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1.
《海洋地质与第四纪地质》2010,(6)
粒度测试表明九江红土具风成特征。粉砂(4～63μm)为优势粒级,含量为66.20%～74.02%,富集风尘粒组。选择敏感粒组15～30μm作为气候代用指标,根据ESR测年和粒度年龄模型,建立JL剖面时间标尺,结果表明其沉积时代为2098.4～233.2kaBP,跨早、中更新世。下段网纹红土的沉积年龄为2098.4～441.5kaBP,上段棕黄色土的沉积时代为441.5～233.2kaBP。基于3PBase软件对234～2084kaBP期间气候周期的频谱分析,九江JL红土剖面记录了准100ka、准41ka和准30ka的地球轨道要素变化周期,并在734～784kaBP期间,气候周期发生了转型,由之前的准41和准30ka地轴倾斜率周期变成之后的准100ka地球轨道偏心率周期,这一信号响应了全球范围内中更新世气候转型事件。谱密度分析还表明剖面气候周期具复杂性,可能与东亚季风的非线性反馈机制有关。 相似文献
2.
我国南方红土岩石磁学特征及其磁化率增强机制 总被引：1，自引：0，他引：1
《海洋地质与第四纪地质》2015,(4)
我国南方第四纪红土是研究古环境变化的重要载体,主要由均质红土和网纹红土两大不同类型的沉积层组成。运用岩石磁学、漫反射光谱和粒度相结合的方法,分别对我国南方长沙(CS)、岳阳(HN)、南昌(NC)以及新余(XY)典型红土剖面的均质层和网纹层进行了详细的对比分析,结果表明网纹红土层2μm的黏粒含量较多,网纹红土层形成时期气候更加温暖湿润,成土作用高于上覆均质红土层。磁铁矿、磁赤铁矿、赤铁矿和针铁矿都是均质红土层和网纹红土层磁性矿物的主要载体。其中,网纹红土层的亚铁磁性矿物低于均质红土层,主要以较粗的假单畴PSD和多畴MD存在,反铁磁性矿物以赤铁矿为主;而上覆均质红土层却以较多的SSD磁赤铁矿为主。网纹红土层可见大量黑褐色铁锰胶膜和铁锰结核分布,这是由于沉积后土壤长期处于高温高湿的还原环境中,强磁性矿物如细粒磁铁矿、磁赤铁矿等部分被溶解转化为弱磁性矿物(如赤铁矿和针铁矿,主要是赤铁矿),这种磁性矿物的转化可能导致了成土作用强的网纹红土层较粗磁性颗粒的增加,而超顺磁亚铁磁性矿物含量的减少以及磁化率的降低。 相似文献
3.
长江口及其邻近海域表层沉积物粒度划分及变化规律研究 总被引：2，自引：0，他引：2
对长江口及其邻近海域30个站位的表层沉积物粒度进行了粒级划分,在此基础上探讨了各粒级的变化规律。结果表明研究区表层沉积物最高含量粒级——粉砂(粒径4-63μm,含量大于50%)并非组成沉积物的主体粒级,<16μm的细粉砂及黏土粒级才是研究区的主体粒级,含量在50%-80%之间,能代表粒径频率分布的中心趋向和平均搬运动能情况。16μm是研究区沉积物粒度性质的一个分界点。通过对表层沉积物粒级的研究还发现研究区沉积物粒度粒级含量变化具有明显的规律性:4-8μm,8-16μm细粉砂粒级百分含量的变化规律与<1μm,1-2μm,2-4μm粒级(细分的黏土粒级)完全一致,与>16μm的各粒级之间不相关或呈强的负相关关系;16-32μm、32-63μm粗粉砂粒级含量的变化规律与63-125μm,125-250μm,>250μm粒级(细分的砂粒级)的变化规律呈弱相关或弱负相关关系,与<16μm的各粒级的变化规律不相关。对沉积物粒度的不同组分研究有助于对沉积动力环境和元素的“粒度效应”等问题进行深入探讨。 相似文献
4.
