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1.
富勒烯（Fullerene）为除金刚石和石墨外碳元素的第三种同素异形体，自Kroto等1985年发现以来，对富勒烯的研究一直是世界性的热点话题，并在多个方面取得重要进展。它具有稳定的封闭笼状结构，被认为在星际空间广泛存在。富勒烯的形成条件特殊，普通的地球环境和地质过程不利于富勒烯的生成。1992年天然富勒烯在俄罗斯前寒武纪地层桑加岩（Shungite）中被发现，引起了人们对天然富勒烯研究的兴趣。随着富勒烯在陨石和撞击构造中的发现，人们更加关注事件地层中富勒烯存在的可能性以及它们的可能来源。二叠纪—三叠纪（P-T）之交发生了地质历史上规模最大的生物灭绝事件，因此，学者十分关注P-T界线地层中是否能检测到天然富勒烯的的存在。文章回顾了富勒烯在陨石、撞击构造、K-T界线地层和P T界线地层的研究进展，并重点对P-T界线富勒烯的存在问题进行讨论，指出从样品采集到样品测试，每一个环节都可能影响富勒烯的检出。P-T界线地层富勒烯可能源于陨石撞击、天然大火等极端地质事件，而包裹在富勒烯碳笼的稀有气体的同位素组成提供了进一步区分的重要证据。事件地层中普遍存在富勒烯，表明天然富勒烯可以作为地层中发生过重大灾变事件的重要的地球化学指标，而具有异常稀有气体同位素组成的富勒烯则是地外撞击事件的最直接证据。 相似文献
2.
运用化学分离、液相色谱和基体辅助飞行时间质谱等综合方法 ,确定了煤山剖面的富勒烯不仅存在于二叠 -三叠系(P/T)事件界线白粘土中 ,更相对富集在此白粘土底部的微层中 ,相反 ,在 P/T界线附近的其他地层包括其他粘土层中均未检测到富勒烯。富勒烯在白粘土底部微层中相对富集的事实与最近获得的碳酸盐碳同位素最大负异常和生物消失最突然和最严重的位置均指向煤山剖面该白粘土底部与下层灰岩交界处的现象一致 ,表明富勒烯与 P/T灾变事件相关规律值得进一步深入研究。本文结果同时证实了曾多有争议的 Becker等人关于煤山剖面 P/T事件界线… 相似文献
3.
从P∈—∈,P—T等地层界线上的特征岩石、古生物大规模灭绝和Ir及ξ~(13)C的异常等研究表明,与K—R界线一样,在这些界线上也可能存在有地外灾变事件。同时文中提出了界线灾变事件、界线灾变期、界线灾变环境、界线层、界线粘土层、梅树村地质事件等与研究事件地层学有关的一系列新概念。 相似文献
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选择川北江油滚柴坡和广元上寺、杨家湾二叠系-三叠系界线剖面为研究对象,利用中子活化法分析了粘土岩样品中稀土元素的组成.通过对稀土元素丰度、标准配分模式和特征参数的比较研究,探讨了稀土元素地球化学与自然环境突变的关系.结果表明,各剖面的?Eu、?Ce、∑LREE/∑HREE-∑REE、Eu/∑REE-∑LREE/∑HREE、球粒陨石标准化曲线图解和La-Th-Sc三元图解一致反映了界线事件的存在及界线时期稀土元素的地球化学特征与环境突变的关系.同时,通过对3条剖面稀土元素地球化学特征与标准剖面的对比研究,认为P/T(二叠系/三叠系)界线事件时期环境不仅受中酸性火山作用的影响,还可能受(碱性)基性-超基性或地外溅射物的影响.研究结果为从元素地球化学的角度探讨这一重要地质时期的灾变事件提供了新的资料. 相似文献
7.
