江西玉山早奥陶世笔石动物群的分带及分异

<正> 江西玉山具有完整的下奥陶统宁国组含笔石地层,陈旭、韩乃仁(1964)建立了下奥陶统笔石带,限于当时的标本采集,分带尚不够精确。1979年秋,笔者与邹西平、李罗照在玉山山头底(李家蓬)、会英亭、牟家坞等地测制剖面,获得了比较可靠的笔石分带。本文     

Biofacies zonation of Ordovician deposits of the southern Siberian Platform

Based on the inventory, revision, and analysis of stratigraphic, paleontological, and lithofacies data on the area of Ordovician deposits in the southern Siberian Platform (Irkut amphitheater), the refined and detailed schemes of biofacies zonation of this paleobasin are substantiated. Schemes of zonation have been compiled for the Nyaian, Ugorian, Kimaian, Mukteian, Volginian, Kirenskian-Kudrinian, Chertovskian, and Baksanian Horizons of the regional Ordovician stratigraphic chart of the Siberian Platform. The schemes present biofacies different in lithologic composition, spread of dominant groups of fauna, and hydrochemical regime (normal-marine salinity, freshwater, or high salinity). It is shown that contrasting changes in paleogeographic environments and the spread of faunal communities under changing environmental conditions were influenced by the transgression-regression cyclicity of the evolution of the Siberian Platform paleobasin and by the proximity of the land. Specific groups of fauna localized in particular facies are described. These groups are regarded as communities that were the first to occupy the littoral zones of epicontinental sea basins in the Ordovician.     

中国首次发现奥陶纪无颌纲古鱼类动物群

2011年5~6月在新疆巴楚县一间房地区南1沟剖面上奥陶统恰尔巴克组首次发现百余件古鱼类化石。根据头甲具有一对眶孔和骨甲具有骨质层结构,将它们确定为无颌纲,并建立了新亚纲1个,新目2个,新科2个,新属新种各4个。鱼类化石赋存于熊剑飞等(2006)在该剖面所作的牙形石Baltoniodus alobatus带中,时代属于晚奥陶世艾家山期早期。根据外部形态特征将这一古鱼类化石群命名为秀丽巴楚鱼-宽吻古盔甲鱼(Bachuiaspis elegans-Palaeogaleaspis platyrostrastus Fauna)动物群。该化石动物群是中国脊椎动物生物证据确凿的记录,也是世界上晚奥陶世早期中国所特有的脊椎动物群。这批化石新材料的发现不仅在古鱼类发生和演化史上,而且在古脊椎动物地理分区和古构造分区上均具有重要的科学价值和研究意义。     

中国首次发现奥陶纪无颌纲古鱼类动物群

2011年5~6月在新疆巴楚县一间房地区南1沟剖面上奥陶统恰尔巴克组首次发现百余件古鱼类化石。根据头甲具有一对眶孔和骨甲具有骨质层结构,将它们确定为无颌纲,并建立了新亚纲1个,新目2个,新科2个,新属新种各4个。鱼类化石赋存于熊剑飞等(2006)在该剖面所作的牙形石Baltoniodus alobatus带中,时代属于晚奥陶世艾家山期早期。根据外部形态特征将这一古鱼类化石群命名为秀丽巴楚鱼-宽吻古盔甲鱼(Bachuiaspis elegans-Palaeogaleaspis platyrostrastus Fauna)动物群。该化石动物群是中国脊椎动物生物证据确凿的记录,也是世界上晚奥陶世早期中国所特有的脊椎动物群。这批化石新材料的发现不仅在古鱼类发生和演化史上,而且在古脊椎动物地理分区和古构造分区上均具有重要的科学价值和研究意义。     

An endemic brachiopod fauna from the Middle Ordovician of North Wales

The brachiopod fauna from the base of the Bryn Siltstone Formation (middle Caradoc), Glyn Ceiriog, north Berwyn Hills, North Wales, consists of Platystrophia elevata sp. nov., Salopia abbreviata sp. nov., Kiaeromena ungula (M'Coy) and unnamed species of Hesperorthis?, Reuschella and Bicuspina. The dominant brachiopod species, Leptaena (Leptagonia) ungula M'Coy, 1851 is revised and its current assignment to the leptaenid genus Kiaeromena confirmed, based on the examination of type and topotype material from the Bryn Siltstone Formation. Kiaeromena spjeldnaesi nom. nov. is proposed to replace the junior homonym K. ungula Spjeldnæs, 1957 for that congeneric species from the upper Caradoc rocks of Ringerike, southern Norway. The fauna as a whole is unusual within the context of the Anglo-Welsh province and may represent a rare preserved nearshore community.     