沉积物的粒度特征受控于沉积环境的变化,是沉积学研究中的重要物理指标之一。沉积物中不同粒级的颗粒物记载了详细的物源信息及水动力活动等特征,因此,有效并快速地分离不同粒级的沉积物对古环境演化研究十分重要。沉降法是沉积物粒度分级最基本的方法,然而用沉降法对细颗粒物质含量较多的海洋沉积物进行粒度分级时,耗时久,分离效率低。离心法可以加速细颗粒物质的沉降速度,提高分离效率。因此,选择离心法对东海内陆架泥质沉积区的27个表层沉积物进行粒度分级(2μm,2～10μm,10～63μm,63μm)。显微镜观察结果显示不同粒级的颗粒间基本没有混染,表明离心法的分离效果较好。样品回收率在94%左右,最高可达97%以上。样品的损失量与细颗粒含量呈正相关,即细颗粒含量越多,损失量越大。与激光粒度仪测试结果对比发现,激光粒度仪对10μm颗粒物区分度较差,低估2μm颗粒物含量,高估2～10μm颗粒物含量。本研究表明离心法可以高效地对海洋沉积物进行粒度分级。 相似文献
5.
通过对“太阳号”115航次18268-2孔陆源碎屑高分辨率沉积粒度分析,获取了大约2.5万年以来巽他陆坡下部沉积物粒度分布特征的详细记录。结果显示,该孔陆源碎屑颗粒较细,粒径在2~10μm之间的含量最高,几乎不含大于63μm的颗粒。沉积物粒度分布的均值和中值与粒径在10~63μm之间的百分含量相关性较好,说明古水流速度决定着沉积物粒度分布在短时间尺度上的变化。14.6~14.3 kaBP期间海平面迅速上升造成海岸线后退数百千米,使本地区沉积物供应产生了明显的变化,从而造成所有统计参数及各组分相对百分含量在15 kaBP前后均发生了明显变化,这说明沉积物供应控制着沉积物粒度分布较长时间尺度上的变化。 相似文献
6.
通过对铜川剖面黄土-古土壤沉积粒度的组成和变化特征及磁化率值进行分析,探讨了该地区11.4～1.5 kaBP期间的古气候变化特征。结果表明:(1)铜川剖面黄土-古土壤沉积以粉砂粒(4～63μm)为主,黏粒(4μm)次之,砂粒(63μm)含量最低。(2)粒度和磁化率值在不同地层单元呈规律性变化:粉砂粒和砂粒在黄土层中较高,古土壤层中较低;黏粒和磁化率值在黄土层中较低,古土壤层中较高。(3)粉砂粒、黏粒和磁化率值的变化情况较好地记录了铜川地区11.4～1.5 kaBP期间的气候变化特征,可以将该地区的气候变化划分为4个阶段:11.4～10.2 kaBP寒冷干燥期,10.2～9.1 kaBP略温偏干期,9.1～4.4 kaBP温暖湿润期,4.4～1.5 kaBP较冷干期。 相似文献
7.
南海南部末次冰期以来的沉积物特点及其古环境意义 总被引：3，自引：2，他引：3
对南海南部接近湄公河三角洲中陆坡上的MD01 2392站样品进行了地球化学和粒度分析,揭示出该站位上部12 8m地层包含了完整的末次冰期约7万年以来的沉积旋回。其MIS4期以来的沉积速率是南海南部已知站位柱状样中最高的,呈现冰期高而间冰期低的特征;并发现沉积物中Ti、Si、Fe和Al等元素含量在冰期时高,推测与低海面时期具较高的陆源物质输入有关。元素Sr、Ba、Ca的含量分布与CaCO3的相似,冰期低、间冰期和全新世高;推测冰期低值是陆源和非CaCO3物质稀释作用的结果。粒度分析表明粉砂(2～63μm)是该站陆源物质的主要成分,粗组分(>63μm)主要出现在MIS2的早、晚期,指示有浊流沉积存在。 相似文献
8.
