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广东南雄盆地晚白垩系古地磁研究 总被引：2，自引：0，他引：2
对广东南雄盆地大凤－河南街剖面和古城－坪岭剖面上白垩统南雄组２５个采点，古新统上湖组２个采点的古地磁研究，经系统热退磁及倒转检验，分析出南雄组的特征剩磁方向为Ｄ＝３２．７°，Ｉ＝２７．４°，Ｋ＝１６．１，α９５＝８．４°，Ｎ＝２０；显示晚白垩世时期华南大陆位于１４．５°Ｎ的位置，同时晚白垩世以后华南大陆可能普发生较大规模的顺时针旋转。 相似文献
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硅藻门沟纹藻属在我国是１个新记录的属。核属最先由Ｋｏｌｂｅ（１９５４）在西太平洋赤道区（２°５２＇Ｓ，８９°５０＇Ｗ，水深３２２５ｍ）的柱状样沉积物中找到１种，订名Ｌ．ｐｅｔｔｅｒｓｓｏｎｉｉ。之后，又在１９５５年从大西洋（０°７＇Ｎ，１９°１２＇ｅ；０°８′Ｎ，１６°１９′Ｅ）和太平洋（６°４４′Ｎ，１２９°２８′Ｗ；２°５２′Ｓ，８９°５′Ｗ）的柱状样沉积物中找到另１种，订名Ｌ．ｈｕｓｔｅｄｔ 相似文献
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从大气ＣＯ_２的测量来推断北半球植被增加的活动性Ｃ．Ｄ．Ｋｅｅｌｉｎｇ等大气ＣＯ２季节性变化的大部分详细记录是在夏威夷ＭａｎｎａＬｏａ观察站（２０°Ｎ，１５６°Ｗ）获得的．利用年间离散记录通过计算一个由４个函数组成的、相位不变、振幅随时间线性增加的调?.. 相似文献
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赤道非洲（布隆迪）高地泥炭沼泽的￣（１３）Ｃ值与晚第四纪生物群体的变化Ａ，Ｍ．Ａｕｃｏｕｒ等卡希如（Ｋａｓｈｉｒｕ）泥炭沼泽（３°２８′Ｓ，２９°３４′Ｅ，海拨２２４０ｍ）是布隆迪高地４ｋｍ￣２汇水区域内一个０．５ｋｍ￣２的小洼地，汇水区域的最大海拨... 相似文献
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Ｋ－Ｔ界线生物灭绝：地质史上的瞬时事件，还是渐变事件？Ｒ．Ｃｏｃｃｉｏｎｉ等笔者在西班牙东南部卡拉瓦卡剖面（北纬３８°０４′３５″，西经１°５２′４０″）对底栖有孔虫记录进行了高分辨率分析。该剖面是Ｋ－Ｔ界线记录最完整的６个陆上剖面之一，成为解释Ｋ－... 相似文献
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为搞清楚黄河三角洲的发育以及黄河三角洲进积和贝壳堤形成的关系 ,在黄河三角洲两个站位上打了钻。因为岩心采取率的原因 ,Ｈ９６０１站位打了两个紧相邻的钻孔（Ⅰ ,Ⅲ） ,该站位位于３７°４０．５′Ｎ、１１８°２８．７′Ｅ ,山东省境内现代黄河三角洲之上 ,１８５５年海岸线和第二道贝壳堤（原文中称作贝壳堤Ｈ２）东北 ,孔口高程 +５．５ｍ。Ｈ９６０２站位只有一个钻孔Ⅱ ,位于山东省境内３７°４．８′Ｎ、１１８°５４．３′Ｅ，１８５５年海岸线和第二道贝壳堤之西南 ,第三道贝壳堤（原文中称作贝壳堤Ｈ１）之东北 ,Ｈ９６０１站… 相似文献
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印度东海岸苏伯尔讷雷卡河的重金属分布Ｎ．Ｋ．Ｓｅｎａｐａｔｉ等源于半岛的苏伯尔讷雷卡河流域有一个约１９２９６ｋｍ２的非对称汇水盆地。由源头焦达讷格布尔高地的兰契高原（北伟２３°１８＇，东经８５°１１＇）至河口孟加拉湾（北伟２１°３４＇，东经８７°２１... 相似文献
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从格陵兰获取的完整冰期旋回的第一个甲磺酸盐和硫酸盐的冰心记录ＭａｒｇａｒｅｔａＥ．Ｈａｎｓｓｏｎ等伦兰（Ｒｅｎｌａｎｄ）冰心是在格陵兰钻取的第三个由表面至基岩的冰心。它是１９８８年由北欧联合项目在东格陵兰（７１．２°Ｎ,２６．４°Ｗ）斯科斯比松峡湾一... 相似文献
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Chandralata Raghukumar G. Sheelu P. A. Loka Bharathi Shanta Nair C. Mohandass 《Marine Georesources & Geotechnology》2001,19(1):1-16
In order to assess the impact of deep-sea mining on the in situ benthic life, we measured the microbial standing stock and concentration of organic nutrients in the deep-sea sediments of the Central Indian Ocean Basin in the Indian pioneer area. Sediments were collected using box core and grab samples during September 1996. The total bacterial numbers ranged from 10 10 -10 11 cells per g -1 dry weight sediment. There was a marginal decrease in the number of bacteria from surface to 30 cm depth, though the subsurface section registered a higher number than did the surface. The highest numbers were encountered at depths of 4-8 cm. The retrievable number of bacteria were two orders less in comparison with the direct total counts of bacteria. An almost homogeneous distribution of bacteria, total organic carbon, living biomass, and lipids throughout the depth of cores indicates active microbial and benthic processes in the deep sea sediments. On the other hand, a uniform distribution of total counts of bacteria, carbohydrates, and total organic carbon in all the cores indicates their stable nature and suggests that they can serve as useful parameters for long-term monitoring of the area after the benthic disturbance. Further studies on temporal variability in this region would not only verify the observed norms of distribution of these variables but would also help to understand restabilization processes after the simulated benthic disturbance. 相似文献
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Derek V. Ellis 《Marine Georesources & Geotechnology》2001,19(1):51-63
This article reviews information recently available from existing marine and coastal mining for responses to environmental issues affecting marine mining at different depths. It is particularly but not exclusively concerned with those issues affecting seabed biodiversity impact and recovery. Much information has been gathered in the past 10 years from shallow mining operations for construction aggregate, diamonds, and gold, from coastal mines discharging tailings to shallow and deep water, and from experimental deep mining tests. The responses to issues identified are summarized in a series of eight tables intended to facilitate site-specific consideration. Since impacts can spread