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1.
晚震旦世至早寒武世扬子地台北缘碳同位素研究 总被引：5，自引：0，他引：5
震旦-寒武交变期是地史上一个重大转折期,亦是一个具有特殊意义的过渡时期。运用碳同位素地球化学方法,探讨扬子地台北缘四川南江地区晚震旦世-早寒武世交变期,碳同位素地球化学异常与环境变化和生物演化的相互联系。南江剖面沉积岩有机碳同位素组成在-35．8‰～-30．1‰间变化;碳酸盐碳同位素组成从-3．5‰～ 0．5‰。在灯影组顶部、牛蹄塘组下部和上部,变化的碳、硫同位素组成和不同的黄铁矿与有机碳含量反映了有机碳埋藏量和环境的变化。下寒武统富有机碳和黄铁矿的黑色页岩沉积,暗示了早寒武世早期缺氧环境的存在。 相似文献
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在扬子地台通过对晚震旦世-古生代地层中许多硅岩层的主元素和微量元素含量及组合关系的研究,总结了硅岩的地球化学特征,进而讨论硅质的来源和硅岩形成的地质背景及其有利的地球化学条件。 相似文献
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湖北徐家山锑矿床特征、稳定同位素组成及其成矿机理的初步探讨 总被引：4，自引：0，他引：4
徐家山锑矿床产在上震旦统陡山沱组和灯影组海相碳酸盐岩地层中。矿石中含有硒。矿床成因类型属于沉积-渗流热水成矿溶液改造富集型层控锑矿床。本文在论述矿床地质特征、成矿阶段的划分、矿物包裹体特征及稳定同位素地球化学等研究成果的基础上,探讨了该矿床的成矿机理。 相似文献
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燕山地区震旦亚界研究历史悠久。早在1934年,高振西教授对蓟县震旦地层进行了研究。解放后,我国地质工作者从岩石学、古生物学、同位素地质学等角度,对该区震旦亚界进行了详细探讨。近年,国外不少地质学家亦先后来我国参观震旦亚界地层。为了提高对晚前寒武纪地层的 相似文献
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贵州瓮安陡山沱组剖面碳同位素生物地球化学研究 总被引：4，自引：0，他引：4
在对扬子地台贵州瓮安陡山沱组剖面干酪根碳同住素组成进行分析后发现其变化显示了一定的规律性。碳同住素规律变化反映了最初的沉积信息,特别是有机质埋藏量的变化。获得的陡山沱期沉积岩中碳同位素组成研究结果初步反映了震旦一寒武交变期沉积环境的面貌;碳同位素组成变化规律可以用于反映扬子地台沉积层序和世界同期地层全球碳循环的对比和参考。为扬子区陡山沱期环境变化和生物演化提供了证据。δ^13Cker值在-32．3‰和-24．5‰(PDB)间漂移与δ^13Ccarb值在-4．9‰和3．6‰(PDB)间的变化,反映了当时海水的碳同位素组成。无机和有机碳同位素组成之差的△δorg-carb值沿剖面不断变化,是由于沉积有机质中有促进发酵功能的细菌数量比例变化所致。 相似文献
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广东南雄盆地白垩系—古近系界线 总被引：3，自引：0，他引：3
在过去的30年中有数支考察队在广东南雄盆地进行了白垩纪和古近纪地层多学科的系统研究。本文综合了南雄盆地近年的岩石地层学、磁性地层学、地球化学、古生物学方面的研究成果和湖北新洲盆地时代相当于浓山组的地层中得到的同位素年龄,认为上湖组时代大体上与Danian期相当,或相当于北美哺乳动物分期Puercan和Torrejo-nian期,其底界接近于白垩系—古近系界线。 相似文献
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本文应用统计分析方法,从化学地层角度探讨苏皖北部上元古界的地质特征、各地层单元及地质界线附近地球化学信息的变化,以及元素在时间域中演化的波浪式特征。同时提出在原青白口及震旦化学阶段内部划分出三个次级的化学亚阶段。 相似文献
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锶同位素地层学是稳定同位素地球化学方法在地层学中的重要应用。本文基于87Sr/86Sr在地球历史中的特殊演化规律,以二叠系乐平统为例介绍了锶同位素地层学的研究方法、技术路线以及在地层学研究中需要关注的问题,特别是详细介绍了样品采集、化学预处理、分析测试仪器设备的选择,以及后期数据处理等方法和这些方法在使用中存在的问题、解决方案和简要理论依据。作为重要的化学地层学方法之一,锶同位素地层学可以为地层的划分和对比,及相关的古环境、古构造、古海洋等的研究提供新的依据和研究手段,而且对缺乏生物地层资料的剖面的断代、划分和对比提供了一种可靠的方法。 相似文献
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本文利用硅岩中Si、O、C和Rb-Sr多种同位素的组成特点及分布趋势作为重要的地球化学标志，来判别扬子地台晚震旦世以来硅岩的成因、物质来源和形成环境。 相似文献
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贵州乐康P/T界线无机碳同位素特征及其意义 总被引：2，自引：0，他引：2
贵州乐康深水海槽相中的无机碳同位素研究表明,晚二叠世由于局限环境,区域内生物贫乏,相对应的碳同位素值比同期其他剖面中碳同位素值偏低。而在长兴阶晚期,由于受区域内火山作用的影响,在剖面界线之下发育另一个碳同位素负异常,之后碳同位素有所回升,直至界线附近降低为最低值。早三叠世由于绝灭之后的生物复苏缓慢,无机碳同位素表现为低正值。碳同位素特征显示,碳同位素的变化受到了生物和环境等多种因素的综合控制。 相似文献
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Hai Thanh Tran Bat Van Dang Chi Kim Ngo Que Dinh Hoang Quyen Minh Nguyen 《Environmental Earth Sciences》2013,70(2):511-520
Karstified assemblages occur widely in, and distinctively shape, the geological landscape of the northeastern part of Vietnam. These carbonate rocks were deposited during three major periods of basinal evolution including: (1) Late Cambrian, (2) Early Devonian to Early Carboniferous, and (3) Carboniferous to Earliest Triassic. These sedimentary units contain primary sedimentary structures and have undergone numerous post-depositional geological processes including multiple deformational events, which can be regionally correlated. Several thrusting events and associated folding have led to significant thickening of the carbonate units. The subsequent post-thrusting cross-folding events, followed by several phases of brittle faulting and fracturing further modified the spatial geometry and outcrop of these rocks. The combination and interaction of the primary structures with those formed during the long-lived and complicated deformational history is an important controlling factor in local and regional hydrogeological systems in the region. The geological structures now recorded in the carbonate units ultimately govern the formation of the unique modern surface and sub-surface geomorphology of the karstic terrains in northeastern Vietnam. These structures should be further investigated in the context of water resource assessment and natural hazard prediction and mitigation. 相似文献