《海洋地质与第四纪地质》2016,(2)
设计了针对红土的两种粒度分析方法,对比分析了铁锰结核对红土粒度分析结果的影响以及加入HCl对铁锰结核与红土粒度测试的影响。结果表明:(1)细粒铁锰结核对粒度测试结果有较大影响,特别是粗粒含量的增加。而盐酸可以有效地与细粒铁锰结核反应,使得粒度测试结果更接近真实值。因此,对于铁锰结核发育的红土层,若需通过粒度来分析其沉积动力特征,其粒度测试的前处理过程加入盐酸是非常有必要的。(2)盐酸的加入对红土中4μm的黏土粒组有较大影响,这可能是盐酸与黏土矿物发生了化学反应,使得黏土粒组的相对含量减少。因此,对于铁锰结核发育的红土层,若需要通过粒度分析其风化过程,其前处理应当慎重选择是否加入盐酸。 相似文献
9.
巴丹吉林沙漠地层序列的粒度分布及其组分成因分析 总被引：3，自引：0，他引：3
对巴丹吉林沙漠腹地WEDP02孔310.45m的岩心进行了高分辨率的激光粒度测量,运用Normal和Weibull函数对全孔的粒度分布进行了拟合和组分分离,在结合野外沉积相判断的基础上,将组分的粒径-频率、含量-频率变化作为组分成因分析的依据,系统分析了WEDP02孔沉积序列的粒度组分的成因。结果表明:WEDP02孔沉积物主要以风成砂、湖泊-风成砂混合沉积、冲洪积-风成砂混合沉积为主。风成沉积物中,超细粒成壤、高空远源粉尘、低空近源粉尘、风成砂与风成粗砂组分的粒径界线为2、12、105和270μm,粉尘与风成砂组分的比例平均值为20%/80%,在粒度组分的粒径-含量投影图中占据右上角部分;湖相沉积物中超细粒化学、悬移及风成砂组分的粒径界线为4、45、150~230μm,湖相悬移组分含量大于35%,同时可含有风成组分和湖相砂,在粒度组分的粒径-含量投影图中占据细粒下部分;冲洪积超细粒化学、悬移黏土、悬移粉砂、风成砂、冲洪积砂的粒径界线为2、12、80、150~200和300μm。这些特征反映了巴丹吉林沙漠不同沉积物的沉积学特征,是沉积物成因分析的粒度依据。 相似文献
10.
《中国海洋大学学报(自然科学版)》2017,(6)
本文通过对位于莱州湾南侧、潍坊港东侧近岸海域300cm长的WF01钻孔进行磁化率和粒度测试,结合测年数据,分析了研究区海域沉积速率、沉积物粒度和磁化率的演化特征,探讨了不同沉积物粒度组分与磁化率变化的相关关系。结果表明:WF01孔0~300cm沉积物可分为四段,分别体现了不同时期研究区沉积环境的变化。WF01孔以218cm为界,上段与下段沉积物磁化率与各粒组百分含量的相关关系基本呈相反趋势。上段沉积物磁化率与63μm以下各组分的百分含量呈负相关关系,与大于63μm粗颗粒的百分含量呈正相关;下段沉积物磁化率值与小于32μm各组分的百分含量呈正相关关系,而与大于32μm的颗粒组分含量呈负相关关系。这种相关性的差异,可以从很大程度上指示研究区上下两段沉积物物质来源的不同,而造成这种物源差异的原因很可能是1855年黄河从苏北改道进入渤海,巨量黄河泥沙在渤海沉积、扩散造成的。 相似文献
11.
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
12.
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
13.
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
14.
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
15.
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
16.
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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《海洋学报(英文版)》2014,(11):161-F0003
<正>Acta Oceanologica Sinica(AOS)is a comprehensive academic journal edited by the Editorial Committee of Acta Oceanologica Sinica and is designed to provide a forum for important research papers of the marine scientific community which reflect the information on a worldwide basis.The journal publishes scholarly papers on marine science and technology,including physics,chemistry,biology, 相似文献