Vendian of the Fore-Yenisei sedimentary basin (southeastern West Siberia)

Fossiliferous Upper Vendian strata are discovered in the Upper Proterozoic to Lower Paleozoic Fore-Yenisei sedimentary basin under a thick Mesozoic-Cenozoic cover in southeastern West Siberia. Two depositional systems are recognized based on sedimentological features: (1) wave- and current-agitated shoreface-forereef-biohermal reef system (Vostok-3 Borehole section) and (2) tidal flat-evaporite basin (Averinskaya-150 Borehole section). The forereef facies yielded fossilized tubular calcareous skeletons of reef-building metazoans Cloudina riemkeae, Cloudina hartmannae and Cloudina carinata, phosphatized Namacalathus-like fossils, and a diversity of tubular phosphatized and agglutinated tubular fossils. The fossil assemblage can be interpreted as the evidence of ecological complexity of the reef system. Paleontological characteristics suggest correlation of the Vendian strata with the lowermost Purella antiqua Assemblage Zone and the boundary interval with the underlying Anabarites trisulcatus Assemblage Zone of the Siberian Platform. Therefore, at least in the late Proterozoic, the Fore-Yenisei sedimentary basin was part of a larger pericratonic depositional system on the western margin of the Siberian Craton.     

The Middle and Upper Eocene sections of the Omsk trough, West Siberian Platform: Palynological, stratigraphic, hydrologic, and climatic aspects

The thorough analysis and correlation of Middle-Upper Eocene sections in the Omsk trough (southern West Siberian Platform) recovered by Borehole 9 in its axial part near the Chistoozernoe Settlement (Novosibirsk region) and Borehole 8 on the southern limb near the Russkaya Polyana Settlement (southern Omsk region) revealed hiatuses at the base and top of the Russkaya Polyana Beds, a lithostratigraphic unit defined in the Lyulinvor Formation based on its substantially fine-grained composition and poor siliceous microplankton fossil remains. The overlying Tavda Formation (Middle-Upper Eocene) is traditionally accepted to consist of two subformations. The last formation was deposited in the West Siberian inner sea isolated from the Arctic basin. Particular attention is paid to eustatic sea level fluctuation especially during the period marked by accumulation of Azolla Beds under considerable desalination of surface waters in the basin. The curve of variations in the open sea factor based on the quantitative ratio between organic-walled phytoplankton fossils and higher plant palynomorphs is correlated with the modified version of the wellknown Vail curve. It is established that the West Siberian sea level experienced a brief rise in the terminal late Eocene prior to its complete desiccation at the Eocene-Oligocene transition because of global regression in response to glaciation in Antarctica.     

Petroleum Habitat of East Siberia,Russia

East Siberia comprises three petroleum provinces—Lena-Tunguska, Lena-Vilyuy, and Yenisey-Anabar—that occupy the area of the Siberian craton. Petroleum has been generated and has accumulated in Precambrian rifts beneath the sedimentary basins and, more importantly, within the section of the basin itself. The platformal deposits of the basins extend beneath overthrusts on the east and south and are covered by sedimentary rocks of the West Siberian overthrusts on the east and south and are covered by sedimentary rocks of the West Siberian province on the west. Permafrost and gas hydrate deposits are present throughout most of East Siberia.

In the Lena-Tunguska province, rifts that developed during Riphean time are filled by thick sedimentary rocks, in which petroleum deposits have formed. In Early Cambrian time a barrier reef extended across the East Siberian craton from southeast to northwest. A lagoon to the west of this reef was the site of thick rhythmic salt deposits, which are the main seal for petroleum in the province. The sedimentary section of the platform cover ranges in age from Late Proterozoic to Permian. More than 25 oil and gas fields have been discovered in the province, all in Riphean through Lower Cambrian rocks.

The Lena-Vilyuy province includes the Vilyuy basin and the Cis-Verkhoyansk foredeep. During Middle Devonian time, a rift formed along the axis of what was to become the Vilyuy basin. This rift is filled by Upper Devonian and Lower Carboniferous basalt, elastics, carbonates, and evaporites. During this rift stage the region that was to become the Cis-Verkhoyansk foredeep was an open geosynclinal sea. The sedimentary cover consists of Permian, coal-bearing sedimentary rocks as well as elastics from the Lower Triassic, Lower Jurassic, Lower Cretaceous, and Upper Cretaceous, the latter only in the Vilyuy basin. In the Lena-Vilyuy petroleum province as many as nine gas and gas-condensate fields have been discovered.

