湖北宜昌地区下-中奥陶统界线疑源类生物地层学意义

根据牙形类Baltoniodus? triangularis的首现,中奥陶统和大坪阶底界已界定于湖北宜昌黄花场剖面大湾组底界之上10.57m.对黄花场剖面以及邻近的大坪剖面大湾组疑源类研究表明,某些疑源类属种具有生物地层学意义,其首现可用于识别奥陶系下/中统界线.     

湖北宜昌黄花场剖面中/下奥陶统界线附近的牙形剌

重点描述宜昌黄花场剖面中 /下奥陶统界线附近的重要牙形剌共 3属、5种和 2新种Bergstroe mognathussp .nov .,BaltoniodustetrachotomusLiandWangsp .nov .,并对Oepikodusevae带和Baltoniodustriangu laris带分子的首现位置及带的含义进行厘定。作者还在此剖面大湾组下段发现北美中大陆区暖水型牙形剌Tripoduslaevis和Protoprioniodusaranda ,并确定Tripoduslaevis的首现位置在Baltoniodustriangularis带底界之上 0 .3m处。Tripoduslaevis的首次出现曾提议为中奥陶统的底界的标志 (见陈旭等 ,2 0 0 0 ) ,在宜昌黄花场剖面上Tripoduslaevis的首现位置接近Baltoniodustriangularis带底界 ,对确定中 /下奥陶统界线很重要。由于在黄花场剖面可识别出Baltonioduscrassulus—B .gladiatus—B .triangularis演化谱系 ,作者建议以B .triangularis的首次出现作为中奥陶统的底界 ,宜昌黄花场剖面为中 /下奥陶统界线的层型剖面。同时 ,文中将本区的牙形刺带与世界其它地区作了对比。     

湖北宜昌黄花场下奥陶统弗洛阶Oepikodus evae带精细地层划分对比

全球中奥陶统及奥陶系第三个阶、大坪阶的界线层型剖面和点位(GSSP)确定后,文中作者对宜昌黄花场剖面弗洛阶上部Oepikodus evae带牙形刺生物地层序列进行再研究。通过对红花园组上部-大湾组下段一些关键层位中牙形刺样品的补充采集和牙形刺标本的系统检查,研究牙形刺属种垂向分布特征,修订一些牙形刺属种的首现层位。讨论Stolodus stola,Lundodus gladiatus,Oepikodus intermedius,Oepikodus communis,Trape-zognathus diprion,Baltonioduscf.B.triangularis等重要的多分子器官种分类问题。识别出Baltoniodus trian-gularis(Lindstr m)的先驱:Baltonioduscf.B.triangularis(Lindstr m)与Baltoniodus triangularis(Lindstr m)的区别。描述新建化石带属种,包括Baltoniodus triangularis(Lindstr m)。认为Oepikodus evae带上部时限范围内并未见Oepikodus evae分子,所以与国际地层指南(2000)关于间隔带和延限带的含义相悖。据此,厘定了原Oepikodus evae带的含义。并以牙形刺带分子首现为标志,将大湾组下段自下而上划分为3个间隔带,分别为:O.evae带,Trapezognathus diprion带和Baltonioduscf.B.triangularis带。其中Trapezognathus diprion带和Baltonioduscf.B.triangularis带为新建化石带。     

安徽石台下、中奥陶统紫台组的牙形刺

下、中奥陶统紫台组以紫红色泥质灰岩、瘤状泥质灰岩为特征,具有稳定的空间分布范围,沿扬子台地东南缘呈条带状分布,与扬子台地上发育的湄潭组、大湾组等大致同期。作者研究了安徽石台栗阳柳树亭剖面紫台组的牙形刺,共描述19属23种,识别出四个牙形刺带,从下至上分别是Oepikodus evae带、Baltoniodus triangularis带、Baltoniodus navis带和Paroistodus originalis带,并可与同期笔石带对比。除扬子区外,紫台组还可与欧洲、阿根廷前科迪勒拉等地区的同期地层对比。     

