Problems of Oxfordian and Kimmeridgian stratigraphy in northern Central Siberia (Nordvik Peninsula section)     

B.L. Nikitenko  V.G. Knyazev  N.K. Lebedeva  E.B. Peshchevitskaya  R.V. Kutygin 《Russian Geology and Geophysics》2011,52(9):963-978

The Oxfordian–Lower Hauterivian section of the Nordvik Peninsula (northern Central Siberia) is a reference for developing zonal scales for various fossil groups and improving the Boreal zonal standard. In the middle 1950s–late 1980s, it was studied extensively by geologists, stratigraphers, lithologists, and experts on various fossil groups. These studies yielded rich fossil and microfossil collections and a set of parallel zonal scales for various faunal groups. Recently, a new detailed ammonite zonation of the Oxfordian and Kimmeridgian units of this section has been proposed. These results contradict the previous biostratigraphic data on ammonites, foraminifers, and palynomorphs. In the present paper, all the biostratigraphic data on the Oxfordian and Kimmeridgian units of the Nordvik Peninsula (Cape Urdyuk-Khaya) and northern Central Siberia undergo a comprehensive analysis and comparison with those on the Boreal Realm. The ammonite-constrained stratigraphic position of the lower Upper Jurassic in the Cape Urdyuk-Khaya section is interpreted as Upper Oxfordian or Middle Oxfordian. In our view, this difference in the understanding is due to the misidentification of some Oxfordian ammonite forms. The zones based on other fossil groups (foraminifers, dinocysts) which were distinguished in the Upper Oxfordian and Kimmeridgian sections of the Nordvik Peninsula are well traceable circumarctically. Their stratigraphic position in various regions of the Northern Hemisphere is constrained by ammonites and bivalves. However, if we use the last alternative ammonite zonation of this section part, hardly explicable contradictions will appear in interregional foraminiferal and dinocyst correlations.  相似文献   

The North Taymyr ice-marginal zone, Arctic Siberia—a preliminary overview and dating     

Helena Alexanderson  Christian Hjort  Per Mller  Oleg Antonov  Maksim Pavlov 《Global and Planetary Change》2001,31(1-4)

The North Taymyr ice-marginal zone (NTZ) is a complex of glacial, glaciofluvial and glaciolacustrine deposits, laid down on the northwestern Taymyr Peninsula in northernmost Siberia, along the front of ice sheets primarily originating on the Kara Sea shelf. It was originally recognised from satellite radar images by Russian scientists; however, before the present study, it had not been investigated in any detail. The ice sheets have mainly inundated Taymyr from the northwest, and the NTZ can be followed for 700–750 km between 75°N and 77°N, mostly 80–100 km inland from the present Kara Sea coast.The ice-marginal zone is best developed in its central parts, ca. 100 km on each side of the Lower Taymyr River, and has there been studied by us in four areas. In two of these, the ice sheet ended on land, whereas in the two others, it mainly terminated into ice-dammed lakes. The base of the NTZ is a series of up to 100-m-high and 2-km-wide ridges, usually consisting of redeposited marine silts. These ridges are still to a large extent ice-cored; however, the present active layer rarely penetrates to the ice surface. Upon these main ridges, smaller ridges of till and glaciofluvial material are superimposed. Related to these are deltas corresponding to two generations of ice-dammed lakes, with shore levels at 120–140 m and ca. 80 m a.s.l. These glacial lakes drained southwards, opposite to the present-day pattern, via the Taymyr River valley into the Taymyr Lake basin and, from there, most probably westwards to the southern Kara Sea shelf.The basal parts of the NTZ have not been dated; however, OSL dates of glaciolacustrine deltas indicate an Early–Middle Weichselian age for at least the superimposed ridges. The youngest parts of the NTZ are derived from a thin ice sheet (less than 300 m thick near the present coast) inundating the lowlands adjacent to the lower reaches of the Taymyr River. The glacial ice from this youngest advance is buried under only ca. 0.5 m of melt-out till and is exposed by hundreds of shallow slides. This final glaciation is predated by glacially redeposited marine shells aged ca. 20,000 BP (¹⁴C) and postdated by terrestrial plant material from ca. 11,775 and 9500 BP (¹⁴C)–giving it a last global glacial maximum (LGM; Late Weichselian) age.  相似文献   