本文译自《东特提斯二叠—三叠纪(P/T)事件》(英文本)第一章,包括六方面内容:(1)生物地层学,利用腕足类、菊石类、牙形石和植物,建立P/T界线间隔的生物地层表;(2)地球化学研究,讨论目前可用资料,绘出P/T界线间隔的δ~(13)C和δ~(16)O剖面;(3)古地磁研究,借以决定同一界线间隔的划分;(4)火山作用,大多数作者用火山成因解释P/T界线间隔;(5)生物更替原因,包括主要的海侵,广泛的火山作用和火流星的溅射;(6)多方面证据说明P/T界线最好划在Changxingensis带和Isarcica带之间。 相似文献
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撞击地层学及其研究进展 总被引：2，自引：0，他引：2
地质历史中的地外物体撞击地球事件可在撞击点、近源区和远源区分别形成撞击坑熔融岩体、近源溅射岩席及海啸沉积和远源溅射层等一系列撞击地层层序。撞击地层有其独特的物理学和化学特征,与正常沉积作用、火山喷发和板块碰撞等成因的地层显然有别。通过对撞击地层层序的时空变化、所包含的撞击成因矿物、撞击微球粒和微玻璃陨石以及古生物和地球化学异常等的研究,可以了解撞击事件的发生频率、幅度和撞击天体的性质等,也为探索生物和地球环境的灾难性变化及其起因提供了新的思路。 相似文献
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黔北大方地区二叠纪及三叠纪地层发育,在二叠系—三叠系界线处发现12~14cm厚的界线粘土,在界线粘土层之上还发现3~4层5~18cm厚的火山事件粘土层。二叠系—三叠系界线粘土、事件粘土及松子坎段底部火山事件粘土岩(绿豆岩)均具有高的K_2O和MgO含量;二叠系—三叠系界线粘土的稀土元素特征与关岭组松子坎段底部绿豆岩相似,与沙堡湾段事件粘土岩的稀土元素特征也十分相似,Eu异常较明显,说明界线粘土及事件粘土成因均与火山活动有密切关系。界线粘土比事件粘土具更明显的Eu异常,部分界线粘土还具有Ce异常。二叠系—三叠界线粘土、事件粘土及关岭组绿豆岩的源区均属于活动大陆边缘的长英质火山岩区,为酸性的长英质火山岩喷发(火山灰)沉积的产物,而沙堡湾段及九级滩段正常沉积泥岩的源区属于被动大陆边缘的长石砂岩岩区。界线粘土中,大部分微量元素与事件粘土及关岭组绿豆岩中对应微量元素的含量相近,但其中的Th、Y、Nb、Cd、Ga、In、Ta明显高于与火山活动有关的事件粘土及绿豆岩,推测事件粘土与少量宇宙事件外来物质的加入有关。 相似文献
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黔西威宁岔河陆相二叠系-三叠系界线粘土岩研究--基于X射线衍射、扫描电镜分析 总被引：3，自引：0，他引：3
利用X射线衍射、扫描电镜等分析方法,对黔西威宁岔河陆相剖面二叠系-三叠系界线附近的粘土岩进行了研究.在界线粘土岩中,粘土矿物组合为伊-蒙混层矿物 蒙脱石 绿泥石;碎屑物质中有六方双锥石英和锆石,无球粒;多种化学成分在界线粘土岩中出现了异常.据此得出岔河剖面的二叠系-三叠系事件地层界线确定在第66f层比较合适;第66f和68a这两层粘土岩为此剖面的界线粘土岩;自第66f层底部至第68a层顶部这一段地层为二叠系-三叠系的界线层(组);界线粘土岩的成因可能是由于火山喷发、火山灰降落伴随正常沉积物沉积形成的. 相似文献
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Determination of Fullerenes (C_(60)/C_(70)) from the Permian-Triassic Boundary in the Meishan Section of South China 总被引：1，自引：0，他引：1
LI Yanfang LIANG Handong YIN Hongfu SUN Jing CAI Hou''an RAO Zhu RAN Fanlin China University of Mining Technology Beijing Key Laboratory of Coal Resources Ministry of Education Beijing China University of Geosciences Wuhan Hubei 《《地质学报》英文版》2005,79(1):11-15
Fullerenes (C60/C70), clays and rocks near the Permian-Triassic (P/T) boundary in the Meishan section of South China are explored by means of comprehensive analytical techniques, including ultrasonic extraction with column purification, high-performance liquid chromatography (HPLC) and matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI TOF MS). The study confirms the existence of fullerenes toward the P/T event boundary and their absence in clays and limestones beyond the boundary. In particular, the white clay, known as the event boundary, contains fullerenes of 0.33 ppb, while the red material, as the first lamina fill of goethite and gypsum on the base of the white clay, contains fullerenes of 1.23 ppb, and the last lamina of 2.50 ppb. Significantly, distinct enrichment of fullerenes is coincident with the disappearance of fossil records of marine species (94%) just at the base of the white clay,implying that geological fullerenes would be one of temporal remnants led by the P/T catastrophic event. This work strongly supports that fullerenes would be one of significant records of the P/T catastrophic event but their origin remains to be studied further. 相似文献
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Gilberto A. Albertão Eduardo A.M. Koutsoukos Marília P.S. Regali Moses Attrep Jr Paulo P. Martins Jr 《地学学报》1994,6(4):366-375
A preliminary integrated study of a Cretaceous-Tertiary (K/T) boundary section in Pernambuco, northeastern Brazil, provides evidence for an extraterrestrial bolide impact in the earliest Danian. A non-graded, nodular carbonate mudstone/wackestone bed is interpreted as a slump or a mud Flow deposit, induced by a tsunami event or by a gravity mass movement during a sea-level lowstand, the former possibly generated by the K/T boundary Yucatán impact. This bed overlies marlstones deposited in an upper bathyal environment and marks the top of the Cretaceous. Nearly all known latest Maastrichtian planktonic foraminifera are recovered from the Cretaceous strata. Iridium shows a marked peak in a thin hemipelagic claystone layer, about 75 cm above the K/T boundary, deposited in a middle to deep neritic environment. The claystone overlies alternating beds of finegrained limestones and marlstones and a 50 cm-thick graded bioclastic packstone, which rests upon a marly limestone breccia of the lowermost