The Yudomian of Siberia,Vendian and Ediacaran systems of the International stratigraphic scale     

V. V. Khomentovsky 《Stratigraphy and Geological Correlation》2008,16(6):581-598

In Russia, the terminal Neoproterozoic formally includes the Vendian of western part of the East European platform and the concurrent Yudoma Group of Siberia. As is shown in this work, the designated subdivisions correspond in the stratotypes only to the upper, Yudomian Series of the Vendian. In the Siberian platform, the Ust-Yudoma and Aim horizons of the Yudomian are tightly interrelated. The lower of them, bearing remains of Ediacaran Fauna, represents the Ediacarian Stage, whereas the upper one containing small-shelled fossils (SSF) corresponds to the Nemakit-Daldynian Stage divided into the trisulcatus and antiqua superregional zones. In more complete sections of the platform periphery, sediments of these subdivisions conformably rest on siliciclastic succession that should be ranked as basal subdivision of the Yudomian. The succession is concurrent to the Laplandian Stage of the East European platform. According to geochronological dates obtained recently, the Yudomian Series spans interval of 600–540 Ma. In the East European platform, the Upper Vendian (Yudomian) begins with the Laplandian basal tillites of synonymous stage. In the west of the platform, tillites are dated at 600 Ma like the Upper Vendian base in Siberia. The next Ediacarian Stage of the East European platform is stratigraphic equivalent of the Redkino Horizon, while summary range of the Kotlin and Rovno horizons is concurrent to that of the Nemakit-Daldynian Stage. The Vendian of Russia is conformably overlain by the Tommotian Stage of the Lower Cambrian. Intense pre-Vendian events constrained distribution areas of the Lower Vendian sediments in Russia. The Lower Vendian deposits of the East European platform are most representative and well studied in the central Urals, where they are attributed to the Serebryanka Group. In Siberia, separate subdivisions representing the Lower Vendian are the Maastakh Formation of the Olenek Uplift, two lower members of the Ushakovka Formation in the Baikal region, and the Taseeva Group of the Yenisei Range. Chronological interval of the Lower Vendian corresponds to 650–600 Ma. The Marinoan Glaciation dated in Australia at 650–635 Ma is concurrent to basal part of the pre-Yudomian interval of the Vendian in Russia, whereas the Laplandian Tillite and Gaskiers Glaciation (600–580 Ma) correspond to onset of the Yudomian Epoch. The new Ediacaran System (Knoll et al., 2004) legalized in the International Neoproterozoic scale is close in range to the entire Vendian (635–544 Ma), although without basal beds (Marinoan Tillite) it deprives the terminal Neoproterozoic of its original sense. Inferiority of the system consists also in its indivisibility into stages. Hence, it is clear that the Vendian System subdivided in detail in Russia should be retained in the rank of terminal system of the Precambrian, one of the basic in general scale of the Neoproterozoic.  相似文献   

Contamination patterns and molluscan and polychaete assemblages in two Persian (Arabian) Gulf oilfields          下载免费PDF全文

Paolo G. Albano  Nadezhda Filippova  Jan Steger  Hannah Schmidbaur  Adam Tomašových  Michael Stachowitsch  Martin Zuschin 《Marine Ecology》2016,37(4):907-919

This study examined two shallow‐water, offshore oil facilities and their surroundings in the Umm Al Dalkh and Zakum oilfields [United Arab Emirates, Persian (Arabian) Gulf]. The focus was on sediment contamination levels and the detection of disturbance based on two representative invertebrate components of the benthos: molluscs and polychaetes. We tested the hypothesis that significant disturbance to the community has occurred, by examining whether distance from the platform or variation in contaminants explains among‐site variation in the composition of benthic communities. Moreover, we also tested the hypothesis that organic enrichment because of oil input has modified the feeding guild structure by examining whether the relative abundances of filter‐feeders, deposit‐feeders and omnivores are correlated with distance from the platform or with contamination by hydrocarbons. The contamination levels and their spatial distribution in the sediments differed significantly between the two fields, as did their mollusc and polychaete communities. The within‐field variability, however, was much lower: no clear structuring of contamination values and species composition and abundance was detectable in relation to distance from the oil platform. Contamination levels were low, often below detection levels or international guideline values. Variation in contaminant concentrations did not explain variation in taxonomic composition and abundance. The relative abundance of the above‐mentioned feeding guilds did not correlate with either distance from the platform or with contaminant concentrations. These patterns may reflect the long time that has elapsed since drilling (15–20 years), which appears to have allowed contaminants to disperse and degrade and assemblages to recover from the impact, if indeed such a disturbance ever occurred. In contrast to low values of barium and total petroleum hydrocarbons, associated with well drilling, some metals were at their highest concentrations beneath the central platforms. This suggests that production‐related activities (including platform cleaning and maintenance) are currently a more relevant contamination source.  相似文献   