The Yenisey-Anabar province is largely an extension of the West Siberian petroleum province. Permian sedimentary rocks are present only in the east, where they consist of elastics and some salt. The Triassic, Jurassic, and Cretaceous each are represented by thick clastic deposits. Total thickness of the sedimentary cover is up to 15 km on the west and 8 km on the east. Twelve gas and gas-condensate fields have been discovered in the western part of the province.     

Deep structure of the South Kara sedimentary basin

The structure and evolution of the passive continental margins of the Arctic Ocean are considered on the example of the South Kara Basin. Its development is associated with the evolution of the West Siberian Plate and the formation of the Arctic Ocean. Until the Late Cretaceous, the South Kara Basin was the north margin of the West Siberian Plate, whose formation is related to the Permian–Triassic processes of riftogenesis accompanied by the eruptions of traps. In the Mesozoic, due to the opening of the Arctic Ocean, the South Kara basin became a part of the continental margin, where the accumulation of marine sandy–clayey rocks continued.     

新疆东准噶尔地区构造演化及主要成矿期

笔者认为东准噶尔地区曾是古新疆克拉通的一部分,只是到了泥盆纪才演化成大洋。值得特别提出的是,大洋消失之后,经历了残留海盆阶段才开始碰撞造山。碰撞期后的岩浆作用和板内裂陷作用在该区特别发育,而且形成相关的内生金属矿产。以大型内陆盆地沉降和山脉隆升为特征的陆内造山作用标志着大陆克拉通化的最终完成。成矿期与构造演化密切相关,自老而新划分了6个成矿期。     

青藏高原东缘龙门山晚新生代走滑挤压作用的沉积响应

成都盆地位于青藏高原东缘,夹于龙门山与龙泉山之间,盆地的长轴方向平行于龙门山,呈现为北东—南西向展布的线性盆地。盆地中充填了3.6Ma以来的半固结—松散堆积物,最大厚度为541 m,在垂向上由下部的大邑砾岩、中部的雅安砾石层和上部的上更新统至全新统砾石层组成,其与下覆地层均为不整合接触,显示该盆地是一个单独的成盆期,并非是在中生代前陆盆地基础上形成的继承性盆地。在垂直于龙门山造山带方向上,成都盆地具不对称的楔形结构,沉积基底面整体向西呈阶梯状倾斜,盆地中充填的碎屑物质均来源于盆地西侧的龙门山,具横向水系和单向充填的特征;而且盆地的沉降中心具有逐渐向远离造山带方向迁移的特征,显示盆地的挤压方向垂直于龙门山主断裂,造成了成都盆地在垂直于造山带方向上的构造缩短。在平行于龙门山造山带方向上,成都盆地具有一系列的北东向延伸的次级凸起和凹陷,凹陷和凸起相间分布,且在空间上呈斜列形式展布于盆地的底部,其中次级凹陷（沉降中心）和冲积扇具有向平行龙门山造山带方向迁移的特征,表明成都盆地西缘的龙门山断裂具有右旋走滑的特征。鉴于以上特征,认为成都盆地是在龙门山造山带晚新生代走滑与逆冲的联合作用下形成的走滑挤压盆地。     

Upper Devonian depositional system of Bel’kov Island (New Siberian Islands): An intracontinental rift or a continental margin?

The archipelago of New Siberian Islands situated on the northeastern continental shelf of Eurasia is considered a part of an exotic terrane that collided with Siberia in the Early Cretaceous. Bel’kov Island is located close to the inferred western boundary of this terrane and thus should demonstrate attributes of its localization at the margin of the Paleozoic oceanic basin. The Upper Devonian section on Bel’kov Island is a continuous sequence of deepwater terrigenous rocks, which indicates a tendency toward deepening of the basin previously revealed on adjacent Kotel’ny Island. The lowermost Upper Devonian unit on Bel’kov Island is represented by thin Domanik-like strata resting on the Middle Devonian carbonate platform. The main body of the Upper Devonian sequence, more than 4 km in total thickness, is made up of gravity-flow sediments including turbidites, clay and block diamictites, and olistostromes in the upper part of the section, which accumulated at the slope of the basin or its rise. At many levels, these sediments have been redeposited by along-slope currents. The uppermost unit of organogenic limestone is evidence for compensation of the trough. According to conodont assemblages, the deepwater terrigenous rocks were deposited from the early Frasnian to the early Tournaisian. This time is known for extensive rifting in the eastern Siberian Platform. The data obtained allowed us to reconstruct a NNW-trending Late Devonian rift basin on the Laptev Sea shelf similar to other rifts at the eastern margin of the Siberian Platform.     

