The Hirnantian δ<Superscript>13</Superscript>C Positive Excursion in the Nabiullino Section (South Urals)

The upper Sandbian, Katian, and Hirnantian complexes of conodonts in the upper Ordovician section of the western slope of the Southern Urals near the village of Nabiullino were studied. The δ¹³C positive excursion with a maximum of 3.3‰ associated with the global Hirnantian isotopic event, HICE, was fixed for the first time. This excursion shows the beginning of the Hirnantian stage in the terrigenous–carbonate section of the upper Ordovician in the Southern Urals. It coincides with the first occurrence of the Hirnantian conodont species of Gamachignathus ensifer and the conodonts of shallow-water biophacies, Aphelognathus-Ozarkodina, reflecting the global glacio-eustatic event.     

Upper carboniferous conodont zones of Russia and their global correlation

The last decade has been marked by significant progress in the study of the stratigraphic ranges of the conodonts characteristic of the Kasimovian and Gzhelian stages in shallow-water sediments of the type sections in the Moscow Basin and the deeper facies of the South Urals. This paper discusses the history of studies of the Upper Carboniferous conodont zonation in Russia and abroad, and proposes a refined zonal conodont scale for the Kasimovian and Gzhelian stages, which may be included, as a standard, into the general Carboniferous scale of Russia. In this scale, the Kasimovian and Gzhelian stages correspond respectively to six (subexcelsus, makhlinae, sagittalis, cancellosus, toretzianus, firmus) and five (simulator, vitali, virgilicus, bellus, wabaunsensis) zones. The proposed scale works for the entire East European Platform and the Urals from the Novaya Zemlya Archipelago in the north to the Mugodzhary Mountains in the south. These regions of Russia are occupied by Upper Carboniferous marine facies. At several levels (especially in the Gzhelian Stage), the scale reliably correlates with zones of the Missourian and Virgilian stages in North America and also Dalaun and Mapingian stages in China.     

Lower Famennian conodont-based stratigraphy of the Pripyat Trough

Three conodont assemblages characterizing the standard triangularis, crepida, and rhomboidea zones can be defined in lower Famennian sections of the Pripyat Trough. The defined local conodont units include the Icriodus iowaensis, Palmatolepis wolskae-Palmatolepis circularis, Palmatolepis klapperi-Polygnathus semicostatus, Icriodus divergentus, and Palmatolepis subperlobata helmsi beds. The defined conodont assemblages are correlated with their coeval standard counterparts of the East European Platform. New conodont species and subspecies are described: Palmatolepis klapperi biparapetus, Polygnathus barskovi, Po. chegodaevi, Po. semeni, Po. inaequilateralis, Polynodosus nodocostatus productus, Icriodus divergentus, I. pushkini.     

First results of U–Pb dating of detrital zircons from the Upper Ordovician sandstones of the Bashkir uplift (Southern Urals)

The first results of U–Pb dating of detrital zircons from Upper Ordovician sandstones of the Bashkir uplift in the Southern Urals and U–Pb isotopic ages available for detrital zircons from six stratigraphic levels of the Riphean–Paleozoic section of this region are discussed. It is established that the long (approximately 1.5 Ga) depositional history of sedimentary sequences of the Bashkir uplift includes a peculiar period lasting from the Late Vendian to the Emsian Age of the Early Devonian (0.55–0.41 Ga). This period is characterized by the following features: (1) prevalence of material from eroded Mesoproterozoic and Early Neoproterozoic crystalline complexes among clastics with ages atypical of the Volga–Urals segment of the East European Platform basement; (2) similarity of age spectra obtained for detrital zircons from different rocks of the period: Upper Vendian–Lower Cambrian lithic sandstones and Middle Ordovician substantially quartzose sandstones.     

Zonation of the Siberian Ordovician deposits based on pelagic groups of fauna

We summarize data on the biostratigraphic units of the Siberian Ordovician deposits based on pelagic groups of fauna: graptolites, conodonts, and chitinozoans. It is shown that graptolite and conodont zones and beds have a high potential for correlation. We have determined the precise zonal position of most of the lower boundaries of the Ordovician stages and informal Ordovician substages of the International Stratigraphic Chart in the Lower Paleozoic key sections of the Taimyr Peninsula, Siberian Platform, and Altai-Sayan Folded Area.     

