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41.
Fossil assemblages of the Ordovician to Devonian successions of Japan suggest complex temporal, environmental and geographical controls on their biogeographical signature. Thus, limited similarity at the species‐level between the trilobite, brachiopod and ostracod faunas of the South Kitakami, Hida‐Gaien and Kurosegawa terranes in part reflects the sporadic stratigraphic distribution of shelly fauna within these terranes. As a result, and with the exception of corals and pan‐tropical radiolarians, species‐level similarities are greater with other regions of East Asia and Australia than amongst the Japanese terranes. The Silurian faunas of the South Kitakami Terrane have affinities with North America, Europe, Central Asia and Australia, but there is no overriding signature to support proximity either to South China or Gondwana. Notably, brachiopod and trilobite faunas of the Middle Devonian suggest strong connections with North China. Trilobite, coral and ostracod faunas of the Hida‐Gaien Terrane show affinity, including at species level, with Siluro‐Devonian faunas from westerly‐situated palaeocontinents, especially those of Central Asian and European affinity, suggesting a continuation of the Central Asian Orogenic Belt, or of its associated lithofacies. Greater diversity of groups such as ostracods and trilobites in this terrane may signal closer links with continental shelf faunas of East Asia. The dominant biogeographical signature of the Kurosegawa Terrane is from corals and trilobites, suggesting links with the Siluro‐Devonian of Central Asia, Australia and South China. The variable biogeographic signal of the Japanese faunas may reflect the lifestyles of organisms with different physiologies and larval dispersal mechanisms, as well as the relative incompleteness of the Japanese fossil record. The present state of knowledge of the faunas cautions against placing Japan in relative proximity to the North or South China plates, or of presenting the Japanese terranes as a unified island arc to the north of the South China Plate during the Early Palaeozoic. 相似文献
42.
Establishing a precise chorology is a critical issue when employing cold-water coral as paleoenvironmental archives. Currently, U-Th, 14C and 210Pb dating techniques are the most frequently used methods. The high-magnesium calcite skeleton of bamboo coral has clear growth bands, which is appropriate for 14C and 210Pb dating methods and holds a great potential to be high-resolution archives of mid-to-deep ocean evolution. Aragonitic stony coral is appropriate for both U-Th and 14C dating methods, which is valuable in paleoceanographic research. Because the U-Th method can provide the absolute chronology of coral samples, it can further be used to calculate the 14C age of ocean carbon reservoirs. Therefore, U-Th and 14C dating results of stony coral are currently the most reliable data for exploring the evolution of ocean carbon reservoirs through the Last Glacial Maximum to the present. It has been found that the 14C ventilation ages of intermediate water masses of the equatorial Atlantic and Southern Ocean significantly decreased at the end of the Heinrich Stadial 1. This suggests a massive carbon transfer from deep oceans to the atmosphere, or the Atlantic intermediate depths were ventilated by the southern- and the northern-sourced water masses, respectively, before and after the Heinrich Stadial 1. 相似文献
43.
N. V. Goreva A. S. Alekseev T. N. Isakova O. L. Kossovaya 《Stratigraphy and Geological Correlation》2009,17(1):43-61
Micro- and macrofauna remains were studied from transitional deposits of Moscovian and Kasimovian Stages in the Donskaya Luka (Volgograd Region). The preliminary analysis of microfauna showed that “sub-Triticites Beds” of the Donskaya Luka contain fusulinid and conodont assemblages enabling correlation of the Middle and Upper Carboniferous deposits in the study region with the type sections of Moscow area and Donbass. Conodonts from the “sub-Triticites Beds” stratotype were studied for the first time. As is established, upper part of the Sukhov Fm. and the base of the Seleznev Fm. belong to the Protriticites pseudomontiparus-Obsoletes obsoletus Zone. Based on fusulinids, higher parts of the Seleznev Fm. belong to the Montiparus Zone of the Khamovnikian Substage, whereas conodonts suggest their correlation with lower part of the Khamovnikian Substage, i.e., with the Ratmirovo Fm. or a basal part of the Neverovo Fm. Middle part of the Seleznev Fm. is correlated to middle cycle of the Neverovo Fm. of the Khamovnikian Substage in Moscow area. The Middle-Upper Carboniferous boundary deposits of the Donskaya Luka are represented by deposits of extremely shallow-water settings and contain only sporadic microfauna. These sections cannot be considered as possible candidates for the GSSP of the Kasimovian Stage base. 相似文献
44.
