Local Bryozoan biostratigraphic zones of the Eifelian stage (Middle Devonian) of the western Altai-Sayan Folded Area

Bryozoan assemblages from the lower part of the Middle Devonian of the western Altai-Sayan Folded Area are studied because of the recent discovery of Eifelian ammonoids (Cabrieroceras crispiforme Zone) in the Safonovo Formation, which had been previously dated as Givetian. The bryozoan collection (21 species) was sampled from six sections of the Mamontovo Regional Substage (“Horizon”) of the Eifelian Stage, seven sections of the Safonovo formation of Salair, and one section of the upper part of the Melnichnaya Formation of Rudnyi Altai. Two groups of bryozoans with different species composition are recognized, one of which occurs in the Malaya Salairka Beds of the Mamontovo Horizon, whereas the other occurs in the Safonovo Formation immediately below the Cabrieroceras crispiforme Zone. Two local biostratigraphic zones are recognized on the basis of these groups (Eridotrypella distributa and Leptotrypa spinosa zones), characterizing the lower and upper parts of the Eifelian Stage of the western Altai-Sayan Folded Area.     

Magnetic stratigraphy of the Permian-Triassic traps in the Kotui River valley (Siberian Platform): New paleomagnetic data

The Permian-Triassic effusive traps in the Kotui River valley (Siberian Platform) were studied in detail by a paleomagnetic method, resulting in a summarized magnetic stratigraphic section of the studied sequence. The presence of the reversed polarity zone corresponding to the Khardakh Formation was argued for the section basement. Inside the Kogotok Group, the boundary between the direct and reversed polarity zones occurs in the lower part of the Onkuchak Formation and mismatches the boundary between the formations of the Kogotok Group, as was accepted before. These results contradict the presence of the transition record between the direct and reversed polarity zones in basalts of the lower part of the Onkuhcak Formation. The strong transitional interval between the Ivakinsk Formation and the upper parts of the Nadezhda Formation of the Norilsk section has no analogs in the Kotui section. This means the absence of any significant volcanic activity in the Maimecha-Kotui province during the intense eruptions in the Norilsk region resulting in origination of the greater part of the lower formations of the trap sequence. These data and possible correlations of the traps of the Kotui River valley and Norilsk region indicate that the Norilsk and Maimecha-Kotui sections were temporally overlapped.     

西秦岭地区晚二叠世—早三叠世沉积相分析和沉积古环境再造

青海省同仁地区处于祁连和秦岭造山带的接合部，构造演化历史悠久。本次工作在该地区隆务河一带发现较好的二叠—三叠系剖面。将该剖面从下而上划分为上二叠统石关组、下三叠统果木沟组和江里沟组，其中江里沟组又进一步划分为下部的浊积岩段和上部的风暴岩段，初步确定了二叠—三叠纪的界线。沉积序列、沉积相和沉积物表明上二叠统石关组和下三叠统果木沟组为一套陆源碎屑浊积岩，下三叠统江里沟组下部为一套不纯的内碎屑浊积岩，而下三叠统江里沟组上部为风暴岩沉积。根据沉积相和火山岩夹层的地球化学特征认为该地区上二叠统石关组和下三叠统果木沟组处于半深海的活动大陆边缘，下三叠统江里沟组早期的浊积岩段处于较稳定的半深海大陆边缘。根据沉积相和遗迹化石，恢复了晚二叠世—早三叠世的海平面变化特征。     

吕梁山地区新近纪晚期地层研究进展

通过对吕梁山西部保德和柳林两个典型剖面的研究,认为山西柳林卫家洼保德组剖面结构与保德剖面相同,完全可以对比。保德组下部的砂砾石确为水成堆积无疑,但是上部的棕红色黏土与棕黄色的钙质结核层越来越被广大学者认为是风尘堆积,中部则为下部水成堆积物与上部红黏土与钙质结核的过渡地段。《中国地层指南及中国地层指南说明书》规定:组的含义在于岩性、岩相和变质程度的一致性,除去变质程度不说,保德组下部水成堆积物和上部风尘堆积根本不是同一相环境所能包含的岩石组合,因此不能用一个组来定义,应予解体。保德组下部的水成堆积物划为芦子沟组,相当于初始定义的"芦子沟系"或"芦子沟砾岩";保德组上部风尘堆积仍称之为保德组,相当于初始定义的保德红土;在这种划分下芦子沟组为不整合于前新生代基岩之上,整合伏于红黏土之下的山前冲积扇相堆积。保德组为整合于芦子沟组之上静乐组之下的所有风尘堆积。     

