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11.
董发勤 李刚 代群威 周琳 王富东 赵学钦 蒋忠诚 张强 李博文 Enrico Capezzuoli Mike O''Driscoll Andelka Plenkovic-Moraj 《中国岩溶》2021,40(1):11-18
钙华不仅具有重要的景观旅游价值,而且对确定区内碳酸盐沉积特征、环境演化规律及同期环境生物的作用与贡献有重要的研究意义。本文在对比国内外典型钙华特征的基础上,以黄龙和九寨沟为例,对雪宝顶区块流域内钙华的沉积特征、环境化学与生物作用进行阐述,指出了雪宝顶区块流域冷水型钙华的形成与演化是化学沉积-溶解作用、生物沉积与溶蚀作用等共同作用的结果,并受非生物、生物因素影响。在雪宝顶冷水型钙华的形成过程中,微生物协同参与了钙华的沉积与溶蚀过程,通过自身新陈代谢促活动促使使钙离子结晶,并诱导晶型变化;其他生物体如植物、藻类等或以间接的方式促进或加快了钙华形成,或为钙华生长提供模板和体量。 相似文献
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Mark J. Sier Wil Roebroeks Corrie C. Bakels Enrico Brühl Dimitri De Loecker Norbert Hesse Lutz Kindler Thomas Laurat Herman J. Mücher Kirsty E.H. Penkman Douwe J.J. van Hinsbergen 《Quaternary Research》2011,75(1):213-218
An interdisciplinary study of a small sedimentary basin at Neumark Nord 2 (NN2), Germany, has yielded a high-resolution record of the palaeomagnetic Blake Event, which we are able to place at the early part of the last interglacial pollen sequence documented from the same section. We use this data to calculate the duration of this stratigraphically important event at 3400 ± 350 yr. More importantly, the Neumark Nord 2 data enables precise terrestrial-marine correlation for the Eemian stage in central Europe. This shows a remarkably large time lag of ca. 5000 yr between the MIS 5e ‘peak’ in the marine record and the start of the last interglacial in this region. 相似文献
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In this paper we describe an example of travertine fissure-ridge development along the trace of a normal fault with metre
displacement, located in the eastern margin of the Neogene–Quaternary Siena Basin, in the Terme S. Giovanni area (Rapolano
Terme, Italy). This morphotectonic feature, 250 m long, 30 m wide and 10 m high, formed from supersaturated hot waters (39.9°C)
flowing from thermal springs aligned along the trace of the normal fault dissecting travertines not older than Late Pleistocene
(24 ± 3 ka). A straight, continuous fissure with a maximum width of 20 cm occurs at the top of the ridge, along its crest.
Hot fluids flow from cones mainly located at the extremities of the ridge, where travertine is depositing. The travertine
fissure-ridge shows an asymmetrical profile since it buries the fault scarp. The difference in height of slopes corresponds
to the vertical displacement of the normal fault. Fissuring of the recent travertine deposits along the strike of the crestal
fissure, as well as recent hydrothermal circulation, lead us to believe that the Terme S. Giovanni normal fault may be currently
active. On the whole, the Terme S. Giovanni fissure ridge can be defined as a travertine fault trace fissure-ridge, adding
a helpful example for studying the relationship between faulting and travertine deposition. 相似文献
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The origin of oceanic islands has been the subject of much speculation, starting with Darwin almost two centuries ago. Two classes of oceanic islands can be identified: ‘volcanic islands’, which form due to excess volcanism caused by melting anomalies in the suboceanic mantle, and ‘tectonic islands’, which form due to transpressive and/or transtensional tectonics of blocks of oceanic lithosphere along transform faults. Modern and sunken tectonic islands from the Atlantic Ocean and Indian Ocean and the Caribbean Sea and Red Sea expose mantle and lower‐crust lithologies and display an elongated narrow morphology; in contrast, volcanic islands expose basalts and have near‐circular morphology. Both are often capped by carbonate platforms. The life cycle of tectonic islands tends to be more complex than that of most volcanic islands; their elongated narrow morphology, together with their tectonic instability and high seismicity, affect the architecture of the carbonate platforms capping them, limiting coral reef development and favouring rhodalgal–foramol biota associations. 相似文献
16.
Silvia Trini Castelli Enrico Ferrero Dominico Anfossi 《Boundary-Layer Meteorology》2001,100(3):405-419
In this work, three turbulence closure models, Mellor andYamada level 2.5, E - l and E - implemented in a circulation model, are compared in neutral condition over complex terrain. They are firstly applied to a one-dimensional case on flat terrain and then to a schematic two-dimensional valley. The simulation results, in terms of wind field and turbulent kinetic energy, are tested against measurements from a wind-tunnel experiment. The empirical constants defining the characteristic length scales of the closures are modified based on turbulence parameters estimated in the experiment. The formulation of the diffusion coefficients is analysed to explain the differences among the various closures in the simulation results. Regarding the mean flow, both on flat and complex terrain, all the closures yield satisfactory results. Concerning the turbulent kinetic energy, the best results are obtained by E - l and E - closures. 相似文献
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对第一部分的实验结果进行了讨论,指出局地最大、最小涡度的存在与所谓的正压不稳定和大气中经常观测到的滚动涡有关。速度廓线中的拐点和涡度极大值点对应不稳定发展的位置。另外,为了改进湍流的模拟,根据“准正则”近似,发展了一个三阶闭合模式。这个模型已被证明可以描述与湍流过程有关的流体动力学变量的趋势。 相似文献
18.
基于GOODALL相近指数的遥感图像和其它空间数据综合分类方法 总被引:2,自引:0,他引:2
介绍DavidW.Goodall基于概率的相近指数理论,研究它被应用在遥感图像和其它空间数据综合分类中的可能性,并首次在GRASS环境下实现了基于DavidW.Goodall的相近指数的遥感图像和其它空间数据综合分类算法,并对该算法进行了测试,将分类结果 与其它几种较流行的分类方法结果进行了比较。 相似文献
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