非灌浆导管架平台异常振动的测试分析及故障诊断     

文世鹏王津  黄维平 《海洋工程》2005,23(2):16-20

通过对平台在风浪作用下的振动测试分析,发现了直立式非灌浆桩腿导管架平台在海底冲刷条件下发生异常振动的原因是导管架与桩之间存在较大的相对运动,以至于在风浪较大时发生碰撞。因而,结构的动力特性和动态响应都与设计结果不一致。在非极值海况条件下,平台的振动超出了设计预测值,并提出了治理和设计建议。  相似文献   

倾斜摄影设备选型及像控点布设对高精度实景三维模型重建的影响     

席思远  张西童  王宁  张兆江  李剑明  张国栋 《测绘通报》2022,(10):86-92

在高精度实景三维模型生产中,无人机平台与载荷的选择及像控点布设十分重要,对航摄效率、模型精度、效果均有影响。本文以我国北部某城镇村为研究区域,利用不同的无人机倾斜摄影测量设备分别获取同分辨率倾斜影像,并结合不同的像控点布设方案重建实景三维模型。通过同等分辨率原始影像的不同装备及像控点布设的组合方案构建对照试验组,对比验证并分析飞行效率、模型精度及模型效果,选取满足高精度实景三维模型重建要求的设备类型及经济合理的像控点布设方案,为实际的生产作业提供指导。  相似文献   

Latitudinally different responses of Tethyan shoal‐water carbonate systems to the Early Aptian oceanic anoxic event (OAE 1a)     

STEFAN HUCK  NIELS RAMEIL  TVRTKO KORBAR  ULRICH HEIMHOFER  THOMAS D. WIECZOREK  ADRIAN IMMENHAUSER 《Sedimentology》2010,57(7):1585-1614

Ocean‐wide anoxic events represent intensively investigated anomalies in the global carbon cycle. Most previous research has focussed on hemipelagic and pelagic settings and on the relationship between black‐shale deposition and carbon‐isotope excursions. The study of ocean‐wide anoxic events and coeval shallow‐water settings is now increasingly seen as an interesting complementary approach, but one that is not without problems. Whereas platform drowning characterizes the Early Aptian of the northern Tethyan margin, Lithocodium–Bacinella‐rich facies and ongoing shoal‐water sedimentation at the southern Tethyan margin (Oman) bears important information on potential causes of carbon‐cycle perturbations. The present paper seeks to test the supra‐regional relevance of the Oman data by investigating coeval central Tethyan limestones. Three Lower Aptian shoal‐water sections in Istria (Croatia), deposited on the isolated Adriatic Carbonate Platform, are investigated applying chemostratigraphy (carbon and strontium) and detailed sedimentological analysis. The focus is on peritidal to lagoonal facies characterized by mass occurrences of Lithocodium–Bacinella, an enigmatic microencruster community. Lithocodium–Bacinella facies occurs predominantly in layers ranging from one to several centimetres in stratigraphic thickness, with several layers merging to metre‐thick packages. Growth fabrics within the layers include oncoidal morphotypes, lumps, interconnected patches and columns, layers and rare nodular to massive bindstone facies. These growth patterns show a remarkable regional extent and consistency over study sites distributed several kilometres apart. This widespread distribution suggests that specific Lithocodium–Bacinella morphotypes might serve as regional stratigraphic markers. The high‐resolution carbon‐isotope chemostratigraphy presented here is based on pristine rudist shells and matrix micrite samples and calibrated against strontium‐isotope data obtained from screened rudist low‐Mg calcite. The chemostratigraphic data are consistent with existing biostratigraphic data and place the studied strata at the onset of Early Aptian oceanic anoxic event 1a. Moreover, results indicate the near‐coeval nature of Lithocodium–Bacinella bloom facies in Istria and Oman. The outcomes of this study point to latitudinally different responses of Tethyan shoal‐water carbonate systems (platform drowning versus Lithocodium–Bacinella blooms) to the ocean‐wide anoxic event 1a.  相似文献   