Flood zone biogeochemistry of the Ob River middle course     

《Applied Geochemistry》2015

The flood zone of the Ob River, the largest (in watershed area) river of the Arctic Ocean basin, is tens of km wide and, after the Amazon's Varzea, is the world's second largest flooding territory. To better understand the biogeochemistry of the Ob River and adjacent surface waters, we studied, in May and July 2014, the dissolved and colloidal organic carbon and trace metals in small rivers, lakes, and flooded water bodies connected and disconnected with the mainstream as well as the Ob River itself. All major and trace elements were distributed among two major categories depending on their pattern of dependence on the dissolved organic carbon (DOC) concentration. Dissolved inorganic carbon (DIC), Na, Mg, Ca, sulfate, Sr, Mo, Sb and U exhibited a general decrease in concentration with the increase of the [DOC]. The lowest concentration of these elements was observed in DOC-rich humic, acidic (4.9 ≤ pH ≤ 6.1) upland lakes fed by surrounding bogs. These elements marked the influence of underground feeding in July during summer baseflow, which was most visible in flood lakes in the Ob riparian zone and the Ob River itself. In May, the flood lakes were statistically similar to the Ob River. The elevated concentration of DOC (up to 60 mg/L) in the upland lakes was not correlated with groundwater-related elements, suggesting a lack of significant groundwater feeding in these lakes. In contrast, insoluble, usually low mobile elements (Al, Fe, other trivalent hydrolysates, Ti, Zr, Hf) and some metals (Cr, Zn, Ni, Pb) demonstrated a steady increase in concentration with increasing DOC, with the lowest values observed in the Ob River and the highest values observed in small tributaries and organic-rich upland lakes in July. It follows that these elements are limited by their main carriers – organic and organo-ferric colloids, rather than by the availability of the source, peat and mineral soil or plant litter. While for the majority of non-colloidal, groundwater-fed elements with high mobility (DIC, Na, Mg, Ca, K, Sr…) the small tributaries can be used as representatives of the Ob main stream, this is not the case for low mobility “insoluble” elements, such as Fe, Al, trivalent and tetravalent hydrolysates, and metal micronutrients (Cu, Zn, and Mn). The low soluble elements and divalent metals exhibited a much lower concentration in the river mainstream compared to that in the flood lakes, upland lakes and small rivers. This difference is significantly more pronounced in the baseflow in July compared to the spring flood in May. Presumably, autochthonous processes, such as the photo-oxidation and bio-oxidation of organo-ferric colloids and phytoplankton uptake are capable decreasing the concentration of these elements in the river mainstream.  相似文献   

Southern East Siberia Pliocene–Quaternary faults: Database, analysis and inference     

Oksana V. Lunina  ;Riccardo Caputo  ;Anton A. Gladkov  ;Andrey S. Gladkovt 《地学前缘(英文版)》2014,5(4):605-619

This paper presents the first release of an Informational System（IS）devoted to the systematic collection of all available data relating to Pliocene-Quaternary faults in southern East Siberia,their critical analysis and their seismotectonic parameterization.The final goal of this project is to form a new base for improving the assessment of seismic hazard and other natural processes associated with crustal deformation.The presented IS has been exploited to create a relational database of active and conditionally active faults in southern East Siberia（between 100°-114° E and 50°-57° N）whose central sector is characterized by the highly seismic Baikal rift zone.The information within the database for each fault segment is organized as distinct but intercorrelated sections（tables,texts and pictures,etc.）and can be easily visualized as HTML pages in offline browsing.The preliminary version of the database distributed free on disk already highlights the general fault pattern showing that the Holocene and historical activity is quite uniform and dominated by NE-SW and nearly E-W trending faults;the former with a prevailing dip-slip normal kinematics,while the latter structures are left-lateral strike-slip and oblique-slip（with different proportion of left-lateral and normal fault slip components）.These faults are mainly concentrated along the borders of the rift basins and are the main sources of moderate-to-strong（M≥5.5）earthquakes on the southern sectors of East Siberia in recent times.As a whole,based on analyzing the diverse fault kinematics and their variable spatial distribution with respect to the overall pattern of the tectonic structures formed and/or activated during the late Pliocene-Quaternary,we conclude they were generated under a regional stress field mainly characterized by a relatively uniform NW-SE tension,but strongly influenced by the irregular hard boundary of the old Siberian craton.The obtained inferences are in an agreement with the existing models of the development of  相似文献   