Sizing up the sub-Tommotian unconformity in Siberia

Sedimentary rocks in the western Anabar region, northwestern Siberia, preserve an exceptional record of evolution and biogeochemical events near the Proterozoic-Cambrian boundary. Carbon isotopic data on petrographically and geochemically screened samples collected at 1 to 2 m intervals support correlation of the lower Anabar succession (Staraya Reckha and lower Manykai Formations) with sub-Tommotian carbonates of the Ust'-Yu-doma Formation in southeastern Siberia. In contrast, the upper Manykai and most of the overlying Medvezhya Formation appear to preserve a sedimentary and paleontological record of an evolutionary important time interval represented in southeastern Siberia only by the sub-Tommotian unconformity. Correlation of the Anabar section with other northern Siberian successions that contain well-dated volcanic rocks permits the estimate that the sub-Tommotian unconformity in southeastern Siberia spans approximately 3 to 6 m.y. Diverse small shelly fossils (but not archaeocyathans) previously thought to mark the base of the Tommotian Stage evolved sequentially throughout this earlier interval.     

On age of Nazimovskaya and Khasan formations in the Paleogene succession of southwestern Primor’e

Materials of previous studies and new original geological and paleobotanic data are used to substantiate synchronism (late Eocene) of the Khasan and Nazimovskaya formations, the key stratigraphic units of the Paleogene in Primor’e. Coal-bearing sediments of the units rest upon early-middle Eocene volcanics (Kraskino rhyolite tuffs, Zaisanovka basaltic andesites) being overlain by the lower Fatash Subformation of the lower Oligocene with flora of the Kraskino type. The Ust’-Davydovskaya Formation of the Rechnoi Peninsula (outskirts of Vladivostok) is the most probable analogue of the Khasan (=Nazimovskaya) Formation.     

On the Yangtzeconus Priscus-Archaeospira Ornata Assemblage (Mollusca) of the Earliest Cambrian of China

Yangtzeconus priscus-Archaeospira ornata, an important earliest Cambrian benthonic Assemblage of the Yangtze micromolluscan fauna, occurs mainly in the Lower Cambrian Zhongyicun and Dahai Members of the Yuhucun Formation in E Yunnan, the Tianzhushan Member （=Huangshandong Member） of the Dengying Formation in W Hubei and the Maidiping Member of the Hungchunping Formation in C Sichuan, China. About 90% of the genera of this Assemblage are unknown from the Nemakit-Daldynian and Tommotian molluscan Assemblages of the Siberian Platform, Russia. About 90% of the Siberian molluscan genera do not occur in the Zhongyicun and Dahai Members in the Meishucun section and in the corresponding beds of the Yangtze Platform, because the Tommotian molluscan Assemblage is characterizedly abundant archaeocyathids. It is clearly indicated that the Yangtze and Siberian molluscan Assemblages represent different bio- and lithofacies and ages. The age of the pre-trilobitic Yangtzeconus priscus-Archaeospira ornata Assemblage is older than that of the Nemakit-Daldynian and Tommotian molluscan Assemblages and referable to the Earliest Cambrian. Two new genera Mcnamaraconus and Zhangwentangoconus are herein proposed.     

Fusulinid biostratigraphy of the Lower Permian Zweikofel Formation (Rattendorf Group; Carnic Alps,Austria) and Lower Permian Tethyan chronostratigraphy

