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分布于皖西淮南、霍丘一带的震旦系上统凤台组,是一套以杂砾岩为主的碎屑岩系,其中富含碳酸盐岩成份。在区域上,它与豫西罗圈组层位大致相当。对凤台组杂砾岩的成因,长期存在着几种不同认识,但大多数研究者认为是冰川形成的底碛和冰湖沉积。根据作者对该组杂砾岩的沉积构造、岩石学及地球化学特征的分析研究,认为它的成因颇为复杂,不仅具有冰碛岩的某些特征,而且还有重力流及滑塌沉积的一些特点。因此,凤台组可能是在冰前海湾(冰海)环境中的沉积。总之,这套杂砾岩显示出许多再沉积的特征。 相似文献
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华北板块南缘新元古界罗圈组为一套特殊的杂砾岩层,其是否为冰川成因对于新元古代冰期的研究具有重要意义。在野外实测剖面的基础上,本研究对鲁山地区罗圈组岩性、岩相特征及冰蚀遗迹进行探索,恢复其沉积环境,结果显示:罗圈组底部存在冰溜面,主体为块状杂砾岩,砾石砾径差异较大,呈棱角及次棱角状,地层中含有砂岩透镜体及出现坠石构造;镜下观察砂岩分选磨圆差、颗粒支撑。上述特征说明豫西鲁山地区罗圈组为冰川成因,推断其为陆相冰碛岩及冰水环境形成的产物。本文建立了罗圈组冰川相、冰水相的沉积模式,对于确定该地区古环境、古地理及新元古代冰川发育范围具有一定的参考价值。 相似文献
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青藏高原及其邻区石炭纪—二叠纪地层中广泛分布的漂砾层、杂砾岩、含砾板岩等是一套特殊的冰海相沉积岩,称为冰海杂砾岩,前人已对它的成因环境做了初步的研究,但没有获得统一的结论。本次以青藏高原羌塘南部冈玛错地区冰海杂砾岩的砾石为研究对象,观察它们的野外特征和镜下特点,并对与冰海杂砾岩互层产出的石英砂岩做了粒度分析。结果表明,冰海杂砾岩是在冈瓦纳大陆冰川呈消融状的情况下,冰阀搬运沉积的产物。通过碎屑锆石和岩性对比,初步认为冰海杂砾岩的物源为冈瓦纳大陆,并简单论述了冰海杂砾岩各类砾石的可能来源。以上研究成果为探讨冈瓦纳大陆的沉积环境提供了依据。 相似文献
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青藏高原羌塘南部冰海杂砾岩的成因与物源——以冈玛错地区为例 总被引：4，自引：3，他引：1
青藏高原及其邻区石炭纪—二叠纪地层中广泛分布的漂砾层、杂砾岩、含砾板岩等是一套特殊的冰海相沉积岩,称为冰海杂砾岩,前人已对它的成因环境做了初步的研究,但没有获得统一的结论。本次以青藏高原羌塘南部冈玛错地区冰海杂砾岩的砾石为研究对象,观察它们的野外特征和镜下特点,并对与冰海杂砾岩互层产出的石英砂岩做了粒度分析。结果表明,冰海杂砾岩是在冈瓦纳大陆冰川呈消融状的情况下,冰阀搬运沉积的产物。通过碎屑锆石和岩性对比,初步认为冰海杂砾岩的物源为冈瓦纳大陆,并简单论述了冰海杂砾岩各类砾石的可能来源。以上研究成果为探讨冈瓦纳大陆的沉积环境提供了依据。 相似文献
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位于华北克拉通中部造山带内部的五台杂岩与毗邻的阜平、恒山杂岩是最经典的前寒武纪地质研究地区。被认为该地区最年轻的地质单元滹沱群不整合覆盖于五台和阜平杂岩之上。近来的工作越来越显示出滹沱群对于该地区乃至整个中部造山带的构造演化的重要性。然而对滹沱群沉积岩物源的缺乏认识阻碍了对该区沉积环境和构造意义的进一步研究。本文利用LA-ICP-MS,从滹沱群最底部的花岗质砾岩中获取了U-Pb锆石年龄,结合前人的地层学、地质年代学、构造地质学以及变质作用研究,对该地区底砾岩的沉积物源及大地构造演化提供了新的制约。滹沱群自下而上由底砾岩和火山碎屑岩(豆村亚群)、碎屑岩、板岩、白云岩和大理岩(东冶亚群)以及砂岩和另外一套出露于顶部的砾岩(郭家寨亚群)组成。来自于滹沱群底砾岩的花岗质砾石中的锆石获得了2517~2566Ma的207Pb/206Pb权重年龄,与五台新太古代的花岗岩(2566~2515Ma)年龄一致,说明这些花岗质砾石来源于五台新太古代花岗岩。结合前人的研究,滹沱群很有可能代表了一个发育在西部陆块向东部陆块俯冲过程中与俯冲相关的弧后前陆盆地。该盆地在约1850Ma华北克拉通最终碰撞拼合事件过程中闭合。滹沱群花岗质砾岩的... 相似文献
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西藏拉萨林周地区的下二叠统旁多群的地层层序以前并不十分清楚，其中“杂砾岩”的成因也争议很大。通过详细的野外地质调查和研究，在林周旁多地区新发现了其中部的含有坠石的纹层状粘土岩，并建立了旁多群中部和上部的地层序列。旁多群中部以陆源碎屑少、悬浮泥质为主的欠补偿深水盆地相沉积为特征，而上部以陆源碎屑丰富的滨、浅海相沉积为特征。旁多群自下而上反映了两期岩浆构造事件：第一期发生在该群中部沉积之初，伴随着基性玄武岩的喷发，该群中部沉积时，盆地进入裂谷鼎盛时期，随后进入以旁多群上部为代表的裂谷充填阶段；第二期构造事件可能发生在旁多群和乌鲁龙组沉积之交，乌鲁龙组沉积物中含有大量的长石碎屑、火山岩岩屑和凝灰质沉积岩，指示这期岩浆构造活动的存在。旁多群中的坠石沉积指示旁多群的形成背景是裂谷构造环境下的冰海相。旁多群中的杂砾岩按照成因可以划分为：具有正粒序结构的杂砾岩，为重力流沉积岩，反映侧向水流的搬运；不具有正粒序结构的厚层块状、含有坠石沉积的杂砾岩，为水下冰碛岩，反映冰川、冰筏作用存在，指示大陆上有冰川作用。这种分类和命名有助于石炭-二叠纪冰川发育过程和旋回性的研究，也有助于提高冰海相地层的划分和对比的可靠性和精度。 相似文献
