早期李氏叶肢介类(leaiins)的形态特征

湘南地区在晚奥陶世发育深水坳陷盆地相沉积, 完整记录了晚奥陶世桑比–凯迪期笔石页岩相生物地层序列。本论文在湘南地区祁东双家口 B 剖面开展笔石化石系统采集和生物地层学研究, 针对特征的江西笔石 (Jiangxigraptus)开展研究, 根据最新的分类学方案鉴定出江西笔石 1 属 6 种, 包括 Jiangxigraptus alabamensis (Ruedemann)、 Jiangxigraptus divaricatus (Hall)、 Jiangxigraptus gurleyi (Lapworth)、 Jiangxigraptus intortus (Lapworth)、Jiangxigraptus sextans (Hall)和 Jiangxigraptus vagus (Hadding)。此外, 本文还讨论了该属在全球范围内的分布, 认为在华南等地, Jiangxigraptus 可作为全球上奥陶统底界笔石生物地层对比的辅助属, 对识别上奥陶统桑比–凯迪阶的地层具有重要意义。     

湖南益阳早奥陶世弗洛期的笔石

本文报道湖南益阳南坝剖面早奥陶世弗洛期笔石16属30种,描述其中具有重要地层意义的笔石10属16种:Acrograptus affinis,A.gracilis,Baltograptus geometricus,B.vacillans,Clonograptus rigidus,Corym-bograptus deflexus,Cymatograptus undulatus,Didymograptellus bifidus,"Didymograptus"demissus,"D."rigo-letto,Expansograptus hol mi,E.constrictus,Pendeograptus fruticosus,P.pendens,Tetragraptus akzharensis,T.approxi matus。南坝剖面弗洛期笔石动物群以均分笔石为主,同时含有少量反称笔石。该地区弗洛期笔石动物群的分异度、丰度均较高,展示了笔石演化辐射早期斜坡相沉积环境下的笔石动物群特征。本文研究为全面理解奥陶纪笔石的演化辐射积累了重要资料。     

皖南、赣北早特马道克期Staurograptus的再研究

对皖南和赣北早奥陶世早特马道克期的Staurograptus重新研究表明,该属具有原始枝末端正分推迟、分支级数缩减和笔石枝密度降低的演化趋势,而代表不同演化阶段的三个种类,即Staurograptus dichotomus Emmons,S．apertus Ruedemann和S．hyperboreus Obut et Sobolevskaya,构成了该属基本的系统发育谱系。种群分析进一步显示,其主要性状变异范围尽管较宽但趋于正态分布的S．dichotomus,可能包含了除S．apertus和S．hyperboreus之外的所有已知Staurograptus的异名种类。     

川东南中奥陶统大沙坝组的腕足动物群

四川东南部长宁双河及其附近地区的中奥陶统上部大沙坝组以特殊的岩相和生物相有别于黔北的可比地层十字铺组和鄂西的牯牛潭组,地层中漂浮相化石(笔石)与底栖壳相化石(如腕足动物和三叶虫)多次交互出现,笔石动物属于上层下垂对笔石动物群(Didymograptus artus Fauna),时代为中奥陶世Darriwilian(相当于Arenig最晚期至Llanvirn)。在所采集的3300余枚化石标本中有近90％是腕足动物化石,经研究共鉴定出19属21种,分属于4目7超科15科,正形贝目和扭月贝目分别有8属,占全部属群的84％。根据属的生物地理分布,该动物群中广布型分子7属、区域性分子6属,仅限于华南的土著性分子占总量的31．6％,显示出此期华南腕足动物群具有较强的地方性色彩,进一步证实中奥陶世海洋生物强分区性的推断。该腕足动物群宜称作Saucrorthis-Glyptorthis动物群。在统计分析的基础上,识别出Saucrorthis-Glyptorthis群落,包括三个以腕足动物占优势的化石群集(association),即Glyptorthis?simplex群集、Saucrorthis obscura群集和Calyptolepta chengkouensis群集,并结合沉积岩石学以及其它共生化石门类进行群落生态分析,认为该群落所生活的环境以正常浅海砂泥质底域为主(相当于BA2-3)。与上扬子台地贵州遵义十字铺组和重庆城口厚坪组两个相近腕足动物群相比,长宁地区中奥陶世的Saucrorthis-Glyptorthis动物群更接近于厚坪组所产者。与世界上其它一些同期且具相似生态位的动物群相比,除与哈萨克斯坦南部的同期动物群比较接近外,与澳大利亚、北美、英国等地的同期动物群几乎毫无联系,指示华南中奥陶世腕足动物群可能代表一个独特的生物地理小区。     