The Zweikofel Formation of the Rattendorf Group in the Carnic Alps (Austria) is 95–102 m thick and consists of a cyclic succession of thin‐ to thick‐bedded fossiliferous limestone and intercalated thin intervals of siliciclastic sediment. The siliciclastic intervals were deposited in a shallow marine nearshore environment. The variety of carbonate facies indicates deposition in a shallow neritic, normal‐saline, low‐ to high‐energy environment. The Zweikofel Formation is characterized by a paracyclic vertical arrangement of facies and represents sedimentary sequences that are not well understood elsewhere in the Tethys. Fusulinids and conodonts from the upper Grenzland and Zweikofel formations in the Carnic Alps clearly suggest that what has been called ‘Sakmarian’ in the Tethys includes both the Sakmarian and Artinskian stages of the Global Time scale. Fusulinids from the lower part of the Zweikofel Formation at Zweikofel closely resemble those of the Grenzland Formation and approximately correlate with the upper part of the Sakmarian and lower part of the Artinskian of the Global Time scale. The upper part of the Zweikofel Formation correlates approximately with the lower‐middle (?) parts of the Artinskian Stage of the Global Time scale. A new regional Hermagorian Stage of the Tethyan scale is proposed between the Asselian and Yakhtashian. The lower boundary of the Hermagorian Stage is proposed to be located at the base of bed 81 in the 1015 section of Darvaz (Tadzhikistan). The boundary between the Hermagorian and Yakhtashian stages is placed at the base of bed 73 in the Zweikofel section at Zweikofel, Carnic Alps. In the Darvaz region, Tadzhikistan, the type area for the Yakhtashian Stage, this boundary has never been precisely defined. The entire fusulinid assemblage of the upper part of the Grenzland and Zweikofel formations reported herein includes 62 species of 18 genera, of which one subgenus and 12 species and subspecies are new. Copyright © 2012 John Wiley & Sons, Ltd.     

New Data on the Age of the Yukiang (Yujiang) Formation at Liujing, Guangxi, South China

The age of the Yukiang (Yujiang) Formation has been shrouded in controversy for more than 75 years. New investigation at the Liujing section, Hengxian County, Guangxi, has revealed a conodont sequence assignable to two Early Devonian conodont zonations: the Eognathodus kindlei?–Polygnathus pireneae Zone and the Polygnathus nothoperbonus Zone from oldest to youngest. The Gaoling and Mahuangling members of the Nahkaoling (Nagaoling) Formation and the overlying Xiayiling Member and lower part of the Shizhou Member of the Yukiang Formation are proven to belong to the Pragian Eognathodus kindlei?–Polygnathus pireneae Zone. The co-occurrence of Polygnathus pireneae and Pol. sokolovi in the lower part of the Shizhou Member demonstrates that this interval can be approximately correlated with the uppermost part of the Polygnathus pireneae Zone. However, precise level identification of the Pragian–Emsian Boundary (PEB) in the Liujing section remains dfficult due to the scarcity of suitable limestone samples for conodont analysis from the middle and upper parts of the Shizhou Member. The Daliancun and Liujing members of the Yukiang Formation and the lower part of the overlying Moding Formation are assigned to the Polygnathus nothoperbonus Zone with the nominal species of this biozone ranging from the bottom of the Daliancun Member to the lower part of the Moding Formation.     

内蒙古达茂旗巴特敖包地区的西别河剖面与西别河组

内蒙古达茂旗巴特敖包地区的西别河剖面是西别河组的建组剖面,时代争议较大。西别河剖面的牙形刺研究表明：西别河剖面的下、中部应归入上志留亚系(Ludlow to Pridoli),发现了可与Ludlow统标准牙形刺带Ozarkodina crispa对比的牙形刺Ozarkodina uncrispa。剖面的上部为下泥盆统阿鲁共组,时代为Lochkovian 阶,发现了下泥盆统Lochkovian阶特有的牙形刺属Ancyrodelloides, Lanea。西别河剖面不宜作西别河组的标准剖面,包尔汉图剖面可作为西别河组的标准剖面。     

Taxonomic composition and biostratigraphic value of the Early Riphean organic-walled microfossil association from the Ust’-Il’ya Formation of the Anabar Uplift,Northern Siberia

It is demonstrated on the basis of the first monographic study of multiple and taxonomically variable organic-walled microfossils from the Ust’-Il’ya Formation of the Anabar Uplift that both prokaryotic and eukaryotic forms are present in the composition of this microbiota. They are divided into four formal groups on the basis of the specifics of the morphological indicators of the identified taxa. The review of the data on the isotopic age of hosting deposits showed that the Ust’-Il’ya Formation is of the Early Riphean in age which are currently evaluated as 1750 ± 10–1400 Ma. Relatively large and morphologically complex eukaryotic forms present in the Ust’-Il’ya Formation served in due time as the basis for an erroneous conclusion on the Late Riphean age of the specified formation and the overlying Lower Kotuikan Subformation of the Anabar Uplift. The paper provides a global comparative analysis of the Early Riphean microbiotas, demonstrates the position of the Ust’-Il’ya and Kotuikan microbiotas amidst the microbiotas of the same age, and shows that the relatively large acanthomorphic acritarchs Tappania, Valeria, Dictiosphaera, Satka, and Shuiyousphaeridium appeared in the geological history already during the Early Riphean Erathem. Moreover, the paper discusses the recently published data on the distribution of aerobic and anaerobic conditions in the Early Riphean paleobasins and provides the conclusion on the impact of the lateral change of these conditions on the taxonomic composition of the microbiota.     

