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51.
贵州盘县峨眉山玄武岩系顶部凝灰岩LA-ICP-MS 锆石U-Pb年龄:对峨眉山大火成岩省与生物大规模灭绝关系的约束 总被引:7,自引:3,他引:4
在20世纪90年代,有学者认为峨眉山大火成岩省(Emeishan Large Igneous Province, ELIP)大规模火山活动与二叠-三叠系之交(Permian-Triassic Boundary, P-TB)的生物大灭绝事件在时间上有耦合关系,随后的40Ar/39Ar同位素测年结果也显示峨眉山大火成岩省是晚二叠世形成的。但是,近些年大量的SHRIMP U-Pb测年结果表明,ELIP大规模火山喷发约在~260Ma;因此有研究认为,ELIP火山活动与中二叠世瓜德卢普期末(end-Guadalupian)的生物灭绝事件在时间上联系更加紧密。至于P-T界线生物大灭绝,现在多数学者认为是,由于西伯利亚大火成岩省火山强烈活动释放大量气体和火山灰所造成环境变化引起的。最近,我们在ELIP东部的贵州盘县峨眉山玄武岩系剖面中发现顶部发育厚度达近百米的凝灰岩层,其LA-ICP-MS U-Pb法测年结果为251.0±1.0Ma,与浙江煤山剖面中二叠系-三叠系边界处黏土层或火山灰层的锆石U-Pb年龄接近。因此,峨眉山玄武岩喷发结束的时间应该在P-T边界,与西伯利亚大火成岩省的主体喷发时间一致。新的测年结果暗示了ELIP火山活动与地球历史上最大的一次生物灭绝事件(P-T边界)可能存在着成因联系。 相似文献
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LIU Hao WANG YongBiao YUAN AiHua YANG Hao SONG HaiJun & ZHANG SuXin Key Laboratory of Biogeology Environmental Geology of Ministry of Education Wuhan China State Key Laboratory of Geological Processes Mineral Resources 《中国科学:地球科学(英文版)》2010,(6)
Thirty species of 10 ostracod genera were identified from 440 fossil specimens isolated through the hot acetolysis of the rock samples collected across the Permian-Triassic boundary at Chongyang section. Twenty species of 6 genera are found to occur in the limestone of Changxing Formation, and 11 species of 7 genera above the main faunal mass extinction horizon. The os-tracod assemblages identified at the Chongyang section are obviously different from those previously reported in the contem-poraneous microb... 相似文献
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55.
桂西南柳桥地区深水相二叠系-三叠系界线剖面 总被引:9,自引:1,他引:8
桂西南柳桥地区上二叠统为厚约84m的浅灰—灰白色块状海绵蓝藻生物灰岩(生物礁),之上为浅灰绿色—暗灰色薄层状含远洋浮游生物硅质岩、含泥质硅质岩、硅质泥岩(大隆组),这套深水相的沉积岩夹有大量浅灰白色的粘土岩。上覆的三叠系罗楼组底部为黄色泥岩,夹多层灰白色粘土岩,往上渐变为灰色薄层状含大量双壳类、菊石化石的钙质泥岩、泥灰岩。柳桥地区晚二叠世末期沉积岩和中基性火山岩的特征显示其是在地壳裂解、快速沉降、相对海平面快速上升过程中迅速淹没台地边缘的生物礁而形成的深水相海盆,造成深水盆地与浅水台地并存,具有多岛洋的地理分布格局。东攀二叠系-三叠系界线剖面的露头完整,对剖面的岩石学特征、生物化石组合特征等方面的详细研究显示,该地区一直处于连续沉积的深水环境中,没有发生沉积间断,界线上下的岩石特征和生物组合特征较清楚。 相似文献
56.
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
57.
The well-known Permian Changhsingian calcisponge reef located at Panlongdong section,Xuanhan county,northeastern Sichuan Basin has attracted wide attention.Due to severe dolomitization and poor quality of the fossils,the P-T boundary in this section is difficult to determine.This study,for the first time,recognized six communities in the Upper Permian Changhsingian Changxing Formation through the Lower Triassic Induan Feixianguan Formation of the Panlongdong section.They are Bryozoan-Archaeolithoporella-calcisponge Community,Calcareous green algae-foraminifer-crinoid Community,Microgastropod-foraminifer Community,Ostracod-microgastropod-cystic microbe Community,Ostracod-small brachiopod Community,and Non-calcified cyanobacteria Community.By using community replacement and palaeoenvironmental analysis,for the first time,we set the P-T boundary of the Panlongdong section at the middle of the calcimicrobialite containing cystic microbes.The community replacement sequence in the Panlongdong section is similar to that in other contemporaneous sections in reef areas of South China,indicating universal palaeoenvironmental changes during the Permian-Triassic transition.The results show that:(1)Changhsingian calcisponge reefs in South China generally vanished before the mass extinction and may be related to the large regression in the Late Permian.(2)The Calcareous green algae-foraminifer-crinoid Community replaced reef community and continued till the mass extinction.The mass extinction was probably related to the global sea-level drop.(3)The first aftermath community was dominated by specialized microgastropods,followed by the microbes,and then by the specialized microgastropods and small brachiopods.The succession of the three communities reflected the change in environmental conditions from dysoxic to anoxic and again to dysoxic.(4)In the Early Triassic,the relict community in shallow sea had very low diversity and low abundance,and was dominated by crinoids,gastropods,and bivalves. 相似文献
58.