The Plio-Pleistocene glaciation of the Barents Sea–Svalbard region: a new model based on revised chronostratigraphy

Based on a revised chronostratigraphy, and compilation of borehole data from the Barents Sea continental margin, a coherent glaciation model is proposed for the Barents Sea ice sheet over the past 3.5 million years (Ma). Three phases of ice growth are suggested: (1) The initial build-up phase, covering mountainous regions and reaching the coastline/shelf edge in the northern Barents Sea during short-term glacial intensification, is concomitant with the onset of the Northern Hemisphere Glaciation (3.6–2.4 Ma). (2) A transitional growth phase (2.4–1.0 Ma), during which the ice sheet expanded towards the southern Barents Sea and reached the northwestern Kara Sea. This is inferred from step-wise decrease of Siberian river-supplied smectite-rich sediments, likely caused by ice sheet blockade and possibly reduced sea ice formation in the Kara Sea as well as glacigenic wedge growth along the northwestern Barents Sea margin hampering entrainment and transport of sea ice sediments to the Arctic–Atlantic gateway. (3) Finally, large-scale glaciation in the Barents Sea occurred after 1 Ma with repeated advances to the shelf edge. The timing is inferred from ice grounding on the Yermak Plateau at about 0.95 Ma, and higher frequencies of gravity-driven mass movements along the western Barents Sea margin associated with expansive glacial growth.     

湖南慈利江垭剖面二叠系-三叠系界线层序的沉积微相类型、沉积环境和海平面变化

本文对湖南慈利江垭剖面二叠系-三叠系界线层序(大隆组顶部9.4m和大冶组底部7.5m)进行了详细的沉积微相分析,划分出八种微相类型,并结合露头和光面上的沉积特征,对每种微相的成因和沉积环境进行了分析和讨论。在此基础上,研究了界线附近的沉积环境和相对海平面变化。大隆组顶部层序沉积于相对海平面持续上升阶段,随着相对海平面的上升,沉积环境逐渐由盆地边缘向盆地内部迁移。在大隆组最顶部,相对海平面有一快速的大幅度下降,沉积环境由深水盆地突然转变为浅水台地。之后自大冶组底部向上,相对海平面又逐渐上升,沉积盆地依次经历了滞流盆地、半循环盆地和循环盆地的转换;在距离大冶组底部约7m处,相对海平面开始下降,气候变得极为干燥,沉积盆地转变为蒸发盆地。值得指出的是,大隆组-大冶组界线处的快速海退面正好对应于二叠纪末生物灭绝面,从而表明大海退很可能是造成二叠纪末生物大灭绝的重要原因。     

始新统-渐新统界线全球变冷事件在柴达木盆地中的记录

以高分辨率磁性地层学为基础,精确地厘定了柴达木盆地西北缘红三旱剖面上、下干柴沟组沉积地层的时代、沉积速率,揭示出36Ma前后柴达木盆地经历了一次短暂的构造活动引起的沉积速率增大,与60～40Ma期间印度板块与欧亚大陆碰撞造成阿尔金断裂再次强烈活化,促使柴达木盆地西北缘山脉形成紧密相关。综合分析沉积物的岩相学、砂岩成分、稳定同位素等与始新统—渐新统界线全球变冷事件的相关性,表明该地区的沉积物记录了始新统—渐新统界线全球变冷事件。     

西昆仑—塔里木—天山岩石圈深地震探测综述

沿新疆地学断面走廊域实施了3种深地震探测方法：近垂直深地震反射剖面、宽角反射与折射深地震测深剖面和移动式宽频地震观测，揭露出西屁仑-塔里木-天山岩石圈的结构与横向变化，发现了塔里木大陆地块与青藏高原西北部西昆仑造山带碰撞的地震学证据，揭示出天山与塔里木、天山与准噶尔，以及昆仑山与塔里木之间的岩石圈尺度盆山耦合关系。阶段成果发表后引起国内外学者广泛注意，本文结合相关资料对这些新成果进行了系统综述，旨在对比研究青藏高原南北两缘不同的碰撞变形之深部过程。     