The paleogeodynamic conditions of redeposition of conodont elements in the late devonian-early carboniferous sediments of the Southern Urals

The peculiarities of conodont fauna redeposition of the Upper Devonian-Lower Carboniferous sediments from different structural-facial zones of the Southern Urals (the Zilair megasynclinorium on the western slope of the Southern Urals (paleocontinental sector) and the Magnitogorsk-Bogdanovsk graben in the central part of the Magnitogorsk megasynclinorium on the eastern slope (paleooceanic sector)) have been studied. The regularities of conodont fauna redeposition in the flysch foredeep and riftogenous depression (of graben) formed in the back of the volcanic arc after volcanism termination have been described.     

Early Stages of the Evolution of Uralides as Evidenced from the U–Pb Systematics of Detrital Zircons from Rift Complexes

The U–Pb isotope data and corresponding ages of detrital zircons from rocks of the basal complexes of the Uralides of different segments of the Ural Fold Belt are considered. It was established that complexes of ancient domains of the East European Platform (Volga-Uralia, Sarmatia, Kola, etc.) seem to have been the main provenance areas of the clastic material for the Southern, Middle, and Northern Urals. This means that there were relatively remote and local (igneous formations of the pre-Uralides) provenance areas. Rift rock associations of the Uralides of the Subpolar and Polar Urals were formed mainly through erosion of local provenance areas (predominantly, Late Riphean–Vendian island-arc and orogenic magmatic complexes of the Proto-Uralides–Timanides). Detrital zircons of Riphean age dominate in rocks of the basal complexes of the Uralides. A source for them could have been rock complexes of Svecofennian-Norwegian Orogen and Cadomides of the Scythian-Turan Plate, intraplate magmatic formations, and metamorphic complexes, as well as blocks accreted to the margin of the East European Platform in the Late Precambrian–Cambrian and later detached and displaced during the Ordovician rifting and spreading. In general, the basal complexes of Uralides were formed owing to supply of clastic material from both remote and local sources. Despite the appearance of information of a totally new level (U–Pb isotope ages of detrital zircons, their Lu–Hf systematics, and the distribution features of rare earth and trace elements), the contribution of these sources to the formation of the Late Cambrian–Early Ordovician clastic strata is hardly possible at present to evaluate.     

Conditions of formation of igneous rocks in plume magmatism at the example of the western slope of the Southern Urals

This work presents new data on the conditions of formation of igneous rocks on the western slope of the Southern Urals and the adjacent part of the East European Platform. Based on the calculated P–T melting parameters of the mantle substrate, it is shown that plume magmatism leads to the formation of similar rocks (picrites and picrite-dolerites), while the genesis of them is quite different. The first type of rocks is a product of crystallization of the undifferentiated mantle-derived melt in the upper horizons of the crust; the rocks of the second type are formed as a result of magma differentiation in large intracrustal magma chambers.     

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.     

华北板块奥陶纪牙形石生物地层研究回顾及在西北缘区新进展

牙形石在以碳酸盐岩为主的华北奥陶系划分对比中占有举足轻重的地位。针对华北奥陶纪牙形石的研究已持续近半个世纪,总体上可以分为两个阶段:第一阶段自20世纪70年代到21世纪初,第二阶段为最近10年(2010—2020)。第一阶段以建立牙形石生物地层序列为目标,主要为解决石油勘探过程中地层时代的确定和地层对比的需求;第二阶段的研究以修订化石带为主,目的是与国际地层研究接轨。近年来在华北板块西北缘的工作显示,该区奥陶纪牙形石在纵向上具有显著的生态变化,可分为达瑞威尔期中期、达瑞威尔期晚期—桑比期中期、桑比期晚期—凯迪期中期3个时段。第一时段以介于北美中大陆区和北大西洋区之间的热带台地边缘型牙形石为特征;第二时段以北大西洋型为主混有少量亚澳型牙形石为特征;第三时段以亚澳型和北美中大陆型牙形石混生为特征。在华北西北缘尽可能使用广布性标准牙形石属种进行化石带厘定,共识别牙形石带12个,自下而上分别是达瑞威尔期Histiodella cf. holodentata间隔带、Histiodella kristinae谱系带、Histiodella bellburnensis延限带、Dzikodus tablepointensis间隔带、Eoplacognathus suecicus间隔带、Pygodus serra间隔带和Pygodus anserinus(早期型)间隔亚带,桑比期Pygodus anserinus(晚期型)间隔亚带和Belodina compressa间隔带,凯迪期Belodina confluens间隔带、Yaoxianognathus neimengguensis间隔带和Yaoxianognathus yaoxianensis间隔带。由于部分化石带与国际同名带的对比还存在一些矛盾,尚需今后进一步解决。     