Li Tian JinNan Tong DongYing Sun YanLin Xiong ChengGang Wang HaiJun Song HuYue Song YunFei Huang 《中国科学:地球科学(英文版)》2014,57(9):2195-2207
A Permian-Triassic (P-Tr) boundary section of continuous carbonate facies, which well recorded the biotic and environmental processes through the great P-Tr transition in the shallow non-microbialite carbonate facies, has been studied in Yangou, Leping County, Jiangxi Province. The P-Tr sequence is well correlated with the Meishan section according to the conodont biostratigraphy and the excursion of carbon isotopes. A series of high-resolution thin-sections from the P-Tr boundary carbonate rocks at the Yangou section are studied to explore the interrelation between environmental change and biological evolution during the transitional time. Six microfacies have been identified based upon the observation of the thin-sections under a microscope on the grains and matrix and their interrelation. Combined with the data of fossils and carbon isotopes, Microfacies 4 (MF-4), coated-grain-bearing foraminifer oolitic sparitic limestone, and Microfacies 6 (MF-6), dark shelly micritic limestone, should be the different responses to the two episodes of mass extinction and environmental events that can be correlated throughout South China and even over the world. The oolitic limestone of MF-4 is the first finding from the latest Permian strata in South China and it might be a proxy of an unusual environmental condition of high pCO2, low sulfate concentration and of microbial blooming in the aftermath of the latest Permian mass extinction. The micritic limestone of MF-6 containing rich micro-gastropods and ostracods probably represents the blooming event of disaster taxa in the earliest Triassic environment. The microfacies analysis at the Yangou section can well reveal the episodic process of the biological evolution and environmental change in the shallow non-microbialite carbonate facies throughout the great P-Tr transition, thus the Yangou section becomes an important complement to the Meishan section. 相似文献
59.
Nearly 15 years after the proposal of the superanoxia concept (Isozaki, Y., 1994. Superanoxia across the Permo–Triassic boundary: record in accreted deep-sea pelagic chert in Japan. In: Embry, A.F., Beauchamp, B., Glass, D.J. (Eds.), Pangea: Global Environments and Resources. Memoir, Canadian Society of Petroleum Geologists, 17, pp. 805–812.), it is an appropriate timing to re-evaluate its geological context with the updated dataset. Kakuwa (Kakuwa, Y., 2008. Evaluation of palaeo-oxygenation of the ocean bottom across the Permian–Triassic boundary. Global and Planetary Change 63, 40–56.) lately discussed that the deep-sea anoxia across the Permian–Triassic boundary (P–TB) may have been much shorter than previously proposed, on the basis of ichnofabrics and geochemical data; however, his interpretations of the data do not appear straightforward nor persuading, and thus his claim is likely misled. Here we raise comments to his explanation on the following four issues: 1) invalid application of ichnofabric indices for shallow sea sediments to deep-sea cherts, 2) misinterpretation of Ce anomaly as a redox indicator, 3) improper application of various redox sensitive trace elements, and 4) questionable interpretations of δ34S data of pyrites. 相似文献
60.
M. Reuter W. E. Piller M. Harzhauser O. Mandic B. Berning F. Rögl A. Kroh M.-P. Aubry U. Wielandt-Schuster A. Hamedani 《International Journal of Earth Sciences》2009,98(3):627-650
In the central Iranian Esfahan-Sirjan and Qom basins sedimentation of the Oligo-/Miocene Qom Formation took place on extensive
mixed carbonate–siliciclastic ramps. During this time, both basins were positioned at the Eurasian margin of the Tethyan Seaway,
which connected the western and eastern regions of the Tethys Ocean at least until the late Burdigalian. During the so-called
Terminal Tethyan Event the Tethyan Seaway was then closed due to the collision of the African/Arabian and Iranian/Eurasian
plates. Facies analysis of the sedimentary record of both basins indicates paleoenvironments ranging from terrestrial to open
marine settings, including mangrove, restricted inner shelf lagoon, seagrass meadow, reefal, and deeper offshore environments.
Recognition of eight depositional sequences and elaboration of an integrated biostratigraphic framework (calcareous nannoplankton,
planktic and larger benthic foraminifers, gastropods, and pectinids) allow us to construct a basin-spanning stratigraphy.
The assignment of the recognized sea-level lowstands to the Ru 3 to Bur 3 lowstands of the global sea-level curve enables
a comparison with time-equivalent sections from the Zagros Basin, which was part of the African/Arabian Plate on the opposing
southern margin of the Tethyan Seaway. The so calibrated sections display restrictions of the Tethyan Seaway and interruption
of the south Iranian gateways between the Qom Basin and the Proto-Indopacific in relation to ongoing plate collision during
the early Burdigalian. 相似文献