新疆乌恰县萨热克铜矿床地质特征及硫、铅同位素地球化学

萨热克铜矿是塔里木盆地西北缘中新生界沉积盆地内的大型矿床。矿床定位于托云中生代拉分盆地西缘与东阿赖海西晚期深海盆之间的萨热克巴依中生代断陷盆地内,矿体呈层状、透镜状分布于上侏罗统库孜贡苏组上段(J3k2)灰绿色砾岩层位中,矿石矿物主要为辉铜矿、孔雀石,围岩蚀变较弱。矿石中辉铜矿3δ4S=-24.0‰~-19.0‰,指示硫来自地层中大量硫酸盐的生物还原作用,辉铜矿206Pb/204Pb比值范围为18.475~18.642,207Pb/204Pb为15.606~15.676,208Pb/204Pb为38.585~38.795,指示成矿金属来自于上地壳和造山带剥蚀区。结合矿床地质及地球化学研究,判断萨热克铜矿是与盆地流体活动相关的砾岩型铜矿。     

鄂尔多斯盆地马五5亚段沉积微相分布及演化

岩性及沉积环境的差异是鄂尔多斯盆地下奥陶统马家沟组马五5亚段储层非均质性的重要因素,根据岩石类型、沉积构造及颜色等特征及其与沉积微相的关系,研究区马五5亚段可分为盆缘坪和台内盆地两个亚相及缘内（膏）云质洼地、缘内云坪、缘内灰坪、缘内云灰-灰云坪、盆地（膏）云质洼地、灰云-云灰质盆地及灰质盆地等微相。沉积微相平面上表现为,马五52时期,鄂尔多斯盆地基底抬升,中央古隆起带露出水面;北部地区发育缘内云坪-云质洼地、缘内灰云-云灰坪和灰质盆地;西部地区为缘内云坪-云质洼地、缘内灰云-云灰坪;中部地区为灰质盆地,间夹云灰盆地及盆内云质洼地;马五51时期,北部地区主要发育缘内云坪-云质洼地;西部地区为缘内云坪-云质洼地;中部地区为灰质盆地及盆内云质洼地。盆缘坪和台内盆地的低洼处有利于发生同生期后回流渗透白云化作用,对生成较大规模的泥粉晶白云岩具有重要的意义。      

俄罗斯库页盆地地质、地球物理研究进展

鄂霍茨克海是西太平洋沿岸最北的边缘海,库页盆地是研究该边缘海地质问题最好的窗口.在已有的工作基础上,分析了库页盆地的地球物理场特征;详细讨论了库页盆地的沉积特点、深部结构和地质特征;并对库页盆地地质演化进行了初步的探讨.对库页盆地的研究结果,将对鄂霍茨克海以及中国边缘海盆有很好的帮助和借鉴作用。     

新疆东准噶尔地区构造演化及主要成矿期

笔者认为东准噶尔地区曾是古新疆克拉通的一部分,只是到了泥盆纪才演化成大洋。值得特别提出的是,大洋消失之后,经历了残留海盆阶段才开始碰撞造山。碰撞期后的岩浆作用和板内裂陷作用在该区特别发育,而且形成相关的内生金属矿产。以大型内陆盆地沉降和山脉隆升为特征的陆内造山作用标志着大陆克拉通化的最终完成。成矿期与构造演化密切相关,自老而新划分了6个成矿期。     

典型逆掩断裂带油气富集规律与准噶尔盆地西北缘勘探思路

通过系列调研资料总结得出,世界典型逆掩断裂带的油气具有在沿断裂带应力集中部位、次级构造、基岩断块风化壳以及靠生油凹陷一侧的斜坡区、断裂下盘的有利圈闭中富集的规律.在此基础上,指出准噶尔盆地西北缘的勘探潜力非常巨大,还有约13?08 m3的油气地质储量有待发现;在勘探思路上要系统查明西北缘断裂带,圈定探明程度较低的有利勘探区域和层位以及目前还未进行勘探的有利区块或构造;勘探重点应放在勘探程度较低的有利区块斜坡区和主断裂下盘,并进行深入细致的探测和综合研究工作,以期找到新的储量增长点.     

A mantle plume origin for the Siberian traps: uplift and extension in the West Siberian Basin, Russia

The West Siberian Basin (WSB) records a detailed history of Permo-Triassic rifting, extension and volcanism, followed by Mesozoic and Cenozoic sedimentation in a thermally subsiding basin. Sedimentary deposits of Permian age are absent from much of the basin, suggesting that large areas of the nascent basin were elevated and exposed at that time. Industrial seismic and well log data from the basin have enabled extension and subsidence modelling of parts of the basin. Crustal extension (β) factors are calculated to be in excess of 1.6 in the northern part of the basin across the deep Urengoy graben. 1-D backstripping of the Triassic to Cenozoic sedimentary sequences in this region indicates a period of delayed subsidence during the early Mesozoic. The combination of elevation, rifting and volcanism is consistent with sublithospheric support, such as a hot mantle plume.