华南下/中奥陶统界线附近笔石相的分异与全球下/中奥陶统界线生物标志的选择

通过对宜昌黄花场(扬子地台中部)大湾组剖面和重庆城口(扬子地台北部)的湄潭组剖面笔石动物群特征的分析,结合江西崇义地区(盆地相)、江南过渡带笔石动物群的研究成果,讨论了华南下／中奥陶统界线附近笔石相分异的现象,并探讨了下／中奥陶统界线附近笔石动物和牙形石的相互关系。认为宜昌黄花场剖面完全具备建立全球下／中奥陶统界线层型剖面和点(GSSP)的条件,牙形石B.triangularis的首次出现(FAD)是良好的界线生物标志。     

Resistivity pattern of crust and upper mantle in Southern Urals

A resistivity model of the southern Urals to depths of 120 km was obtained by numerical simulation of natural- and controlled-source EM soundings at 160 kHz to 4⋅10⁻⁴ Hz. The structure of crust and upper mantle was imaged along a transect running ∼800 km across the East European Platform, the Ural foredeep, and the Ural mountains. The new data on geology and tectonics of the southern Urals enlarge the knowledge gained through URSEIS-95 reflection profiling along one of best representative cross-orogen profiles. We discovered a large conductor traceable to depths at least 100–120 km at the junction between the East European Platform and the Ural foredeep. It indicates that the Ural foredeep originated in a weak tectonic zone at the platform edge. The Ural orogen is imaged as a nearly bivergent structure to depths of 70–80 km producing a mosaic pattern of conductors rooted deep beneath the Magnitogorsk greenstone province and the granitic belt of the central East Ural uplift where it is 150 km wide at a depth of ∼120 km. We interpret the discovered deep roots in the context of the geological history of the Urals.     

新疆塔中南坡奥陶系的地层缺失和沉积相变化

按照奥陶系内部6个组沉积的时间片段拟定塔中南坡不同区块存在不同程度的缺失。部分关键层段的牙形石和几丁虫组合特征证明一间房组和恰尔巴克组在塔中部分井区是存在的,但恰尔巴克组的分布范围最狭窄。总体上,塔中南坡隆起区地层缺失较多,古城墟隆起基本完整。据缺失状况和岩相展布,显示塔中南坡的沉积单元具有由东往西迁移的特征,且各时段迁移的距离与速度存在较大差异。     

The East European Platform in the late Ediacaran: new paleomagnetic and geochronological data

The paleogeography of the Earth, including the East European Platform, is very inaccurately defined for the interval 500–700 Ma. The quantity and quality of Late Precambrian–Cambrian paleomagnetic data on this platform are absolutely insufficient for reliable paleogeographical or paleotectonic reconstructions. Since there are almost no unstudied objects in the platform that could be used for paleomagnetic studies, it seems reasonable to consider the deformed platform margins. Of particular interest is the Bashkir anticlinorium (South Urals) with numerous Ediacaran sedimentary sections, some of which contain tuff beds suitable for isotope dating. We present paleomagnetic and geochronological data on the Upper Ediacaran Zigan Formation, sampled in the western part of the western limb of the Bashkir anticlinorium. The East European Platform must have been at near-equatorial latitudes at ～550 Ma.     