西西伯利亚东南部早凡兰吟期孢粉地层学,古环境和植被再造     

Ekaterina B.PESTCHEVITSKAYA  Irina V.SMOKOTINA  Galina E.BAYKALOVA 《地层学杂志》2012,(2):179-192

分析了西西伯利亚东南地区的下凡兰吟阶的两个剖面的陆相孢粉型化石的分布。依据西伯利亚北部已经定年的剖面中动物群建立起来的孢粉组合的对比,确定了孢粉标志层的定义,并与北方区的菊石带相对应的孢粉组合进行了对比。这一工作为早凡兰吟期与气候变化息息相关的植被和景观的短期变化以及周边古盆地变迁的重建,提供了地层依据。欧亚大陆中部和东部地区凡兰吟期孢粉组合的横向对比显示:西西伯利亚东南地区的植被具有印度欧洲和西伯利亚加拿大两大古植物地理区的过渡性质,显有这两区的典型特征。  相似文献   

西伯利亚西部白垩纪孢粉的参照序列:演化阶段,相和对比     

Natalia K.LEBEDEVA  Ekaterina B.PESTCHEVITSKAYA 《地层学杂志》2012,(2):193-212

研究西伯利亚西部白垩纪沉积层的孢粉可以建立孢粉组合的参照序列。本文运用采自海相剖面的材料与菊石化石带进行对比,建立了下白垩统和上白垩统一些层位中的孢粉化石带。这些新确立的孢粉组合层序反映了白垩纪孢粉植物群的演化阶段。由于生物相和古地理特征的变化,孢粉组合在横向上变化较大,很难依据孢粉资料进行地区间的精确对比。然而,有些孢粉组合演化发展的总体趋势能用于对比、定义部分地层层位。  相似文献   

Age and origin of charoitite,Malyy Murun massif,Siberia, Russia     

《International Geology Review》2012,54(8):1007-1019

Сharoitite consists of gem-quality mineral charoite and subordinate quartz, aegirine, K-feldspar, tinaksite, canasite, and some other minerals. This rock type is known only from one locality in the world associated with the Early Cretaceous (131.3 ± 2.4 Ma, K–Ar age) Malyy Murun syenite massif, Siberia, Russia. Although charoitite mineralogy is well known, there is disagreement whether it reflects metasomatic or magmatic activity. In order to understand when the charoitites formed we attempted to date it by ⁴⁰Ar/³⁹Ar incremental step-heating and laser ablation techniques. Our results show that the fibrous structure of water-bearing charoite does not retain radiogenic argon. Laser ablation ⁴⁰Ar/³⁹Ar for K-feldspar and tinaksite from the charoitite yielded several age clusters even from the same mineral grain. The oldest cluster of 134.1 ± 2.9 Ma for the K-feldspar agrees with the age of the Malyy Murun syenites. The youngest age of 113.3 ± 3.4 Ma for charoitite K-feldspar overlaps with the youngest of published K–Ar ages (112 ± 5 Ma) for one K-feldspar sample of the Malyy Murun syenite. Tinaksite is characterized by a similar spread of ages (from 133.0 ± 3 Ma to 115.7 ± 4.3 Ma) within a single grain. We suggest that charoitites originated due to the interaction of metasomatic agents derived from the Malyy Murun magma and country rocks. Timing of magma emplacement and charoitite crystallization is reflected by the older cluster of ages, whereas the younger ages are due to a secondary process.  相似文献   

Late Quaternary marine-based Kara Sea ice sheets: a review of terrestrial stratigraphic data highlighting their formation     

Ólafur Ingólfsson  Per Möller  & Hanna Lokrantz 《Polar research》2008,27(2):152-161