运用数值分支学方法对皖南胡乐组双头笔石演化的研究

一、前言皖南中奥陶世胡乐组为黑色笔石页岩,所含笔石化石自下而上可分为3个笔石带:(1)Glyptograptus teretiusculus带;(2)Nemagraptus gracilis带;(3)Dicranograptus sinensis带。作为叉笔石动物群的重要组成分子,双头笔石开始出现于第1带,并于第2带和第3带获得了迅速分异和发展。皖南胡乐组双头笔石的研究始于本世纪30年代。许杰(1934)     

贵州思南奥陶纪末至志留纪初大息场组的笔石

贵州思南奥陶纪末至志留纪初大息场组的笔石研究结果表明,大息场组共产出笔石6属7种:Styracograptus chiai(Mu,1949),Normalograptus mirnyensis(Obut and Sobolevskaya,1967),Normalograptus ajjeri(Legrand,1977),Metaclimacograptus hughesi(Nicholson,1869),Avitograptus avitus(Davies,1929),Atavograptus atavus(Jones,1909)和Korenograptus laciniosus(Churkin and Carter,1970)。自下而上可识别出相当Dicellograptus complexus带、Akidograptus ascensus带和Cystograptus vesiculosus-Coronograptus cyphus带的3个含笔石地层带。虽然大息场组的笔石动物群分异度较低,但全都是上扬子区奥陶-志留系之交的常见属种,除S.chiai(Mu)之外,其它都是全球广布的物种。     

A relict Ordovician brachiopod fauna from the Parakidograptus acuminatus Biozone (lower Silurian) of the English Lake District

At Yewdale Beck in northern England, a brachiopod fauna dominated by species of Hindella, Kinnella, Mirorthis, Paromalomena and Plectothyrella , occurs interbedded with a graptolite fauna which includes Akidograptus ascensus , Atavograptus ceryx , Persculptograptus parvulus and Normalograptus spp. (including probable examples of N. normalis , N. angustus and N. medius ) within the lower part of the Skelgill Formation. This suggests that taxa of the terminal Ordovician Hirnantia fauna occur within the lower P. acuminatus Biozone, representing the youngest documented occurrence of the Hirnantia brachiopod fauna. Biostratigraphy, brachiopods, graptolites, Ordovician-Silurian boundary.     

Latest Ordovician graptolites from the Mandalay Region,Myanmar

The graptolite fauna of the Mandalay Region, Myanmar, is poorly known. In this paper, 13 species in the genera Avitograptus, Korenograptus, Metabolograptus, Neodiplograptus and Normalograptus are described from the uppermost Ordovician strata of the area. Two of these species, Korenograptus selectus X. Chen n. sp. and Neodiplograptus mandalayensis X. Chen n. sp., are new. On the basis of the graptolite faunas, a biostratigraphic scheme for the uppermost Ordovician (Hirnantian: Metabolograptus extraordinarius Biozone and Metabolograptus? persculptus Biozone?) strata in this area is erected.     

