The terrestrial fauna of the Late Triassic Pant-y-ffynnon Quarry fissures,South Wales,UK and a new species of Clevosaurus (Lepidosauria: Rhynchocephalia)     

Emily Keeble  David I. Whiteside  Michael J. Benton 《Proceedings of the Geologists' Association. Geologists' Association》2018,129(2):99-119

Pant-y-ffynnon Quarry in South Wales yielded a rich cache of fossils in the early 1950s, including articulated specimens of new species (the small sauropodomorph dinosaur Pantydraco caducus and the crocodylomorph Terrestrisuchus gracilis), but no substantial study of the wider fauna of the Pant-y-ffynnon fissure systems has been published. Here, our overview of existing specimens, a few described but mostly undescribed, as well as freshly processed material, provides a comprehensive picture of the Pant-y-ffynnon palaeo-island of the Late Triassic. This was an island with a relatively impoverished fauna dominated by small clevosaurs (rhynchocephalians), including a new species, Clevosaurus cambrica, described here from a partially articulated specimen and isolated bones. The new species has a dental morphology that is intermediate between the Late Triassic Clevosaurus hudsoni, from Cromhall Quarry to the east, and the younger C. convallis from Pant Quarry to the west, suggesting adaptive radiation of clevosaurs in the palaeo-archipelago. The larger reptiles on the palaeo-island do not exceed 1.5?m in length, including a small carnivorous crocodylomorph, Terrestrisuchus, and a possible example of insular dwarfism in the basal dinosaur Pantydraco.  相似文献   

Fractal reconstruction of sea-floor topography     

Jean-Claude Mareschal 《Pure and Applied Geophysics》1989,131(1-2):197-210

Sea-floor bathymetric profiles exhibit features at many different scales of length; this suggests that they could be described as fractals. An algorithm interpolating a fractal line between points has been used to reconstruct bathymetric profiles from a few data points. In general, this fractal line has the same Fourier amplitude spectrum as real bathymetry, and, if the parameters of the interpolation are suitably chosen, it has a very similar appearance. The success of this fractal reconstruction algorithm for the sea-floor raises the possibility that it could be used to extrapolate, from data collected at one scale, the properties of the sea-floor at finer scales, and that similar techniques could be used to interpolate a surface between bathymetric profiles. The fractal character is a sign that the processes that shape the sea-floor are scale invariant and suggests that the renormalization group technique could be used to model these processes.  相似文献   

多元统计在大洋玄武岩同位素端元识别中的应用          下载免费PDF全文

李曙光  肖越辉 《地质科学》1994,29(3):298-308

应用因子分析的方差最大旋转和非线性映射方法对海洋玄武岩Sr、Nd、Pb同位素数据在多维空间中的数据结构进行了分析。研究表明这些数据在多维空间中呈五角形结构,并对应5个地幔端元:大西洋中脊玄武岩(DMM),圣埃伦那(HIMU),鲸岛(EMI),萨摩亚岛(EMII)和DS(EMIII).其中DS(EMIII)是本文新识别出来的一个地幔端元,它可能是重新进入地幔的具有较高古老放射成因Pb的下地壳物质。  相似文献   

Carlsberg Ridge, northern Indian Ocean: gravity and isostasy   总被引：1，自引：0，他引：1  

B. Ashalatha  C. Subrahmanyam  R. N. Singh 《Geophysical Journal International》1994,119(1):69-77

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Microseismicity of the ultraslow-spreading Gakkel ridge, Arctic Ocean: a pilot study     

Vera Schlindwein  Christian Müller  Wilfried Jokat 《Geophysical Journal International》2007,169(1):100-112

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广义岭估计的直接解法   总被引：10，自引：0，他引：10  

游扬声  王新洲  刘星 《武汉大学学报(信息科学版)》2002,27(2):175-178

提出了广义岭估计的直接解法，该解法不需计算岭参数，可直接求得具有最小均方误差的解，并举例证实了该解法的优越性。  相似文献   

Electrical resistivity structure of the Valu Fa Ridge, Lau Basin, from marine controlled‐source electromagnetic sounding     

Lucy MacGregor  Martin Sinha  Steven Constable 《Geophysical Journal International》2001,146(1):217-236

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Azimuthal variation of the P phase in Icelandic receiver functions     

Vera Schlindwein 《Geophysical Journal International》2001,144(1):221-230

A curious observation has been made on radial receiver functions calculated from teleseisms recorded by 29 broad-band seismometers distributed over Iceland. The arrival time of the direct P phase of the radial receiver functions depends critically upon the azimuth of the teleseismic source. For a seismic station in West Iceland, the direct P  phase of the radial receiver function arrives consistently later for easterly source azimuths than for westerly source azimuths. The reverse applies for stations in East Iceland. In the original seismograms, the delayed P phase of the receiver function appears up to 450 ms later on the radial than on the vertical component. The seismometer locations in East and West Iceland are separated by the Neovolcanic Zone, a constructive plate boundary. The delayed P phases occur for seismic rays travelling across this zone. However, it is not obvious how wave propagation across the plate boundary zone could cause the observed delays. The tentative explanation proposed here involves the regional dip of the Icelandic lava sequences towards the Neovolcanic Zone. A dipping interface at shallow depth results in a P–S converted phase arriving shortly after the P phase. These phases cannot be separated in the radial receiver functions, given the bandwidth of the observed signals. However, a calculation of receiver functions from estimates of the P , SV and SH wavefields clearly reveals a P–S converted phase at about 500 ms for easterly source azimuths in West Iceland and for westerly source azimuths in East Iceland. The amplitudes of the direct P phase and the P–S phase converted at a dipping interface would be expected to vary strongly with azimuth in accordance with the observed behaviour.  相似文献   

西倾斜脊的生成移动与华北降水     

石林平  吉宝珩  迟秀兰  魏华 《气象》1996,22(11):26-28

该文介绍了河套至华北，华东地区一种西倾斜脊及其对天津和华北降水的影响。  相似文献   

东海陆架平湖海域改造砂沉积特征   总被引：3，自引：0，他引：3  

陈裕迅 《上海国土资源》1996,(1):40-47

东海陆架平湖海域分布的改造砂。其物质来源为晚更新世末生成的沙脊物质,是在晚更新世末至全新世初期间,原始物质被掀起再沉积的产物。  相似文献