Reconstructions of the Late Quaternary glacial history of the Kara Sea area show repeated build-up of ice-sheet domes over the shallow epicontinental Kara Sea. Inferred ice divides were situated over the central Kara Sea, and the ice sheet repeatedly inundated the surrounding coastal areas of western Siberia. Geological fingerprinting of the Kara Sea ice sheet include end moraine zones, raised beaches, tills, glaciotectonic deformations and coarsening-upward sediment sequences, reflecting isostatic rebound cycles. This paper reviews evidence from several areas along the perimeter of the Kara Sea, suggesting that peripheral sites were critical for the initiation of the large Kara Sea ice sheet. Ice-sheet inception progressed with the formation of local ice caps that later coalesced on the adjacent shelf with globally falling sea levels, eventually merging and growing into a large ice dome.  相似文献   

波罗的与西伯利亚板块古生代运动学特征对比新认识     

傅臣建  李江海 《高校地质学报》2012,18(2):280-290

       古地磁学是进行古板块运动演化过程和古地理重建研究最有效的定量方法之一。在统计全球古地磁数据库（GPMDB） 和前人发表数据的基础上,根据国际上通用的古地磁数据可靠性判别标准--Van der Voo （1990）判据,本文对波罗的板 块（Baltica）和西伯利亚板块（Siberia）古生代古地磁数据进行了重新分析和筛选,利用GMAP 软件重建了两个板块古生代 视极移曲线和古地理方位,对它们的构造演化和运动学特征进行对比分析,获得了几点新认识,即两板块在古生代期间发 生的三次汇聚（晚奥陶世、早石炭世和晚二叠世）过程符合牛顿运动学原则（板块之下是具有很大粘度的地幔软流圈,非 理想条件下不可能完全遵守牛顿运动学原则）,且具有三种不同类型的运动学现象：晚奥陶世（~450 Ma）,波罗的和西伯利 亚板块同向北漂移并汇聚,纬向速度较快的板块波罗的将动能传给了纬向速度较慢的西伯利亚板块;早石炭世（~360 Ma）, 波罗的和西伯利亚板块相向漂移并汇聚,西伯利亚板块向南的板块纬向速度转为向北,波罗的板块向北的纬向速度逐渐减 小并转为向南;晚二叠世（~255 Ma）,波罗的和西伯利亚板块再次相向漂移并汇聚,动能抵消,纬向漂移速率都变为零。  相似文献   

Quaternary paleolake formation and cataclysmic flooding along the upper Yenisei River     

Goro Komatsu  Sergei G. Arzhannikov  Alan R. Gillespie  Raymond M. Burke  Hideaki Miyamoto  Victor R. Baker 《Geomorphology》2009,104(3-4):143-164

A suite of geomorphological and sedimentological features in the catchment of the upper Yenisei River in the Sayan mountains of southern Siberia testifies to the occurrence of cataclysmic floods that flowed down the river. Evidence of large-scale high-energy flood events includes: 1) gravel dunes, up to a few meters high and spaced 50 to 80 m apart, in the Kyzyl Basin 2) landforms such as hanging valleys and paleochannels and 3) flood sediments in a tributary valley. The origins of the Yenisei floods were likely diverse due to complex hydrological processes operating in the Sayan mountains. The possibilities include failures of multiple, variably impounded (ice, sedimentary, tectonic scarp, and lava flow dams) paleolakes in the two large intermontane basins of Darkhadyn Khotgor and Todza, and other minor basins, in the upper Yenisei River catchment. Dating techniques applied to the paleolakes in the Darkhadyn Khotgor and Todza basins revealed their formation during various periods in the middle–late Pleistocene and Holocene. Flooding from the Darkhadyn Khotgor appears to explain many of the inferred flood features, although contributions by flooding from other paleolake basins cannot be ruled out. Computer simulation of the flooding caused by a Darkhadyn Khotgor paleolake ice-dam failure indicates a probable peak discharge of  3.5 × 10⁶ m³ s^− 1, approximately one-fifth that of the floods that formed the Channeled Scabland in the U.S.A. Many of the outburst events probably occurred in the late Quaternary, but earlier floods could also have occurred.  相似文献