Formation of gas hydrate deposits in the Siberian Arctic shelf

Natural gas hydrate deposits have been estimated to store about 10% of gas in hydrate form (even with regard to a higher concentration of gas in hydrates), proceeding from the known ratio of dissolved-to-deposited gas. This high percentage is largely due to the fact that the buffer factor in natural gas hydrate deposits is lower than that for free gas because of less diverse structural conditions for gas accumulation. Therefore, the available appraisal of world resources of hydrated gas needs a revision.Hydrates in rocks are either syngenetic or epigenetic. Syngenetic hydrates originate from free or dissolved gas which was present in rocks in situ at the time when PT-conditions became favorable for gas hydrate formation. Epigenetic hydrates are derived from gas which came by migration into rocks with their PT-conditions corresponding to formation of gas hydrates.In addition to the optimum PT-conditions and water salinity, economic gas hydrate accumulation requires sustained supply of natural gas into a specific zone of gas hydrate formation. This condition is feasible only in the case of vertical migration of natural gas along faults, fractured zones, and lithologic windows, or, less often, as a result of lateral migration.Of practical importance are only the gas hydrate deposits produced by vertical or lateral gas migration.     

Ordovician sediments in the southeastern Siberian Platform: lithostratigraphy and ostracod zoning

The results of studying Ordovician ostracods from the southeastern Siberian Platform are presented. Ordovician sections are described in brief from outcrop and core studies. Four of the ostracod zones distinguished in the Ordovician strata of the Siberian Platform have been found in the Volgian, Kirenskian–Kudrinoan, Chertovskayan, and Baksanian Horizons. Stratigraphic correlation takes into account the available data on the distribution of other groups (e.g., conodonts and cephalopods)..     

Formation conditions and stratigraphy of Carboniferous coal deposits of the Siberian Platform

Litbological, paleogeographic, and paleontologic characteristics of the Siberian Platform indicate three stages in the geological development of the region and evolution of its organic world: Early, Middle, and Late Carboniferous, corresponding to the Lower, Middle, and Upper series of the Carboniferous system. Deposits of the lower series, separated as the Anganehan horizon. Include the Anganchan, Kazach'ya, and Krasnognr'yevka suites and lower portions of the Apsekan, Brus, Fat'yanikha, and Kondromo suites. Deposits of the middle series are assigned to the Tushama horizon, which includes the Tushama, Yangoto, Miirma, and Khattynngynakh suites and the Upper portions of the Apsekan, Brus, Fat'yanikha, and Kondromo suites. Formations of the upper series (the Kata horizon) include the Rudnaya, Anaklt, Listvyazhnoye, Kata, and Chokhchuolu suites.—Authors.     

新疆西克尔地区下奥陶统鹰山组岩溶分带性研究

塔里木盆地岩溶缝洞型储层作为重要的油气储层备受关注,而目前预测此类型储层的方法较有限。在新疆伽什县西克尔野外露头区地表岩溶现象丰富,志留系地层以填平补齐的方式充填在一系列的溶沟和溶槽中,部分洼地中还有志留系地层残留,表明该区发育加里东中期岩溶。在本区岩溶古地貌的基础上,基于排泄基准面的分析,划分出3级岩溶台面并对应发育3期岩溶。据现代地貌学和岩溶学理论,按照水动力条件的不同并结合本区岩溶发育特征,运用岩溶旋回的观点将第二期岩溶剖面分为表层岩溶带、垂直渗滤带和水平潜流带,认识到西克尔地区古岩溶地下水发育规律及洞穴发育程度。构造运动是垂向岩溶分带性的主控因素;因此,在大的构造背景的前提下,可以有效地预测巴楚地区的缝洞型储层。     

Evolution of Cambrian to Ordovician trace fossils in pelagic deep-sea chert,Australia

Cambrian to Ordovician pelagic radiolarian cherts in the Lachlan Fold Belt in southeastern Australia contain trace fossils demonstrating the faunal diversification that occurred during the Ordovician on the deep-sea floor. The Cambro-Ordovician Howqua Chert has a very low degree of bioturbation, and the trace fossils are small and shallow. In contrast, the late Middle to Late Ordovician cherts are strongly bioturbated with larger, deeper burrows, and contain more morphologically diverse trace fossils. This records a substantial increase in the size, abundance and activity of deep-ocean benthic animals living on the floor of the ocean bordering Australia.     

Kerogen from the Cambrian deposits of the Kuonamka Formation (northeastern Siberian Platform)

Kerogens from the Lower and Middle Cambrian deposits of the Kuonamka Formation in the northeastern Siberian Platform have been analyzed by modern methods. We have determined the pyrolytic characteristics of insoluble organic matter and the contents of C, H, S, N, O, and the stable C isotope. The type and catagenesis of organic matter have been estimated, as well as the generating potential of oil source rocks. It has been found that the composition of kerogens taken from the Molodo River outcrops was affected by supergene processes and that the degree of their alteration is related to the organic content of rocks and their structure.     