扬子区寒武系底部含磷岩系沉积特征对比与成矿规律

扬子区寒武系底部含磷岩系主要蕴藏于梅树村期地层中,因沉积相类型多样,含磷岩系复杂,沉积厚度变化大,含大量磷矿资源而具有重要的研究价值.对研究区13条含磷岩系剖面进行野外勘查和大区域横纵向综合对比研究,结果表明:含磷岩系沉积层序自下而上显示颗粒由粗变细,层理类型由交错层理、波状层理及粒序状层理转为平行层理,生物屑减少至消...     

浙江临安板桥奥陶系胡乐组笔石新材料及其意义

报道在浙江临安板桥奥陶系剖面的胡乐组中发现的较丰富的笔石动物群,包括Pterograptus elegans,Expansograptus sp.1,Tylograptus sp.,Cryptograptus?sp.,Archicli macograptus angulatus,A.caelatus,Procli-macograptus angustatus等主要属种,应属达瑞威尔阶Pterograptus elegans笔石带。这一发现表明,临安板桥一带的胡乐组时代跨度非常局限,底界比浙赣交界"三山地区"的胡乐组之底高2个笔石带,顶界对比则低2个笔石带。其下伏牯牛潭组的顶界与宜昌三峡地区相比,也低了2个笔石带,具明显的穿时现象。     

Distinguishing eustatic and epeirogenic controls on Lower–Middle Cambrian boundary successions in West Gondwana (Morocco and Iberia)

Major eustatic fall has been invoked to explain Lower–Middle Cambrian boundary sandstones and faunal replacements on a number of Cambrian palaeocontinents. This proposal has been tested on the Moroccan and Spanish margins of West Gondwana and found to be inadequate to explain stratigraphical developments. In these regions, sandstone intervals long presumed to be regressive and late Early Cambrian in age are now shown to be early Middle Cambrian, and composed of a lower regressive and an overlying transgressive sandstone separated by a regional unconformity. Only the lower tidalites (i.e. Tazlaft Formation in Morocco and lower Daroca sandstones in Spain) record the Hawke Bay eustatic regression in West Gondwana. The Tazlaft is overlain by a newly recognized, unconformably overlying sandstone (Talelt Formation) that onlapped southern Morocco with reactivation of a pull‐apart or transcurrent regime. Up to 150 m of erosion on uplifted blocks in the High Atlas range and foundering of the Souss Basin to the south preceded onlap and deposition of the volcanic‐rich Tatelt, the correlative and depositional analogue of the upper Daroca and lower Valdemides Formations in northern Spain. With folding and erosion, a type 1 depositional sequence boundary also caps the Tatelt at its contact with an overlying, lower Middle Cambrian mudstone‐dominated succession. This unconformity probably occurs in Spain within the Valdemiedes Formation and corresponds to a faunal discontinuity called the ‘Valdemiedes geoevent’. The Iberian ‘Daroca regression’ and Moroccan ‘Asrir regression’ are misnomers, as the sandstones on which they are based are composite units with a lower regressive interval that records eustatic fall and an upper transgressive unit that records epeirogenically driven onlap.     

C and Sr isotope chemostratigraphy of Vendian-Lower Cambrian carbonate sequences in the central Siberian Platform

We propose a detailed δ¹³C curve for the Vendian and Lower Cambrian (Tommotian) strata of the central Siberian Platform. Two positive carbon isotope excursions identified near the base of the Yuryakh Formation (up to 5.5‰) and in the lower Bilir Formation (up to 5‰) are assigned to the lowermost and middle Tommotian, respectively. This correlation is supported by paleontological data, specific ⁸⁷Sr/⁸⁶Sr values (0.70845-0.70856), and similar C isotope record in coeval Early Cambrian basins. The documented minor vertical oscillations (a few meters) of these isotope excursions relative to the formation boundaries in remote boreholes is presumably caused by the spatiotemporal migration of facies. A high-amplitude negative δ¹³C excursion (-8 to -11‰) in the upper Nepa Regional Stage putatively corresponds to the global Shuram-Wonoka negative carbon isotope excursion (Middle Ediacaran). Carbonates of the lower Nepa Regional Stage (Besyuryakh Formation) demonstrate positive δ¹³C values (up to 5‰) and minimum ⁸⁷Sr/⁸⁶Sr ratios of 0.70796-0.70832. The C and Sr isotope record of the Nepa Regional Stage provides its robust correlation with the Dal’nyaya Taiga and Zhuya Groups of the Patom Foredeep. Micropaleontological data herein reported and glacial diamictites documented at the base of the Vendian sedimentary cover both in the central Patom Foredeep and on its periphery suggest a full stratigraphic volume of the Ediacaran System in the most stratigraphically complete sections of the central Siberian Platform.     