Estrogen receptor (ER) agonists and androgen receptor (AR) antagonists in effluents from Norwegian North Sea oil production platforms   总被引：6，自引：0，他引：6  

Tollefsen KE  Harman C  Smith A  Thomas KV 《Marine pollution bulletin》2007,54(3):277-283

The in vitro estrogen receptor (ER) agonist and androgen receptor (AR) antagonist potencies of offshore produced water effluents collected from the Norwegian Sector were determined using recombinant yeast estrogen and androgen screens. Solid phase extraction (SPE) concentrates of the effluents showed E2 agonist activities similar to those previously reported for the United Kingdom (UK) Continental Shelf (<0.1-4 ng E2 L(-1)). No activity was detected in the filtered oil droplets suggesting that produced water ER activity is primarily associated with the dissolved phase. Targeted analysis for methyl- to nonyl-substituted alkylphenol isomers show the occurrence of known ER agonists in the analysed samples. For the first time, AR antagonists were detected in both the dissolved and oil associated phase at concentrations of between 20 and 8000 microg of flutamide equivalents L(-1). The identity of the AR antagonists is unknown, however this represents a significant input into the marine environment of unknown compounds that exert a known biological effect. It is recommended that further analysis using techniques such as bioassay-directed analysis is performed to identify the compounds/groups of compounds that are responsible in order to improve the assessment of the risk posed by produced water discharges to the marine environment.  相似文献   

基于实测的导管架海洋平台振动对人员安全评价     

车啸飞  张大勇  岳前进  樊哲良 《海洋工程》2011,29(4):68-73

目前我国的海洋工程结构中,导管架式海洋平台占有很大比重,动荷载作用下导管架式海洋平台的振动问题日益突出。随着石油开发向深海进军,平台结构柔性更大,振动问题更为显著,可能对结构、设备及人员造成一定的安全隐患。基于现场监测获得的导管架平台振动响应,结合相关规范给出振动对人体的影响,提出人员感受评价流程。最后,以渤海、南海海域的导管架平台为例,基于现场监测,分析了结构的振动特性及作业人员在相应振动环境下的感受。此方法对导管架平台上部作业人员的工作与安全保障提供了科学依据。  相似文献   

Global and regional factors responsible for the drowning of the Central Apennine Chattian carbonate platforms     

Marco Brandano  Michele Lustrino  Irene Cornacchia  Mario Sprovieri 《Geological Journal》2015,50(5):575-591

This work discusses and interprets the factors responsible for the Oligocene–Miocene drowning of the Central Apennine platform deposits, based on facies and stable‐isotope analyses of two representative stratigraphic sections. The Mediterranean carbonate platforms were affected during the Oligocene–Miocene boundary by a carbonate production crisis that was induced by global factors and amplified by regional events, such as volcanic activity. The positive δ¹³C shift observed in the studied sections corresponds to vertical facies changes reflecting the evolution from middle carbonate ramp to outer ramp‐hemipelagic depositional environments. This drowning event is recorded not only in the Apennine platforms, but also in other Mediterranean platforms such as in southern Apulia, Sicily and Malta, and outside the Mediterranean Basin. The ~24–23.5 Ma Mi‐1 glacial maximum may have had a significant influence on this drowning event because it was associated with high rates of accumulation of continent‐derived sediments. The increased continental weathering and runoff sustained high trophic conditions. These probably were a consequence of the Aquitanian–Burdigalian volcanic activity in the Central‐Western Mediterranean, that may have led to an increase in nutrient content in seawater and an increase in atmospheric and marine CO₂ concentrations. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

基于交互式3维平台的3维GIS数据可视化方法     

黄翌  苏继良  武宜广  王健  李陈 《东北测绘》2011,(6):1-3,6

3维GIS是目前GIS发展的新趋势之一,本文通过分析比较各种3维平台的功能,探讨了利用它们进行交互式数据交换的方法,为展示、发布3维成果提供数据支撑,并展望了利用交互式平台设计3维GIS系统的前景。  相似文献   

Subaerial weathering versus wave processes in shore platform development: reappraising the Old Hat Island evidence     

David M. Kennedy  Ryan Paulik  Mark E. Dickson 《地球表面变化过程与地形》2011,36(5):686-694

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