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Leonard Robert Gardner 《Chemical Geology》1984,46(1):55-73
Stable carbon and oxygen isotope measurements have been obtained from ten calcareous soil profiles developed on noncalcareous parent materials in Nevada and New Mexico. Despite the number of variables that can affect the isotopic composition of soil carbonate, most of these profiles show remarkably little variation in δ 13C and δ 18O with depth. This tendency towards uniformity is attributed to the fact that pedogenic carbonate forms by the incremental accumulation of a large number of small aliquots of CaCO3. As the number of aliquots of CaCO3 increases, the composition of their sum, which is the calcareous horizon itself, tends to converge to the long-term average of the individual aliquots. A mathematical model is presented to show how the time required for convergence is affected by the amplitude and period of aliquot variation and the extent of dissolution and reprecipitation of previously deposited carbonate. Calculations further indicate that in some cases the variation in δ 18O of soil carbonates may be moderated by the opposing effects of temperature change on the H2OCaCO3 fractionation factor and on the extent of evapotranspiration.The data of this study indicate that soil carbonates from sites within a homogeneous climatic region show relatively little site-to-site variation in δ 18O as compared to geographical variation in δ 13C. This suggests that the δ 18O of soil carbonates is primarily controlled by broad climatic factors (rainfall composition and temperature) whereas site factors (e.g., soil CO2) have a strong effect on δ 13C. In Nevada and New Mexico the δ 18O of Pleistocene calcareous profiles is 2.0–4.0‰ lighter than that of nearby Holocene soil carbonate, suggesting that old well-developed profiles may have formed dominantly under cooler pluvial conditions. 相似文献
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The evolution of carbonate groundwaters may occur in a so-called open or closed system or under conditions between the extremes. In order to distinguish between the cases the chemistry of the water and the carbon isotope composition of the dissolved carbonate, the carbonate rock and the soil CO2 of the recharge area must be known. Model calculations based on measurements of the above parameters show that ground-waters in the “Schwäbische Alb”, Federal Republic of Germany, are evolved essentially under closed-system conditions. The average measured carbon isotope composition of the water is δ 13C = ?13.7%0 vs. calculated values of δ 13C = ?13.5%0 and δ 13C = ?18.5%0 assuming a closed and an open system, respectively. In model calculations for closed-system conditions the origin of sulfate ions has to be considered. 相似文献
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Qiao Xiufu Song Tianrui Gao Linzhi Peng Yang Li Haibing Gao Mai Song Biao Zhang Qiaoda 《《地质学报》英文版》1994,7(3):243-265
Abstract On the basis of the records of strong seismic events taking place in soft carbonate sediments, a new seismic sequence system of vibrational liquefaction is established, which consists of a series of units, such as escaped structure of micrite veins and liquefied deformation formed in the period of seismic liquefaction, land subsidence structure after liquefaction, tsunamic hummocky and turbidite produced by seismic events, This sequence is a generalization and summation of field observation in vast areas, which shows the whole process of a strong seismic event and provides an unified theoretical explanation. The pattern of the seismic sequence by vibrational liquefaction provides one of correlation standards for geologists in the field to discriminate events in carbonate sequences. Based on the pattern of seismic sequence, the authors first advance a new conception of the Palaeo - Tanlu (Tancheng - Lujiang) Zone and discuss primarily its geological significations. 相似文献