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福建省闽北地质大队变质岩专题研究,在建阳县麻沙镇长坪电站以西发现一套角砾岩称为“长坪砾岩”。对该砾岩的成因有二种看法:一为构造角砾岩;一为沉积变质砾岩叠加后期构造。笔者根据其显微镜下特征,认为属构造角砾岩。主要依据:砾石成分与两侧围岩相同,均为变粒岩、片岩,且在某些部位尚保留与围岩相同的条纹条带状构造;砾石未经分选颗粒大小混杂,磨圆度及球度不一,形态复杂;其胶结物为断层泥,与围岩变质程度不协调,此外,不含沉积变质砾岩角砾,包括冰川角砾以及砾岩中的石英颗粒普遍具波状消光及细粒化现象等特征,这些均说明该砾岩为原地破碎胶结形成的构造角砾岩。 相似文献
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陕西洛南陶湾群三岔口组砾岩研究 总被引：4，自引：0，他引：4
陶湾群三岔口组砾岩是一套分布于华北地块南缘的水下碳酸盐岩型重力流沉积，砾岩的形成同商州铁炉子栾川断裂带早期活动性质存在因果关系。通过１∶５万区调填图发现，陶湾群三岔口组砾岩从母岩区到砾岩堆积区之间无断陷作用；沉积基底基本连续；砾岩沉积组构出现有序的横向变化规律，依次为母岩区层状白云岩（α区）、具有垂向张裂隙及流动构造的始滑区白云岩（β区）、具有节状构造的滑移区白云岩（γ区）和砾岩堆积区（δ区）。陶湾群三岔口组砾岩时代厘定为早寒武世晚期至中寒武世，这也是华北地块南缘盆地环境的主形成期，砾岩是在东秦岭洋向华 相似文献
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《地质科技情报》2017,(4)
三好砾岩出露于北京周口店地区太平山北坡,不整合覆盖于中奥陶统马家沟组之上,以分选好、磨圆好、胶结好为特征。研究表明:三好砾岩是一套二次改造的滨岸砾岩,代表了晚石炭世海侵过程中的底砾岩。来自于砾岩和其夹层中砂岩层的碎屑岩浆锆石年龄均集中在330~300 Ma之间,峰值年龄为约310 Ma,结合区域地层展布情况与华北北缘的构造热事件记录认为,它是晚石炭世至早二叠世沉积,具备准同生沉积特征。借助上述U-Pb年代学数据,结合碎屑组分特征、古流向分析及同期华北北缘岩相古地理分布特征表明,三好砾岩的物源区为内蒙古隆起。以三好砾岩为代表的上石炭统底砾岩反映了内蒙古隆起迅速隆升、剥蚀、搬运和沉积的过程,这套砾岩亦可以作为当时盆山边界的标识物。三好砾岩中高含量的晚石炭世岩浆锆石暗示了内蒙古隆起初始隆升的时限应在330~300 Ma之间。 相似文献
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Emily Keeble David I. Whiteside Michael J. Benton 《Proceedings of the Geologists' Association. Geologists' Association》2018,129(2):99-119
Pant-y-ffynnon Quarry in South Wales yielded a rich cache of fossils in the early 1950s, including articulated specimens of new species (the small sauropodomorph dinosaur Pantydraco caducus and the crocodylomorph Terrestrisuchus gracilis), but no substantial study of the wider fauna of the Pant-y-ffynnon fissure systems has been published. Here, our overview of existing specimens, a few described but mostly undescribed, as well as freshly processed material, provides a comprehensive picture of the Pant-y-ffynnon palaeo-island of the Late Triassic. This was an island with a relatively impoverished fauna dominated by small clevosaurs (rhynchocephalians), including a new species, Clevosaurus cambrica, described here from a partially articulated specimen and isolated bones. The new species has a dental morphology that is intermediate between the Late Triassic Clevosaurus hudsoni, from Cromhall Quarry to the east, and the younger C. convallis from Pant Quarry to the west, suggesting adaptive radiation of clevosaurs in the palaeo-archipelago. The larger reptiles on the palaeo-island do not exceed 1.5?m in length, including a small carnivorous crocodylomorph, Terrestrisuchus, and a possible example of insular dwarfism in the basal dinosaur Pantydraco. 相似文献
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Gilles Serge Odin 《Comptes Rendus Geoscience》2002,334(6):409-414