Danian. Abundant reworked Cretaceous and rare lowermost Danian microfossils (e.g. E. edita, E. eobulloides, E. fringa, G. irregularis, P. eugubina, P. cf. pseudobulloides, W. claytonensis and W. hornerstownensis ) have been recovered from these strata. These lowermost Danian beds record the sudden appearance of abundant shock-metamorphosed quartz grains, with several sets of intersecting deformation lamellae and microtektite-like microspherules. This suggests that these deposits were formed by an additional tsunami caused by a second impact event in the earliest Danian, near or at the boundary between the Palaeocene P α and P 1a foraminiferal zones. Impact-derived material has not been found in the uppermost Cretaceous beds. 相似文献
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GEOLOGICAL EVENT ACROSS THE BOUNDARY OF THE LATEST PALEOCENE TO EARLIEST EOCENE IN TINGRI, SOUTHERN TIBET1 DickensGR ,CastilloMM ,WalkerJCG .AblastofgasinthelatestPaleocene :Simulatingfirst ordereffectsofmassivedissociationofoceanicmethanehydrate[J].Geology ,1997,2 5 (3) :2 5 9～ 2 6 2 .
2 GibsonTG ,BybellLM .Paleocene/EoceneboundarystrataandeventsintheU .S .AtlanticCoastalPlains[J].JournalofVertebratePaleontology ,1993,13(3suppl.) :37.
… 相似文献
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《Earth》2004,64(1-2):119-155
In several recent papers, M.-P. Aubry et al. have argued that “Hedbergian” principles of chronostratigraphy are being violated by the International Commission on Stratigraphy (ICS) when selecting Global Stratotype Sections and Points (GSSPs) for the formal divisions of the geological time scale. The current debate over the definition of the Paleocene/Eocene (P/E) boundary has been a major focus of their arguments. Unfortunately, Aubry et al. have obscured matters by misusing the term “unit stratotype,” and by equivocally using the term “stage” for the very different concepts of “synthem” and “global chronostratigraphic stage.” The P/E boundary option most repugnant to Aubry et al. (Carbon Isotope Excursion (CIE)=P/E=Thanetian/Ypresian boundary) is perfectly compatible with H.D. Hedberg's views. In contrast, another option preferred by Aubry et al. (recognition of new ∼1 m.y. duration age/stage between Thanetian and Ypresian) is inconsistent with Hedberg's views. Additional problems with the P/E boundary arguments of Aubry et al. include the fact that a “Ypresian unit stratotype” does not exist, the fact that the base of the Ypresian synthem is not immutable, and the fact that the nannofossil Tribrachiatus digitalis is of dubious relevance to the boundary debate.As for chronostratigraphy in general, Aubry et al. have misrepresented Hedberg's views by: (1) falsely claiming that the content of a stage is what determines its boundaries; (2) misunderstanding the general concept of the boundary stratotype; (3) distorting the “base defines boundary” principle; (4) falsely claiming that traditional (pre-GSSP) chronostratigraphic boundaries cannot be changed; (5) falsely implying that traditional stage unit stratotype boundaries can be adjusted by no more than 300,000 years when defining formal age/stage boundaries with GSSPs; (6) falsely claiming that the definition of a geochronologic/chronostratigraphic boundary should precede its correlation; (7) claiming that traditional unconformable “stage” boundaries may be suitable horizons for GSSPs; (8) distorting the meaning of “arbitrariness” in regard to the definition of geochronologic/chronostratigraphic boundaries; and (9) claiming that GSSPs are inherently unstable in that they are subject to redefinition whenever a more powerful element of correlation is discovered. If taken seriously, the unit stratotype-sanctifying chronostratigraphic philosophy of Aubry et al. would require the creation of perhaps dozens of new Phanerozoic ages/stages of relatively very short duration wherever there was a significant gap between two successive historical stage unit stratotypes. For all of these reasons, the arguments of Aubry et al. have no merit. 相似文献
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撞击事件诱发核反应热力学过程及其在事件地质学研究中的意义 总被引：1，自引：0，他引：1
从大规模撞击事件的基本动力学和热力学公式推导出发，讨论了白垩纪－第三纪界线（Ｋ／Ｔ界线）事件能量随时间的释放过程，并对发生热核聚变反应的条件进行了分析。最后，还对其可能的事件地质学意义进行了讨论． 相似文献