widely in the surface mixing layer SML, and can affect the biologically productive euphotic zone, the main issues considered arise from the depth of mining relative to the SML of the sea. Where mining is below the SML, the issue is whether it is environmentally better to bring the extraction products to the surface vessel for processing (and waste discharge), or to process the extraction products as much as possible on the seabed. Responses to the issues need to be sitespecific, and dependent on adequate preoperational environmental impact and recovery prediction. For deep tailings disposal from a surface vessel, there are four important environmental unknowns: (1) the possible growth of "marine snow" (bacterial flocs) utilizing the enormous quantities of fine tailings particles (hundreds or thousands of metric tons per day) as nuclei for growth, (2) the possibility that local keystone plankton and nekton species may migrate diurnally down to and beyond the depth of deep discharge and hence be subjected to tailings impact at depth, (3) the burrow-up capability of deep benthos and their ability to survive high rates of tailings deposition, and (4) the pattern and rate of dispersion of a tailings density current through the deep water column from discharge point to seabed. Actions to obtain relevant information in general and site-specifically are suggested. 相似文献
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G. Parthiban 《Marine Georesources & Geotechnology》2000,18(3):223-235
Particle fluxes were measured 7 m above the sea bottom during the predisturbance, disturbance, and postdisturbance periods by using time series sediment traps attached to seven deep-sea moorings deployed in the INDEX experiment site in the Central Indian Basin. The predisturbance particle fluxes varied between 22.3 to 55.1 mg m -2 day -1 . Increased and variable particle fluxes were recorded by the sediment traps during the disturbance period. The increase observed was 0.5 to 4 times more than the background predisturbance fluxes. The increases in particle fluxes (~4 times) recorded by the sediment trap located in the southwestern direction (DMS-1) were the greatest, which could be the result of preferential movement of resuspended particles generated during the deep-sea benthic disturbance along the general current direction prevailing in this area during the experimental period. Also, the traps located closer to the disturbance area recorded greater fluxes than did the traps far away, across the Deep Sea Sediment Resuspension System path. This variability in recorded particle fluxes by the traps around the disturbance area clearly indicates that physical characteristics such as grain size and density of the resuspended particles produced during the disturbance had an important effect on particle movement. The postdisturbance measurements during ~5 days showed a reduction in particle fluxes of ~50%, indicating rapid particle settlement. 相似文献
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Arne Schnack-Friedrichsen Angela M. Davis Jim D. Bennell Dei G. Huws 《Marine Georesources & Geotechnology》2001,19(4):221-243
The interdependence between the seismo-acoustic properties of a marine sediment and its geotechnical/physical parameters has been known for many years, and it has been postulated that this should allow the extraction of geotechnical information from seismic data. Though in the literature many correlations have been published for the surficial layer, there is a lack of information for greater sediment depths. In this article, a desktop study on a synthetic seafloor model illustrates how the application of published near-surface prediction equations to subsurface sediments (up to several tens of meters burial depth) can lead to spurious predictions. To test this further, acoustic and geotechnical properties were measured on a number of sediment core samples, some of which were subjected to loading in acoustically-equipped consolidation cells (oedometers) to simulate greater burial depth conditions. For low effective pressures (representing small burial depths extending to around 10 meters subsurface), the general applicability of established relationships was confirmed: the