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Seismic Sequence in Carbonate Rocks By Vibrational Liquefaction 总被引：16，自引：0，他引：16
Qiao Xiufu Song Tianrui Gao Linzhi Peng Yang Li Haibing Gao Mai Song Biao Zhang QiaodaInstitute of Geology Chinese Academy of Geological Sciences Beijing 《《地质学报》英文版》1994,68(3)
On the basis of the records of strong seismic events taking place in soft carbonate sediments, a new seismic sequence system of vibrational liquefaction is established, which consists of a series of units, such as escaped structure of micrite veins and liquefied deformation formed in the period of seismic liquefaction, land subsidence structure after liquefaction, tsunamic hummocky and turbidite produced by seismic events, This sequence is a generalization and summation of field observation in vast areas, which shows the whole process of a strong seismic event and provides an unified theoretical explanation. The pattern of the seismic sequence by vibrational liquefaction provides one of correlation standards for geologists in the field to discriminate events in carbonate sequences. Based on the pattern of seismic sequence, the authors first advance a new conception of the Palaeo-Tanlu (Tancheng-Lujiang) Zone and discuss primarily its geological significations. 相似文献
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南海新生代碳酸盐台地淹没事件记录的海底扩张 总被引：12，自引：0，他引：12
本文通过对南海4个碳酸盐台地及其淹没事件的分析来阐明南海海底扩张的演化史.南海碳酸盐台地出现在最大海底扩张期,淹没事件出现在海底扩张和地壳下降速率进一步加快时期,因而它记录了海底扩张的阶段性和不均一性.南海共经历了早中新世晚期(距今17±0.5 Ma)、晚中新世早期(距今10.0～8.2 Ma)和上新世早期(距今3.4～3.0 Ma)等3次大的淹没事件,表明南海经历了3次大的海底扩张,短暂淹没事件是与海底扩张有关的各种地质事件的反映. 相似文献
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Microfacies of Deep-water Deposits and Forming Models of the Chinese Continental Scientific Drilling-SKII 总被引：3，自引：0，他引：3 
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下载免费PDF全文 Extensive transgression of lake water occurred during the Cretaceous Qingshankou Stage and the Nengjiang Stage in the Songliao basin, forming widespread deep-water deposits. Eleven types of microfacies of deep-water deposits have been recognized in the continuous core rocks from the SKII, including mudstone of still water, marlite, dolostone, oil shale, volcanic ashes, turbidite, slump sediment, tempestite, seismite, ostracoda limestone and sparry carbonate, which are divided into two types: microfacies generated due to gradually changing environments (I) and microfacies generated due to geological events (II). Type I is composed of some special fine grain sediments such as marlite, dolomite stone and oil shale as well as mudstone and Type II is composed of some sediments related to geological events, such as volcanic ashes, turbiditie, slump sediment, tempestite, seismite, ostracoda limestone. The formation of sparry carbonate may be controlled by factors related to both environments and events. Generally, mudstone sediments of still water can be regarded as background sediments, and the rest sediments are all event sediments, which have unique forming models, which may reflect controlling effects of climatics and tectonics. 相似文献
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湘西罗依溪剖面包含有被国际地层委员会寒武系分会表决通过的、确定全球寒武系第三统第七阶底界的球接子三叶虫Lejopygelaevigata的首现点位,是全球寒武系第三统第七阶GSSP的候选剖面。野外按0.25—0.5m的样品间距,对该点位附近的碳酸盐岩采取了264件碳、氧同位素样品,分析结果表明全球寒武系第三统Drumian阶上部δ13C值呈恒幅波状演化、波动范围较小,δ18O波动强烈、幅度较大;而第七阶下部δ13C值跳跃强烈、幅度较大,总体表现为高值,δ18O值波动减弱、趋向低值;全球寒武系第三统第七阶底部的候选GSSP正好处于δ13C值由恒幅波动向剧烈跳跃的转折处。第七阶早期δ13C值、δ18O值及海平面三者之间存在较好的耦合关系,表现为海平面上升到最高位置、δ13C值较高、δ18O值较低,造成耦合的原因可能为全球气候变暖,大量淡水流向海洋、海域扩大,初始生产率提高,较多12C为生物所摄取,导致海水中13C的浓度相对升高,沉积的碳酸盐岩具有较高的δ13C值。同时,由于最大海泛期洋流活动频繁,对江南斜坡带沉积作用有一定影响,致使碳酸盐岩沉积物的碳、氧同位素组成变化较大。 相似文献