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K/T boundary geochemical anomalies have been used previously to support the impact event at the end of the Cretaceous. However, impact models and assessment of the extraterrestrial contribution to the boundary sediments should also consider the diagenetic alteration of the impact signatures. Mineralogical and geochemical studies centring on redox proxies reveal differences in trace-element concentrations at Agost and Caravaca (SE Spain), two of the most complete K/T boundary sections. These differences probably derive from variations in the diagenetic evolution of the ejecta layer. Several redox proxies, such as extensive pyrite formation, high authigenic uranium concentration and positive Eu anomalies, indicate very strong reducing conditions at Agost. Positive Eu anomalies are extremely unusual in sediments, and in this case are interpreted to indicate a highly reducing environment. In such conditions, certain trace elements such as Ir, may have been remobilized, thereby masking the original signature of the impact. 相似文献
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KT Boundary Chromites Determined to be Terrestrial: Cr Isotopic Evidence for Excavation and Ejection of Mafic/Ultramafic Rocks by the KT Boundary Impact 
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下载免费PDF全文 Evidence for a mantle and/or basaltic component in KT boundary distal ejecta is apparently inconsistent with ejection from Chicxulub Crater since it is located on~35km thick continental crust(De Paolo et al.,1983;Montanari et al.,1983;Hildebrand and Boynton,1988,1990).Evidence for mafic/ultramafic target rocks was reinforced by discovery of chromites,some with shock planar deformation features(PDF),in impact layer samples from sites in southern Colorado and eastern Wyoming(Bohor et al.,1990).However,until now it was unclear whether the chromites originated with an impactor or with terrestrial target rocks.To this end,high-precision 54Cr/52Cr isotope ratios were measured on KT boundary chromites along with known terrestrial chromites.We find a terrestrial 54Cr/52Cr ratio in KT boundary chromites from impact layer samples collected at the above sites over the last several years(Fig.1).Ejected terrestrial chromites suggest the impact sampled terrestrial mafic and/or ultramafic target rocks not known to exist in the Chicxulub target area. 相似文献
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中国南方二叠-三叠系界线及其附近粘土层稀土元素地球化学研究 总被引：5，自引：0，他引：5
本文对广泛发育于中国南方,连续的二叠-三叠系海相界线及其附近粘土层(蒙脱石—伊利石粘土岩)进行了稀土元素地豫化学的研究。查明了REE分布特征;REE沿粘土层垂向上的变化,比较了界线粘土与非界线粘土在REE分布上的差异。讨论了界线粘土的成因,根据稀土模式所作的综合分析,提出了由中酸性山火山岩和代表冲击溅射产物的上部地壳物质组合的混合新模式。 相似文献
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The investigation of eight Cretaceous-Tertiary (K/T) sections in Mexico, based on major and trace element, platinum group element (PGE), stable isotope, and multivariate statistical analysis, reveals a complex depositional history across the Chicxulub and K/T boundary events. At the biostratigraphically determined K/T boundary, a minor but significant Ir-dominated PGE anomaly (0.2-0.8 ng/g) is present in most sections. This Ir anomaly originated from an impact event and is always stratigraphically and geochemically decoupled from the underlying spherule-rich ejecta deposit related to the Chicxulub event. In all sections examined, one to three glass spherule ejecta layers and one or two chondrite-dominated PGE anomalies are separated by a bioturbated siliciclastic deposit and/or hemipelagic marl, which indicates the occurrence of at least two impact events separated by a considerable amount of time. In addition, bentonite layers and Pt and Pd-dominated PGE anomalies below and above the K/T boundary indicate volcanic activity. Above the K/T boundary, reduced bioproductivity is documented by a decrease in the biogenically bound fraction of nutrients and fluctuating ratios of immobile elements (e.g., Ti/Zr). Variations in detrital elements reflect changes in the depositional environment. Carbon and oxygen isotope and trace element distribution patterns indicate a gradually changing climate during the latest Maastrichtian, an abrupt change at the K/T boundary, and a slight recovery during the lowermost Paleocene. 相似文献