川西汉源-荥经地区下奥陶统大乘寺组的笔石

对川西汉源-荥经地区CYD2井下奥陶统弗洛阶大乘寺组的笔石进行研究,结果表明Baltograptus deflexus笔石带在这一覆盖区发育良好。CYD2井的该带笔石动物群共含2属5种。根据下垂对笔石类的始端发育型式,修正前人对波罗的笔石属(Baltograptus)和巅峰笔石属(Corymbograptus)内一些种的归属,并对CYD2井的5种笔石进行描述。可能受制于钻心标本的限制,该地区的Baltograptus deflexus带笔石动物群分异度较低。川西汉源-荥经-峨眉山地区的大乘寺组与上覆二叠系梁山组呈假整合接触,表明该地区长期遭受沉积间断和剥蚀作用,B.deflexus带的确定,指示了这一长期剥蚀作用的最大深度。     

Proposal for adoption of the base of the Undulograptus austrodentatus Biozone as a global Ordovician stage and series boundary level

The base of the Undulograptus austrodentatus Biozone appears to be a synchronous event that is widely recognizable within graptolitic facies around the world. It occurs within an interval in which graptolite species ranges are now well known and in which there is a rapid turnover in the composition of graptolite faunas. This turnover reflects the rapid evolutionary radiation of the Diplograptacea simultaneously with the appearance of several distinctive pseudisograptid and glossograptid species. These events provide the basis for the recognition of two thin but widely applicable subzones; a lower Arienigraptus zhejiangensis Subzone and an upper U. sinicus Subzone. The occurrence of the lower boundary of the U. austrodentatus Biozone within a succession of first appearances also permits accurate and reliable identification of the boundary as well as assessment of stratigraphic completeness across the boundary interval in correlated sections. Diverse graptolite faunas of late Yapeenian and early Darriwilian age occur in association with the Histiodella altifrons Biozone of the North American midcontinent conodont zonation and the Paroistodus originalis and Microzarkodina parva biozones of the North Atlantic conodont zonation. They also occur in association with the shelly-fossil zonations developed for several different continents. These features of the base of the U. austrodentatus Biozone make it a suitable level for use as the boundary level for a global stage. Its stratigraphic position within the Ordovician System relative to other likely global stages as well as its coincidence with one of the major events in graptolite evolutionary history suggest that this level also may be a suitable level for the base of a global Middle Ordovician Series.Ordovician System, Ordovician stages, graptolite zonation, chronostratigraphy, international correlation. Charles E. Mitchell and Jörg Maletz, Department of Geology, State University of New York at Buffalo, Buffalo, New York 14260-1550, USA; 13th July, 1994; revised 22nd May, 1995.     

HIRNANTIAN (LATEST ORDOVICIAN) GRAPTOLITES FROM THE UPPER YANGTZE REGION, CHINA

Abstract:  The Upper Yangtze region yields a Hirnantian (latest Ordovician) graptolite fauna that includes 41 species assigned to 13 genera. This fauna is particularly important for understanding the Late Ordovician mass extinction event because it is the most diverse known from this interval. In addition, it records the survival, well into the Hirnantian, of many taxa of the Dicranograptidae-Diplograptidae-Orthograptidae (DDO) fauna, which was previously regarded as having gone extinct at the beginning of the Hirnantian. Taxa exhibiting six different astogenetic patterns, including taxa with reclined stipes, scandent, biserial, full-periderm and 'archiretiolitid' rhabdosome forms occur in the lower Normalograptus extraordinarius-N. ojsuensis Biozone. In contrast, in the upper N. persculptus Biozone only four genera remain, all but one of which are Normalograptidae: scandent and biserial taxa with Pattern H astogeny. Normalograptids are the dominant form of the succeeding, lower Rhuddanian, faunas. The Yangtze faunas also document the early expansion of normalograptids coeval with the decline of the DDO fauna. Many previously identified species considered endemic to China have been synonymized; 24 of the 41 species recorded here have been recognized elsewhere. No new taxa are described.     