西秦岭北带泥盆系舒家坝组深海陆源碎屑沉积序列的研究

西秦岭北带泥盆系舒家坝组属中晚泥盆世,地层总厚超过２０００ｍ。除最上部碳酸盐岩段外,主要是细、粉砂岩与页（泥）岩不等厚五层组成的沉积序列。本文从以下三个方面论证该序列形成于半深海－深海环境:１）时空上主要是由分布稳定的细粒浊积岩组成;２）等深积岩与浊积岩相伴而生;３）在浊积岩系和深海泥页岩中发现了高分异度、高丰度的遗迹化石共４１个属,其中占遗迹总属的８０%为深水型分子。此外,从岩相、垂直序列和古水流三方面的特征论证了舒家坝组属非扇沉积模式。     

U–Th age of the Kazantsevo (MIS 5) Horizon of the Upper Neopleistocene Ust Oda reference section,Baikal Region

For the first time, the organic sediments of the Kazantsevo Horizon (Baikal Region) were characterized geochronometrically. The ²³⁰Th/U age of the buried gyttias from the Upper Neopleistocene Ust Oda stratotypical section on the Kitoi River was determined using a new version of isochronous approximation. The assemblage of all the ²³⁰Th/U age data, which were obtained taking into account the errors in the entire range from 136 to 86 kyr, indicates that most likely gyttia age is 115–104 kyr (MIS 5d). Thus, the paleontological conclusions on the Kazantsevo age of the Ust Oda Formation with buried gyttias are confirmed. Our geochronometric data supplement and make more reliable the age model of the formation of sedimentary rocks of the Ust Oda section.     

A ‘snapshot’ of the evolution of the Uruguay River (Del Plata Basin): the Salto depositional sequence (Pleistocene,Uruguay, South America)

This paper provides sedimentological details of the Salto depositional sequence of western Uruguay, which includes the Salto and the Bellaco Formations. These units are interpreted as evidence, in the Uruguayan landscape, of a Pleistocene forebear of the Uruguay River. The Salto depositional sequence, encompasses two depositional cycles: (a) the lower cycle, represented only by the Salto Formation, with conglomeratic sandstones and sandstones intercalated with pelites and fine sandstones; and (b) the upper cycle, represented by the Salto Formation and the Bellaco Formation, characterized by conglomerates and conglomeratic sandstones with horizontal stratification, discontinuous silicified sandy levels and gypsum–clay bodies. The Salto sequence is characterized by braided river deposits, genetically associated with lacustrine or palustrine and possible aeolian sediments. Cyclic alternations of channelized tractive currents and interchannel contexts are indicated. A possible Pleistocene age for the Salto Formation is discussed, in the light of new and preliminary information (thermoluminescence ages) from the lower cycle. There are several lines of evidence indicating semi-arid conditions during the ‘Salto event’. Comments on regional correlation are provided, as well as the effects of neotectonic processes.     

漠河盆地上侏罗统层序地层格架

漠河盆地出露了较完整的上侏罗统 ,6条绣峰组、二十二站组、额木尔河组及开库康组露头剖面层序地层分析和不同剖面间层序对比结果表明 ,漠河盆地从绣峰组到开库康组在垂向上发育了 36个三级层序 ,构成绣峰、二十二站、额木尔河和开库康 4个超层序。门都里东山绣峰组剖面和二十二站组剖面出露了较完整的绣峰和二十二站超层序 ,瓦拉干—二十二站绣峰组剖面出露的是绣峰超层序中上部和二十二站超层序底部地层 ,二十二站北山二十二站组剖面出露的是二十二站超层序中上部和额木尔河超层序下部地层 ,小丘古拉河额木尔河组剖面出露的是额木尔河超层序中上部和开库康超层序下部地层 ,开库康乡开库康组剖面出露的是开库康超层序的上部地层。