重庆城口大塘口下奥陶统红花园组和湄潭组下部的几丁虫

文中图示和描述了重庆城口大塘口奥陶系红花园组和湄潭组下部营盘段的几丁虫计 6属, 17种。其中包括 7个未定种和 3个新种 (Conochitinadatangkouensissp. nov., C. wengxigouensissp. nov., Rhabdochitinachenk ouensesp. nov. )。讨论了几丁虫的地理和地层分布特点及其与笔石生物带的关系,阐明了红花园组和湄潭组下部营盘段不同笔石带(A. filiformis, D. bifidus和A. suecicus笔石带)中几丁虫的组合特征,并与国外同期地层几丁虫组合进行了对比。     

山东省青州地区寒武-奥陶系界线研究的新进展

首次报道了山东省青州地区尧王山剖面的寒武 奥陶系界线地层的牙形石生物地层学的最新研究成果,在该剖面的炒米店组灰岩建立了 9个牙形石带,其中下奥陶统为 3个带,上寒武统凤山阶为 6个带;并与国内外研究较详细的寒武 奥陶系界线地层进行了对比。在该剖面首次发现了界线牙形石分子Iapetognathusfluctivagus,这也是在整个华北地区的首次报道,这一发现为山东地区乃至整个华北地区的寒武 奥陶系的界线划分提供了新的标尺。     

鄂西、黔南下奥陶统大湾组中的笔石

一、前言1956年笔者和钱义元、朱兆玲、陈楚震、张守信等同志随同张文堂先生在湖北西部宜昌,秭归一带调查时,在大湾组(狭义的大湾组)下部采得一些下奥陶统的笔石。1957年笔者和葛梅钰等同志随同王钰、穆恩之二先生又到湖北西部宜昌、秭归一带调查,除在大湾组下部又获得许多笔石外,并在大湾组上部获得下奥陶统上部的笔石,1959年笔者和李蔚秾、张树森等同志在贵州南部都匀、麻江一带调查时,亦发现和大湾组相同的地层,     

全球界线层型华南浙江长兴煤山剖面牙形石序列研究进展

华南浙江长兴煤山剖面是全球两个金钉子点位(全球二叠系一三叠系界线层型及点和全球吴家坪阶一长兴阶界线层型及点)定位的GSSP剖面.煤山剖面上二叠统一下三叠统自下向上依次为龙潭组顶部、长兴组、殷坑组、和龙山组及南陵湖组下部.文中综合近30年来国内外学者对煤山剖面牙形石研究成果,将该削面晚二叠世一早三叠世牙形石序列自下而上归纳为13个牙形石带,分别为:1)Neogondolella orientalis-Neogondolella longi-cuspidata带(龙潭组顶部一长兴组底部:第1层-4a-1层);2)Neogondolella wangi带(长兴组下部:第4a-2层-10层),其首现点标定了国际长兴阶底界金钉子点位;3)Neogondolella changxingensis-Neogondolella deflecta带(长兴组上部:第11层-23层);4)Neogondolella yini-N.zhangi带(长兴组顶部:P/T界线层第24层);5)Neogondolella meishanensis带(殷坑组底部:P/T界线层第25层);6)Hindeodus changxingensis带(殷坑组底部:P/T界线层第26层);7)N.taylorae带(殷坑组底部:P/T界线层第27a层-27b层);8)Hindeodus parvus 带(殷坑组底部:P/T界线层第27c层),其首现点标定了国际三叠系底界金钉子点位;9)Isarcicella staeschei带(殷坑组底部:P/T界线层第27d层-29a层);10)Isarcicella isarcica带(殷坑组下部一中部:第29b层-51层);11)Neogondolellatulongensis-Neogondolella planata带(殷坑组上部一和龙山组下部:第52层-72层);12)Neo-spathodus kummeli带(和龙山组中部:第73层-92层);13)Neospathodus cristagalli-Neospathodus dieneri带(和龙山组上部一南陵湖组下部:第93层-111层).同时,为了提高全球不同地区二叠系-三叠系界线牙形石对比精度,文中也讨论并修改了该剖面二叠纪-三叠纪之交hindeollid型与gondolellid型平行的牙形石带.     