This interpretation accords with the geochemical data for basalts from the Siberian Traps and the West Siberian Basin, which are considered to be part of the same large igneous province. Whilst early suites from Noril'sk indicate moderate pressures of melting (mostly within the garnet stability field), later suites (and those from the West Siberian Basin) indicate shallow average depths of melting. The main region of magma production was therefore beneath the relatively thin (ca. 50–100 km) lithosphere of the basin, and not the craton on which the present-day exposure of the Traps occurs. The indicated uplift, widespread occurrence of basalts, and short duration of the volcanic province as a whole are entirely consistent with published models involving a mantle plume. The main argument against the plume model, namely lack of any associated uplift, appears to be untenable.     

Composition and depositional environments of the Upper Jurassic-Lower Cretaceous Mar’yanovo formation (Southeastern West Siberian Sea Basin)

The study of the composition and depositional environments of sediments from the Mar’yanovo Formation (Upper Jurassic-Lower Cretaceous Bazhenov and Georgiev horizons) recovered by boreholes Vostok-1 and Vostok-3 in the southeastern part of the West Siberian Sea Basin revealed the following fact: in the latter hole located closer to the basin boundaries as compared with the former one, they are characterized by lower organic carbon and pyrite contents, indicating reduced salinity of the basin and higher oxidation degree of sediments. The same trend is derived from comparison of rocks from the Mar’yanovo Formation in both holes with the over- and underlying strata. In Borehole Vostok-4, the closet one to the former shoreline of the basin, the Mar’yanovo Formation is indistinguishable. Intense chemical weathering of rocks in provenances during their deposition noted by Kontorovich et al. (1971) is considered a most important factor responsible for its composition and formation conditions. Elevated influx of dissolved weathering products into the sea basin intensified its biogenic activity and stimulated the accumulation of high organic matter concentrations. This inference is valid for all Upper Jurassic-Lower Cretaceous organic carbon-rich sediments that are synchronous to the Mar’yanovo Formation and developed over a spacious area of the West Siberian basin.     

Depositional controls on glaucony texture and composition, Upper Jurassic, West Siberian Basin

This study examines textural inhomogeneity and variable chemical composition of Upper Jurassic glaucony in relation to small‐scale synsedimentary and postsedimentary authigenic processes controlled by the palaeonvironmental and palaeogeographical context. Four glaucony types with complex textural and compositional features have been recognized in cores of the Georgiev Formation of the West Siberian Basin. Samples exclusively made of light green type 1 glaucony (K₂O < 6·5%: the less mature type, richer in glauconite–smectite mixed layer) formed under dysoxic conditions in the deepest distal marine environments of the northern sectors of the West Siberian Basin. Dark green type 2 glaucony is the most mature (richest in glauconitic mica: K₂O up to 8·5%), is sometimes associated with type 1 glaucony, and is typical of high bottom areas with a low sedimentation rate within the central sectors of the basin. Type 3 glaucony is formed by brown grains, poorer in K and Fe but richer in Al and Si than type 2 glaucony, and is only present in strongly condensed successions of the central‐eastern sectors of the West Siberian Basin. Type 4 glaucony is much richer in Fe than any other type, shows fresh yellowish green cores slightly less mature than type 2 glaucony, and brown rims and cracks with composition similar to that of type 3 grains; it was formed in western sectors of the West Siberian Basin, close to Urals. Weathering under a subtropical to temperate climate, and erosion of badly drained peneplaned lowland areas around the basin, provided Al‐rich terrigenous clays as substratum for glauconitization, which explains Al and Si enrichment in Siberian glaucony. Maturation from glauconite–smectite to glauconitic mica is monitored by a change from light to dark green colour related to decrease in Al, Si, Mg, Ca and Na, and to increase in K and Fe. Brown rims of type 4 glaucony, and brown type 3 grains formed after leaching of Fe and K from mature glauconite, with formation of clays and Fe oxyhydroxides as reaction products, as a result of free oxygen exposure related to a hydrodynamic regime and temporary sea‐level fall. Glauconitization stopped and diagenetic pyrite formed due to basin deepening and burial under black shales during the latest Jurassic–earliest Cretaceous transgression. This study demonstrates that, due to the complex nature of glaucony, the authigenesis of glauconitic minerals in the rock record cannot be correctly understood if the palaeoenvironmental context and the palaeogeographical context of glaucony‐bearing sediments are not considered.