牯牛潭组与庙坡组的界线

<正> 牯牛潭组和庙坡组是张文堂(1962)命名建立的,标准剖面位于湖北宜昌分乡镇西侧的牯牛潭。牯牛潭组以灰岩与瘤状灰岩为主,厚约20m;庙坡组为页岩夹灰岩,厚约2m,页岩的出现为庙坡组的开始。长期以来这一观点被广大地质工作者所接受。70年代初南京地质古生物研究所西南队在湖北宜昌黄花场重测奥陶系剖面时,在牯牛潭组顶部约0.5m厚的地层中发现了三叶虫Birmanites hupeiensis Yi,Lonchodomas brevicis Lu,     

The Carbonate Massif of Voskresenka Mount in the Southern Pre-Urals: Age and Development of the Submerged Carbonate Platform

In the conjunction zone of the East European Platform and the Uralian foredeep, involved in structures of the Southern Urals (Bashkiria), sediments deposited at the shelf zone edge in the Late Carboniferous–Early Permian crop out. The Upper Carboniferous bioherm and Lower Permian deep marine–shelf boundary limestones, composing Voskresenka Mount near Tabynsk township, were studied. Results of the complex analysis of lithofacies, paleontological, structural, and also geological and geophysical data show that the Voskresenka carbonate massif, previously attributed to a single reef structure, represents the SW-dipping tectonic horst block, composed of Upper Carboniferous shelf–bioherm limestones, which is uplifted in a near break zone. As a result of tectonic processes, the edge of the late Carboniferous carbonate platform, overlain by Asselian deep-water sediments, was exhumed. The sedimentary succession shows that the paleogeographic setting at the margin of the East European Craton changed at the Carboniferous–Permian boundary during the formation of the Ural collisional orogen.     

Problems correlating the late Brigantian–Arnsbergian Western European substages within northern England

A detailed study of foraminiferal assemblages recorded in limestones from northern England in the Stainmore Trough and Alston Block permits their assignment to different European substages than in previous studies. Comparisons with foraminiferal assemblages, mostly from Russia, allow the biozonations to be correlated with the Viséan, Serpukhovian and Bashkirian international stages, as well as with the Russian (and Ukrainian) substages for the Serpukhovian (Tarussian, Steshevian, Protvian and Zapaltyubian). The Scar Limestone and Five Yard Limestone Members are assigned to the Tarussian and, thus, represent the lowermost part of the formal Serpukhovian Stage. This new correlation coincides closely with the first occurrence of the conodont Lochriea ziegleri from levels equivalent to the Single Post Limestone that could potentially form the revised base for the Serpukhovian. The Three Yard Limestone Member is correlated with the base of the Steshevian substage which also includes the Four Fathom Limestone Member, Great Limestone Member and Little Limestone. The base of the Protvian is considered to lie within the Crag Limestone, whereas the Rookhope Shell Band contains foraminiferal assemblages more typical of the Zapaltyubian in the Ukraine and Chernyshevkian in the Urals. Assemblages of the Upper Fell Top Limestone and Grindstone/Botany Limestones contain foraminiferal species that have been used for the recognition of the Bashkirian elsewhere. There is no other fossil group which allows the calibration of those foraminiferal assemblages, because ammonoids are virtually absent in the shallow‐water cyclothemic successions and conodonts have not been studied in detail in this region. The Mid‐Carboniferous boundary and the Voznessenian substage might be reasonably located below the Upper Fell Top Limestone. Copyright © 2015 John Wiley & Sons, Ltd.     

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     

华南上扬子区早-中奥陶世疑源类古环境意义

对上扬子区 7个剖面早—中奥陶世疑源类研究表明 ,这些疑源类组合在分异度及属种组成上呈现有规律的变化 ,这种变化是上扬子区古环境变化的反映。在上扬子区西部 ,近岸碎屑岩相沉积的滇东红石崖组所产疑源类组合分异度低 ,为个体较小、壳饰较简单的分子 ;上扬子区中部 ,以黔北湄潭组为代表的浅海相碎屑岩和灰岩沉积中 ,疑源类分异度较高 ,并出现许多个体较大、壳饰较复杂的分子 ;而在上扬子区东部鄂西宜昌大湾组陆棚相灰岩与泥岩中 ,疑源类分异度继续增高 ,其中个体大、具粗大、长而复杂突起的分子占优势。