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。     

中国宜昌王家湾晚奥陶世五峰组几丁虫的初步研究

中国宜昌王家湾北剖面已被提名为奥陶系赫南特阶的全球候选层型剖面。为此著者分析了王家湾地区,特别是王家湾南和王家湾小河边奥陶—志留系间相关地层共20个层位的几丁虫样品。初步研究的结果表明,王家湾赫南特阶之下,相当奥陶纪第6个阶顶部,即五峰组中部产出的几丁虫与美国内华达中部Vnini河谷以及加拿大极区Cape Mannig的Ordochitina nevadensis 和Nevadachitina vininica 几丁虫带的分子可以进行对比。     

新疆柯坪和甘肃平凉上奥陶统底部附近的牙形刺

新疆柯坪大湾沟和甘肃平凉官司庄剖面是Nemagraptusb gracilis带及上奥陶统底界的重要剖面,研究这两剖面的牙形刺具有十分重要的意义。本文描述了采自新疆柯坪大湾沟和甘肃平凉官司庄剖面上奥陶统底界附近的牙形刺共13属18种。     

Middle and Upper Cambrian Protoconodonts and Paraconodonts from Hunan, South China

More than 4200 kg of limestone, representing 980 productive samples, from the upper Middle Cambrian, Upper Cambrian, and lowermost Ordovician in western and north-western Hunan were processed for paraconodonts, protoconodonts, and euconodonts. The focus of the present paper is on the upper Middle and lower Upper Cambrian interval as it is developed at two, apparently stratigraphically continuous, key sections. The collections studied, which include more than 20,000 specimens and are quite diverse taxonomically, prove that some protoconodonts and paraconodonts are useful biostratigraphically. Previously proposed protoconodont-paraconodont biozones in Hunan are revised and correlated with recently revised trilobite biozones, as well as with protoconodont-paraconodont and trilobite biozones in North China. Twenty-six species and seven conditionally identified species belonging to 13 genera are described. Among these, two genera ( Huayuanodontus and Yongshunella ) and two species ( Westergaardodina elegans and Yongshunella polymorpha ) are new. This study has special interest for Cambrian biostratigraphy because the two studied sections are global stratotype candidates for the Middle-Upper Cambrian series boundary. The level of the Upper-Middle Cambrian Series boundary, as currently recognized in China (at the base of the Linguagnostus reconditus Trilobite Biozone) is well marked in the paraconodont succession and can be traced into the Swedish standard succession using these fossils. By contrast, another level recently proposed as a potential global Middle-Upper Cambrian Series boundary level, the base of the Glyptagnostus reticulatus Trilobite Biozone, does not coincide with any marked change in the Hunan conodont species succession useful for local and regional correlation.     

Re‐evaluation of the conodont Iapetognathus and implications for the base of the Ordovician System GSSP

Terfelt, F, Bagnoli, G. & Stouge, S. 2011: Re‐evaluation of the conodont Iapetognathus and implications for the base of the Ordovician System GSSP. Lethaia, Vol. 45, pp. 227–237. In 2000, the International Union of Geological Sciences (IUGS) ratified the decision from the International Working Group on the Cambrian–Ordovician Boundary (COBWG) to place the Global boundary Stratotype Section and Point (GSSP) for the base of the Ordovician System in the Green Point section, Newfoundland, Canada, at a point coinciding with the first appearance of the conodont Iapetognathus fluctivagus. However, a restudy of the conodont successions from Green Point shows that this species is not present at the boundary interval, and as a consequence the section does not fulfil the biostratigraphical requirements of a GSSP. The GSSP horizon as now defined is based on a level part‐way through the range of I. preaengensis– a species with lower first appearance datum (FAD). The true FAD of I. fluctivagus is above the FAD of planktonic graptolites and well above the FAD of I. preaengensis. As a consequence of these problems, a restudy of the GSSP section and the other sections in the Cow Head Group is necessary. A redefinition of the GSSP horizon is suggested. The following four alternative horizons have potential as new horizons for the GSSP level: the FAD of Cordylodus intermedius; the FAD of Cordylodus andresi; the FAD of Eoconodontus notchpeakensis; and the FAD of the agnostoid Lotagnostus americanus. □Boundary, Cambrian, conodont, Global boundary Stratotype Section Point, Iapetognathus, Ordovician.     