Lithostratigraphy, physicochemical stratigraphy, biostratigraphy, and geochronology of the 77–70 Ma old series bracketing the Campanian–Maastrichtian boundary have been investigated by 70 experts. For the first time, direct relationships between macro- and microfossils have been established, as well as direct and indirect relationships between chemo-physical and biostratigraphical tools. A combination of criteria for selecting the boundary level, duration estimates, uncertainties on durations and on the location of biohorizons have been considered; new chronostratigraphic units are proposed. The geological site at Tercis is accepted by the Commission on Stratigraphy as the international reference for the stratigraphy of the studied interval. To cite this article: G.S. Odin, C. R. Geoscience 334 (2002) 409–414. 相似文献
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The effect of water on accessory phase solubility in subaluminous and peralkaline granitic melts 总被引：4，自引：0，他引：4
The solubilities of columbite, tantalite, wolframite, rutile, zircon and hafnon were determined as a function of the water contents in peralkaline and subaluminous granite melts. All experiments were conducted at 1035 °C and 2 kbar and the water contents of the melts ranged from nominally dry to approximately 6 wt.% H2O. Accessory phase solubilities are not affected by the water content of the peralkaline melt. By contrast, solubilities are affected by the water content of the subaluminous melt, where the solubilities of all the accessory phases examined increase with the water content of the melt, up to 2 wt.% H2O. At higher water contents, solubilities are nearly constant. It can be concluded that water is not an important control of accessory phase solubility, although the water content will affect diffusivities of components in the melt, thus whether or not accessory phases will be present as restite material. The solubility behaviour in the subaluminous and peralkaline melts supports previous spectroscopic studies, which have observed differences in the coordination of high field strength elements in dry vs. wet subaluminous granitic glasses, but not for peralkaline granitic glasses. Lastly, the fact that wolframite solubility increases with increasing water content in the subaluminous melt suggests that tungsten dissolved as a hexavalent species. 相似文献
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Emmanuel Skourtsos Daniel Vachard Alexandra Zambetakis-Lekkas Rossana Martini Louisette Zaninetti 《Comptes Rendus Geoscience》2002,334(12):925-931