华南下/中奥陶统界线附近笔石动物群的图形对比研究

在下/中奥陶统界线附近笔石的生物地层学研究基础上,笔者选择了华南地区奥陶系台地相、盆地相和位于二者之间的过渡相等不同沉积相区5条典型地层剖面,开展了华南下/中奥陶统界线附近笔石动物群的图形对比研究,通过这项研究,进一步明确了华南奥陶系下/中奥陶统界线附近笔石动物群的延限和不同相区笔石动物群的精确对比关系,为开展不同相区之间地层的精确对比奠定了基础。     

Predicting kimberlite diamond deposits in the north of the Siberian Platform on the basis of interpretation of satellite imagery

An essentially new method for the allocation of diamondiferous kimberlite pipes against surrounding rocks is proposed. The method is based on the interpretation of multispectral LANDSAT-7 ETM+ satellite images; it allows one to find the most promising areas within perspective sites revealed by other methods. It is demonstrated that application of GIS technologies for comprehensive use of geological, geophysical, and mineralogical data and the results of the interpretation of satellite images is efficient for predicting kimberlite diamond deposits in both studied areas and poorly explored territories.     

Carboniferous deposits in the basement of the southwestern West Siberian geosyneclise (Kurgan Region)

The ⁴⁰Ar/³⁹Ar age of volcanics from the sections of core boreholes in the northern Tyumen’-Kostanai trough (Kurgan Region) has been determined. The geologic structure of the northern part of the trough has been refined. The paleogeographic environments and geodynamic settings of formation of Carboniferous deposits have been established by sedimentological, petrological, and geochemical studies of the sections. In the Visean, marine environments with maximum basin depths were predominant. In the Kachar epoch (C1v3-s), the submarine relief of the basin became more complicated; blocks of older rocks appeared in the deposits. The geochemical indicator characteristics of the volcanics—contents of HFSE (Ti, Nb, Ta, Th, and Hf)—are close to those of andesitoids of island arcs and Andean-type active continental margins, as well as present-day andesites from the Kurile-Kamchatka zone. They are an order of magnitude lower than those in similar continental-rift volcanics, among which are volcanics of the Valer’yanovka zone (according to some researchers). The contents of Ni, Co, and V are similar to those in island-arc andesites, including rocks of the Kurile-Kamchatka zone. The Ba/Ta and Ba/La ratios and the proportions of Th, Hf, and Ta in andesitoids of the Valer’yanovka and Kachar Groups are close to the indicator characteristics of island-arc and active-continental-margin volcanics. The Kachar Group siliceous rocks are similar in the Rb/Zr-Nb, Fe-Nb, and Rb-(Y + Nb) correlations to rocks of mature island arcs and active continental margins. The incompatible-element and REE patterns for the Valer’yanovka and Kachar volcanics are typical of island-arc volcanics, including rocks from the Kurile-Kamchatka zone. The indicator geochemical features and petrology of the volcanics and the sedimentologic features of the deposits testify to their formation on an Andean-type active continental margin (western margin of the Kazakhstan paleocontinent) in the Early-Middle Carboniferous.     

宁夏中奥陶统香山群徐家圈组内波和内潮汐沉积*

宁夏中奥陶统香山群为一套遭受轻微区域变质的陆源碎屑岩,并夹有少量碳酸盐岩和硅质岩,主要为深水浊流沉积。其中,徐家圈组主要由灰绿色、黄绿色轻变质细砂岩、钙质砂岩及粉砂岩和页岩组成,顶部发育有薄层石灰岩。在该组的中—薄层钙质粉—细砂岩、细粉屑质石灰岩和粉砂质页岩中发现了双向交错层理及纹层倾向与区域斜坡倾向相反或有较大夹角的单向交错层理,其中双向交错层理形态丰富、纹层清晰,其纹层倾向有沿斜坡向上的,有沿斜坡向下的。在深水环境中,这些交错层理不应是等深流沉积或浊流沉积的产物,而应为内波产生的沿斜坡上下水流交替流动所形成的。从沉积背景、沉积构造和古水流等方面对徐家圈组的内波、内潮汐沉积进行了详细的研究,认为其形成于水道不发育的深水斜坡环境,并对斜坡环境中内波、内潮汐沉积中不发育脉状、波状和透镜状层理的现象进行了解释。     

Perspectives of the discovery of large and unique noble metal deposits in the northeastern Siberian Platform

Geological prospecting indicators of a potential presence of the Witwatersrand-type large and superlarge noble metal deposits containing optional Pt, Ir, Os, Rh, U, and diamond are presented. Perspective areas of native gold concentration in the northeastern Siberian Platform are indicated. Gold metallogeny of this region was basically developed in Early Precambrian in association with greenstone belts and granulitegneiss complexes. Promising zones with noble metal mineralization encompass large areas at the junction of tectonic provinces.