Global Standard Stratotype-section and Point (GSSP) of the Furongian Series and Paibian Stage (Cambrian)

The Global Standard Stratotype-section and Point (GSSP) of the Furongian Series (uppermost series of the Cambrian System) and the Paibian Stage (lowermost stage of the Furongian Series), has been recently defined and ratified by the International Union of Geological Sciences (IUGS). The boundary stratotype is 369 metres above the base of the Huaqiao Formation in the Paibi section, northwestern Hunan Province, China. This point coincides with the first appearance of the cosmopolitan agnostoid trilobite Glyptagnostus reticulatus, and occurs near the base of a large positive carbon isotopic excursion (SPICE excursion).     

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.     

Proposed stratotype for the base of the highest Cambrian stage at the first appearance datum of Cordylodus andresi, Lawson Cove section, Utah, USA

We propose a candidate for the Global Standard Stratotype-section and Point (GSSP) for the base of the highest stage of the Furongian Series of the Cambrian System. The section is at Lawson Cove in the Ibex area of Millard County, Utah, USA. The marker horizon is the first appearance datum (FAD) of the conodont Cordylodus andresi Viira et Sergeyeva in Kaljo et al. [Kaljo, D., Borovko, N., Heinsalu, H., Khazanovich, K., Mens, K., Popov, L., Sergeyeva, S., Sobolevskaya, R., Viira, V., 1986. The Cambrian–Ordovician boundary in the Baltic–Ladoga clint area (North Estonia and Leningrad Region, USSR). Eesti NSV Teaduste Akadeemia Toimetised. Geologia 35, 97–108]. At this section and elsewhere this horizon also is the FAD of the trilobite Eurekia apopsis (Winston et Nicholls, 1967). This conodont characterizes the base of the Cordylodus proavus Zone, which has been recognized in many parts of the world. This trilobite characterizes the base of the Eurekia apopsis Zone, which has been recognized in many parts of North America. The proposed boundary is 46.7 m above the base of the Lava Dam Member of the Notch Peak Formation at the Lawson Cove section. Brachiopods, sequence stratigraphy, and carbon-isotope geochemistry are other tools that characterize this horizon and allow it to be recognized in other areas.     

The base of the Middle Ordovician in China with special reference to the succession at Hengtang near Jiangshan, Zhejiang Province, southern China

Extensive work during the last decade has led to the recent decision by the International Subcommission on Ordovician Stratigraphy that the base of the Middle Ordovician Series should be placed at the base of the Baltoniodus triangularis Conodont Biozone in the Huanghuachang GSSP (Global Stratotype Section and Point) section near Yichang, Hubei Province, China. A review of the biostratigraphy of successions in many parts of China shows that for various reasons, it is currently difficult to recognize the precise boundary level in many regions, and additional studies are clearly needed. A newly exposed, previously poorly known, condensed section in deeperwater facies at Hengtang near Jiangshan in the Chiangnan (Jiangnan) belt has yielded a substantial number of important graptolites and conodonts through the boundary interval. It provides a more informative illustration of the relations between the ranges of several key taxa of these groups than any other section in China, and the level of the base of the Middle Ordovician appears to be within an about 1.8 m thick interval of Ningkuo Formation, and lies in the lower Isograptus caduceus imitatus Biozone.     

华中西南区一条国际前寒武系与寒武系界线层型补充剖面

1992年,全球前寒武系与寒武系界线层型剖面和层型点确定在加拿大纽芬兰东南幸运角剖面,并以遗迹化石带Trichophycus pedium的底作为前寒武系与寒武系的分界点。但是,幸运角剖面主要是以硅质碎屑岩相为主,难以与含有丰富小壳化石和具有可对比的稳定同位素资料的碳酸盐相界线剖面进行对比。为此,提出我国云南会泽大海附近的一条以碳酸盐相为主的剖面作为全球前寒武系与寒武系界线层型剖面的补充剖面。理由是（1）在大海剖面上,震旦系灯影组白岩哨段、待补段和下寒武统牛家菁组的中谊村段,大海段之间为整合接触;（2）早寒武世早期地层单元含有丰富的小壳化石并且可划分出4个小壳化石组合带;（3）利用碳同位素资料可以将大海剖面与许多其它剖面相当地层对比;（4）著名的梅树村剖面离大海剖面不远,它们均含有丰富的小壳化石和遗迹化石,两者易于对比。文章进一步认为寒武系的下界放在第I小壳化石组合带（Anabarites trisulcatus-Protohertzina anabarica）的底,相当于大海剖面11层的底。