Mai Miyamoto Masashi Kiyota Hiroto Murase Takeshi Nakamura Takeshi Hayashibara 《Marine Geodesy》2017,40(4):205-223
We investigated the effects of the spatial resolution of bathymetry data on the predicted local distribution of large gorgonian corals on the southern Emperor Seamounts in the high seas of North Pacific. Terrain attributes were calculated from bathymetric survey data at six different grid-cell sizes (25–800 m) to investigate how the values of bottom terrain attributes and the prediction of MaxEnt habitat suitability models would vary with grid-cell size. The values of each terrain attribute showed different patterns among different grid-cell sizes, and MaxEnt demonstrated better performance at grid-cell size of 100 m or less than at larger sizes. 相似文献
45.
46.
Strontium stable isotopes fractionate in the soil environments? 总被引:1,自引:0,他引:1
Ludwik Halicz Irina Segal Noa Fruchter Mordechai Stein Boaz Lazar 《Earth and Planetary Science Letters》2008,272(1-2):406-411
This study shows that the stable isotopic composition of strontium (the 88Sr/86Sr ratio expressed as δ88/86Sr value relative to the NBS987 standard) varies significantly in sedimentary terrestrial environments. The abundances of 86Sr, 88Sr isotopes were analyzed by MC-ICP-MS “Nu Plasma”. All studied rocks and waters show δ88/86Sr values that are distinctly different from the measured NBS987 standard (yielding 0.01 ± 0.05‰, all errors are reported as 2σ). Modern corals from the northern Gulf of Aqaba, Red Sea yielded significantly different value than seawater (δ88/86Sr = 0.22 ± 0.07‰, compared to 0.35 ± 0.06‰, respectively), in an excellent correlation with the δ88/86Sr analyses reported by Fietzke and Eisenhauer [Fietzke, J., Eisenhauer, A., 2006. Determination of temperature-dependent stable strontium isotopes (88Sr/86Sr) fractionation via bracketing standard MC-ICP-MS. Geochm. Geophys. Geosyst. 7 (no. 8)] on other coral samples. All carbonate samples that originated in the marine environment: corals (porites and acropora from the northern Gulf of Aqaba); Cretaceous limestone and runoff from the Judea Mountains as well as lacustrine evaporitic aragonite (Dead Sea); and Red Sea and Atlantic seawater yield an average δ88/86Sr value of 0.26 ± 0.1‰. On the other hand, secondary materials (products of chemical weathering) from the terrestrial environment of the Judea Mountain such as terra rossa soil and speleothem calcite (that derives its Sr from the above-lying soil) yielded significantly lower δ88/86Sr value of − 0.17 ± 0.06‰. This indicates that strontium isotopes fractionate in the soil environment calling for a possible development of strontium isotopes as a tracer for processes of chemical weathering and pedogenesis. 相似文献
47.
中国及邻区石炭纪构造古地理及生物古地理 总被引:1,自引:0,他引:1
本文包括3部分:(1)扼要回顾了中国及邻区晚海西阶段的地质构造背景和构造古地理特征。根据全球构造活动论和地壳发展阶段论的观点,把中国及邻区晚海西阶段的大地构造单元分为4个构造域,10个亚构造域。(2)论述中国和世界石炭纪生物古地理分区。根据四射珊瑚和腕足动物群分析,把全球早石炭世生物古地理区系分为两个生物大区、6个生物区和8个生物亚区。在中国境内对生物亚区内部生物地方中心的分异作了进一步划分。(3)简述中国石炭纪古地理和某些有关的沉积矿产。中国石炭系矿产除了重要的煤以外,还有石膏矿、铝土矿和不同类型的铁矿。这些沉积矿产的分布主要受到古气候、古地理和构造条件的控制。 相似文献
48.