prediction of porosity, bulk density, and mean grain size from acoustic velocity and impedance appears generally possible for the investigated sedimentary environments. As effective pressure increases through, the observed relationships deviate more and more from the established ones for the near-surface area. For the samples tested in this study, in some instances increasing pressure even resulted in decreasing velocities. There are several possible explanations for this abnormal behavior, including the presence of gas, overconsolidation, or bimodal grain size distribution. The results indicate that an appropriate depth correction must be introduced into the published prediction equations in order to obtain reliable estimates of physical sediment properties for greater subsurface depths. 相似文献
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海上大直径钢管桩打桩过程中,桩周土体受到强烈扰动而发生强度弱化,掌握桩周土体强度弱化规律对于准确预测打桩过程、保证工程安全具有重要意义。为研究土体强度弱化规律,开展了环剪试验模拟打桩对桩周土体的扰动,测试土体强度随剪切速率的变化规律,建立了描述土体强度弱化规律的拟合公式,引入到打桩分析软件中。研究结果表明：土体的强度折减程度不仅与土体本身的性质有关还受到土体的埋深和剪切速率的影响,埋深越深土体强度折减程度越低,剪切速率越高土体强度折减越高,在打桩分析中可采用这里推荐的线性折减方法来模拟不同深度处土体强度的折减规律。 相似文献
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Geoacoustic Inversion via Genetic Algorithm and Its Application to Manganese Sediment Identification
An acoustic inversion method using a wide-band signal and two near field receivers is proposed and applied to multiple layered seabed models including a manganese sediment. The inversion problem can be formulated into a probabilistic model comprised of signals, a forward model, and additive noise. The forward model simulates wide-band signals, such as chirp signals, and is chosen to be the source-waveletconvolution plane wave modeling method. The wavelet matching technique, using weighted least-squares fitting, estimates the sediment sound-speed and thickness on which determination of the possible numerical ranges for a priori uniform distribution is based. The genetic algorithm is applied to a global optimization problem to find a maximum a posteriori solution for determined a priori search space. Here the object function is defined by an L 2 norm of the difference between measured and modeled signals. Not only the marginal pdf but also its statistics are calculated by numerical evaluation of integrals using the samples selected during importance sampling process of the genetic algorithm. 相似文献
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The advanced piston corer (APC) has been used by the Ocean Drilling Program since 1985 for recovering soft sediments from the ocean floor. The pullout force measured on extracting the core barrel from the sediment is shown to correlate with the average shear strength of the sediment core measured in the ship's laboratory. A simple rule of thumb is derived relating the shear strength of the sediment to the pullout force. Multiple APC holes at individual sites allow the consistency of the pullout measurements to be assessed. The effects of different operational procedures during APC coring are also explored. Although generally applicable, the correlation between pullout force and laboratory measurements of shear strength breaks down for some APC holes, possibly because of the disturbance of some sediment types during the APC coring process. A better understanding of the physical process of APC coring, and its effect on the properties of the sediment both inside and immediately outside the core barrel, would indicate what confidence can be put on the measurement of pullout force as a way of evaluating the in situ shear strength of deep sea sediments. 相似文献
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Shigehisa Nakamura 《Marine Geodesy》2000,23(1):55-61
Specific properties of the interannual sea level variations and annual tides in the Northwestern Pacific were studied. Several tide stations were monitored. The monthly mean sea level for the year of 1995 was analyzed at each tide station. A seismic event in 1995, some tectonic activity around the subject area, and the Kuroshio (the oceanic western boundary current) may possibly contaminate results which would have occurred from the astronomical annual tide alone. 相似文献
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