The latest Ordovician Hirnantia Fauna (Brachiopoda) in time and space

The diachronous temporal and spatial distribution of the Hirnantia brachiopod fauna and the complicated pattern of terminal Ordovician events are documented through biostratigraphical analysis of the Ordovician-Silurian boundary strata in S China, Sibumasu, Xizang and elsewhere. The duration of these events (longer than the half Myr derived from isotopic excursions) indicates that they were not abrupt and instantaneous. The presence of some core taxa of the Hirnantia fauna in the upper P. pacificus Biozone (known from their earliest occurrence in China) signals the start of increased water ventilation due to the invasion of cool water across the Yangtze Basin. Low- and higher-diversity Hirnantia faunas related to onshore, shallow-water and to offshore, deeper-water environments, respectively, developed first in the basal and upper N. extraordinarius-N. ojsuensis Biozone. Disappearance of most of the fauna in the early N. persculptus Biozone suggests that the glacial maximum started to decline. The presence of the Hirnantia fauna in the upper N. persculptus to the lower P. acuminatus biozones indicates the continuation of cool water environments in some places. The diachronous disappearance of deteriorating environments (earlier in later Hirnantian and finally in the early Rhuddanian) is associated with geographical heterogeneity. Occurrences of atrypids, pentamerids and spiriferids along with key elements of the Hirnantia fauna in N Guizhou provide a link between the Late Ordovician radiation and Early Silurian recovery of these major brachiopod groups.     

Volkhov graptolites from the lower-middle Ordovician boundary beds of the St. Petersburg region,Russia

The lower and lowermost Middle Ordovician strata of the Volkhov Stage exposed in the vicinity of St. Petersburg, Russia, yield a graptolite fauna at several stratigraphic levels, being more often confined to the mud-mound clays than to the normally stratified, Condensed carbonates. Overall taxonomic diversity of the Volkhov graptolites is relatively low and associations include no more than seven species in ail localities. TheTetragraptus, Didymograptus andXiphograptus species found are pandemic and have quite extensive stratigraphie ranges within the mid-Arenig Series. Based on the graptolite zonation, the Volkhov Stage can be correlated to thePseudophyllograptus angustifolius elongatus andDidymograptus (Expansograptus) hirundo graptolite biozones of Baltoscandia and to the upperDidymograptus simulans toDidymograptus (Expansograptus) hirundo biozones of the British graptolite succession. TheIsograptus victoriae lunatus lower zonal boundary probably falls within the graptolite-bearing interval of the lower Volkhov Stage. As the result of indirect biostratigraphic and interpretative lithological correlations, the first appearance ofUndulograptus austrodentatus at the base of the Darriwilian Stage is deemed to be close to the boundary of theMegistaspis simon andM. limbata trilobite biozones and the lowerBaltionodus norrlandicus conodont Biozone of the upper Volkhov Stage. Seven dichograptid species belonging to four genera are described, one of them,Azygograptus volkhovensis n. sp., new.      

The Lerhamn drill core and its bearing for the graptolite biostratigraphy of the Ordovician Tøyen Shale in Scania,southern Sweden

Maletz, J. & Ahlberg, P. 2011: The Lerhamn drill core and its bearing for the graptolite biostratigraphy of the Ordovician Tøyen Shale in Scania, southern Sweden. Lethaia, Vol. 44, pp. 350–368. A drill core through the Lower Ordovician Tøyen Shale Formation at Lerhamn, NW Scania, southern Sweden, provides important new information for the precise biostratigraphic resolution of the Floian to lower Darriwilian time interval in southern Scandinavia. The Hunnegraptus copiosus, Tetragraptus phyllograptoides, Cymatograptus protobalticus (new), Baltograptus vacillans (new), Baltograptus sp. cf. Baltograptus deflexus (new), Baltograptus minutus (new), Isograptus victoriae, Undulograptus austrodentatus (Arienigraptus zhejiangensis and Undulograptus sinicus Subzones) and the (?)Corymbograptus retroflexus (new) biozones are differentiated in the core and their correlation in Scania is discussed. The Lerhamn drill core provides the most detailed graptolite record of the Floian Stage in Scandinavia. The interval is dominated by a number of species of the genus Baltograptus, endemic to the Atlantic Faunal realm and highly useful for regional biostratigraphic correlation. The biostratigraphic framework is based on endemic and pandemic faunal elements. The mixture of both elements in the drill core allows a more precise inter‐continental correlation of Lower to Middle Ordovician graptolite faunas and may – in the future – provide information as to the climatic history of regions dominated by Baltograptus faunas in the Floian. The (?)C. retroflexus Biozone is based on species originally described from Bohemia, but the record of the zone in the Lerhamn drill core indicates a wider distribution of its fauna. □Biostratigraphy, graptolites, Ordovician, Scania, Sweden.