柴达木盆地北缘石灰沟晚石炭世的四射珊瑚 总被引:2,自引:0,他引:2
青海省柴达木盆地北缘晚石炭世地层出露完好,四射珊瑚化方丰富。本文研究了该区晚石炭世四射珊瑚26属,49种和亚种,10个未定种。自下而上建立了5个四射珊瑚组合带:1Lithostrotionella-Thysanophyllum组合带;2Cgathaxomia-Rotiphyllum组合带;3Protoivanovia-Amplexus组合带;4NeokonickoPhyllum-Koninckophgllam组合带;5Pseudozaphretoides-Lophocarinophyllam组合带。 相似文献
49.
热带与亚热带拥有大量丰富的自然资源,同时也正在经历着快速的城市化进程,其资源、生态、环境等都面临着前所未有的挑战。同时,热带与亚热带地区存在着大量的自然灾害(如台风、干旱、地震等),威胁着该地区人类经济社会的可持续发展。应用遥感技术对热带与亚热带区域进行全面的监测,对于热带与亚热带区域甚至全球的可持续发展具有重要的意义。然而,由于热带与亚热带特殊的地理条件(如多云多雨等),遥感监测需要克服特殊的技术挑战。本文通过Web of Science核心数据库的7594篇研究论文进行分析,综述了热带与亚热带遥感的研究现状,分别从热带与亚热带遥感的需求、现状、挑战和机遇,通过共被引文献分析和主题词频率分析,建立共被引文献网络和主题词网络,并通过非监督机器学习进行聚类,分别识别出22个共被引文献聚类和6个主题词聚类。通过对这些共被引文献类别和主题词类别的深入分析,本文总结了:(1)热带与亚热带遥感研究的主要监测对象,包括城市地表、热带雨林、红树林、珊瑚、热带草原、生物多样性和自然灾害;(2)热带与亚热带遥感主要采用的遥感技术,包括:遥感数据的选择和使用、遥感数据分析的方法、多云多雨的问题应对以及多源遥感技术。最后,从现代遥感技术的快速发展,本文从8个方面讨论热带与亚热带遥感面临的挑战和未来发展的机遇。 相似文献
50.
Amphipoda are a diverse and important faunal component of deep‐sea habitats worldwide. However, relatively little is known about species that are associated with cold‐water corals, in particular concerning their genetic diversity, population genetic processes, population differentiation, and potential host specificity. We exemplarily investigate these questions studying three pleustid species—Stenopleustes aff. malmgreni (Boeck, 1871), Stenopleustes aff. nodifera (Sars, 1883) and Neopleustes aff. boecki (Hansen, 1888)—that are associated with cold‐water corals and polychaete assemblages along the Reykjanes Ridge southwest of Iceland. We sequenced mitochondrial COI and performed ddRAD to study thousands of nuclear loci. These species and a pair of morphologically cryptic species within Stenopleustes aff. nodifera were consistently delimited by COI and ddRAD. We conclude that all of our studied species are new to science, raising the number of pleustids reported from cold‐water corals to six. Two species were collected only once, and these species exhibited high levels of inbreeding, suggesting little exchange with other populations, which might be a result of strong host specificity. The other two species were wider distributed, with very low differentiation among populations, even between populations separated by 130 km. These species showed signs of recent population expansions, possibly in relation to changes in the cold‐water coral associated ecosystem (e.g., due to glacial cycles and/or volcanic or geothermal activities). They had lower levels of inbreeding and were each associated with three different host coral species, which might facilitate dispersal and gene flow. Our results show divergent population genetic patterns for the studied pleustid species. These might be attributed to the species’ host specificity and highlight important differences among species with seemingly similar life‐styles. Species diversities appear to be greatly underestimated, limiting our abilities to truly assess the vulnerability of the fauna living in these threatened cold‐water coral habitats. 相似文献