Some olistolites reworked in a Tertiary flysch of Mount Parnon (Peloponnesus, Greece) exhibit a Late Permian assemblage, dominated by Paradunbarula (Shindella) shindensis, Hemigordiopsis cf. luquensis and Colaniella aff. minima. This association corresponds to the Late Wuchiapingian (=Late Dzhulfian), a substage whose algae and foraminifera are generally little known. Contemporaneous limestones crop out in the middle part of the Episkopi Formation in Hydra, but they are rather commonly reworked in Mesozoic and Cainozoic sequences. The palaeobiogeographical affinities shared by the foraminiferal markers of Greece, southeastern Pamir, and southern China, are very strong (up to the specific level), and are congruent with the Pangea B reconstructions. To cite this article: E. Skourtsos et al., C. R. Geoscience 334 (2002) 925–931. 相似文献
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正20141596 Liu Yunhuan(School of Earth Sciences and Resources,Chang’an University,Xi’an 710054,China);Shao Tiequan Early Cambrian Quadrapyrgites Fossils of Xixiang Boita in Southern Shaanxi Province(Journal of Earth Sciences and Environment,ISSN1672-6561,CN61-1423/P,35(3),2013,p.39-43,3 illus.,20 refs.) 相似文献
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正20141719 Chen Zhijun(State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences,Wuhan 430074,China);Chen Jianguo Automated Batch Mapping Solution for Serial Maps:A Case Study of Exploration Geochemistry Maps(Journal of Geology,ISSN1674-3636,CN32-1796/P,37(3),2013,p.456-464,2 illus.,2 tables,10 refs.) 相似文献
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正20140962 Chen Fenning(Xi’an Institute of Geology and Mineral Resources,Xi’an710054,China);Chen Ruiming Late Miocene-Early Pleistocene Ostracoda Fauna of Gyirong Basin,Southern Tibet(Acta Geologica Sinica,ISSN0001-5717,CN11-1951/P,87(6),2013,p.872-886,6illus.,56refs.) 相似文献
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正1.IGNEOUS PETROLOGY20142008Cai Jinhui(Wuhan Center,China Geological Survey,Wuhan 430205,China);Liu Wei Zircon U-Pb Geochronology and Mineralization Significance of Granodiorites from Fuzichong Pb-Zn Deposit,Guangxi,South China(Geology and Mineral Resources of South China,ISSN1007-3701,CN42-1417/P,29(4),2013,p.271-281,7illus., 相似文献
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正20141205Cheng Weiming(State Key Laboratory of Resources and Environmental Information System,Institute of Geographic Sciences and Natural Resources Research,CAS,Beijing 100101,China);Xia Yao Regional Hazard Assessment of Disaster Environment for Debris Flows:Taking Jundu Mountain,Beijing as an 相似文献