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681.
本文描述了产自浙江长兴泗安五通组中的几种楔叶类化石Eviostachya hoegii(Stockmans)、Arch-aeocalamites sp.、Hamatophyton verticillatum Gu et Zhi、Sphenophyllum pseudotenerrimum(Sze)和Sphenophyllostachys sp.等.特别是Eviostachya hoegii的发现,为浙江晚泥盆世地层进行国际性对比,提供了新的依据. 相似文献
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683.
M. M. Joachimski R. van Geldern S. Breisig W. Buggisch J. Day 《International Journal of Earth Sciences》2004,93(4):542-553
Oxygen isotope ratios of well-preserved brachiopod calcite and conodont apatite were used to reconstruct the palaeotemperature history of the Middle and Late Devonian. By assuming an oxygen isotopic composition of –1 V-SMOW for Devonian seawater, the oxygen isotope values of Eifelian and early Givetian brachiopods and conodonts give average palaeotemperatures ranging from 22 to 25 °C. Late Givetian and Frasnian palaeotemperatures calculated from 18O values of conodont apatite are close to 25 °C in the early Frasnian and increase to 32 °C in the latest Frasnian and early Famennian. Oxygen isotope ratios of late Givetian and Frasnian brachiopods are significantly lower than equilibrium values calculated from conodont apatite 18O values and give unrealistically warm temperatures ranging from 30 to 40 °C. Diagenetic recrystallization of shell calcite, different habitats of conodonts and brachiopods, as well as non-equilibrium fractionation processes during the precipitation of brachiopod calcite cannot explain the 18O depletion of brachiopod calcite. Moreover, the 18O depletion of brachiopod calcite with respect to equilibrium 18O values calculated from conodont apatite is too large to be explained by a change in seawater pH that might have influenced the oxygen isotopic composition of brachiopod calcite. The realistic palaeotemperatures derived from 18O apatite may suggest that biogenic apatite records the oxygen isotopic composition and palaeotemperature of Palaeozoic oceans more faithfully than brachiopod calcite, and do not support the hypothesis that the 18O/16O ratio of Devonian seawater was significantly different from that of the modern ocean. 相似文献
684.
南秦岭泥盆系成矿带热水沉积成矿系列 总被引:1,自引:0,他引:1
南秦岭中晚古生界沉积区属造山前盆地,中泥盆世发生的海底喷流沉积事件及随后进入造山期的构造发展进程决定了本区成矿作用的基本类型及其演化。产于泥盆系中的各类铅锌矿床、铜矿床和金矿床不同程度具层控性质,矿化均与以钠长岩、硅质岩、富铁镁碳酸盐岩为特征的热水沉积或蚀变有较密切联系。基于矿床时空分布,矿物组合及共生顺序以及成矿作用演化的分析,确定它们可能是一个与热水沉积作用有关的成矿系列。这个成矿系列的建立对我国西部古生代褶皱带区域成矿研究有重要对比意义。 相似文献
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686.
记述了采自广西永福附近泥盆系的一鱼类化石标本。根据头甲轮廓和内颅特征,将其归入节甲鱼类。头甲的宽度大于后松果区长度,中颈片为梯形,后边缘片有较长的后突。内颅吻囊与筛后一枕区分开,耳区短;前眶后突不明显,位置靠后;后眶后突明显,远端不分叉。因此新材料应归入巴坎鱼属(Buchanosteus)。但眼孔大并朝向背侧上方,骨片上粒状突起纹饰的冠部和基部没有星状嵴等特征与Buchanosteus confertituberculatus(Chapman)不同,所以新材料应代表一新种,即Buchanosteus兴guangxiensis sp.nov.。还对澳大利亚与中国华南地区当时的古地理关系进行了讨论。 相似文献
687.
J. Hladil M. Gersl L. Strnad J. Frana A. Langrova J. Spisiak 《International Journal of Earth Sciences》2006,95(4):703-723
Mineral dust and other constituents of Devonian atmospheric aerosols together with certain amounts of aquatic suspensions of riverine detrital origin, colloidal particle dispersions and seawater solutes were embedded in ~95–98% (or purer) limestones on a consistently subsiding isolated carbonate platform where they formed very complex impurity systems. Very low Th/U values, relative abundance of Fe but a slight excess of K typically characterize these ultrafine impurities which are mineralogically dominated by smectite–illite and mica (sericite) together with goethite. In vertical section, these impurities are arranged like incremental series of light and dense bands. The combined method of natural gamma-ray spectrometric and magnetic susceptibility measurements (GRS–MS) together with background of major and trace element analyses provided first systematic insights into fine-scale variability of these impurities in a pile of pure carbonate platform beds, mostly in inner platform Amphipora limestone facies. These carbonates were deposited close to sea level but far from river mouths, and they represented a certain sort of a relatively “independent” medium that was primarily sensitive to climatically (and by rare events) controlled input of atmospheric dust. A remarkable similarity of MS stratigraphic patterns that reflect the quantity and quality of embedded impurities in very distant and paleogeographically separated Devonian basins might be seen as supporting this viewpoint. A long composite stratigraphic section of the Moravian Karst ranges from mid-Eifelian to end-Frasnian levels and yields a number of time characterizing GRS–MS variations that can potentially serve as templates for high-resolution stratigraphic correlations over long distances.Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users. 相似文献
688.
689.
Sachiko Agematsu Katsuo Sashida Sirot Salyapongse Apsorn Sardsud 《Journal of Asian Earth Sciences》2006,26(6):605-611
A Lower Devonian (Emsian) tentaculite fauna including Nowakia acuaria [Richer, R., 1854. Thüringische Tentaculiten. Zeitschr. Deutsch. Geol. Gesellsch. 6, 275–290] occurs in black shale in the basal part of a siliciclastic sequence exposed north of Satun, southern peninsular Thailand. Similar tentaculite beds with Nowakia have been reported from several areas in the Fang, Sri Sawat, and Trang areas of Thailand, the Langkawi Islands and the Mahang–Baling areas of Malaysia. The depositional environments in which the tentaculite-bearing black shale accumulated extended from modern northern Thailand to northwestern Malaysia during the Early Devonian (Emsian). 相似文献
690.