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1.
越南岸外上升流区48万年来高分辨率的生源组分记录及其古海洋学意义 总被引：1，自引：1，他引：1
南海西部越南岸外MD05-2901孔沉积物分析显示,该孔覆盖氧同位素1-12期,底界年龄约为48万年。生源组分记录显示表层古生产力冰期高、间冰期低,体现间冰期海平面下降、陆源物质输入增强的影响。生产力在末次冰期达到最高,体现末次盛冰期海陆差异增强,东北风发育对生产力提高的促进作用。碳酸钙含量变化呈现冰期早期含量低、冰消期和间冰期含量高的趋势。其冰消期的高值在MIS1/2、MIS3/4和MIS5/6分界处,与浮游有孔虫碳同位素低值对应,揭示该地区的碳酸钙沉积旋回是“稀释旋回”。同时碳酸钙含量变化领先于同一地区浮游有孔虫氧同位素的变化,证明低纬海区碳酸钙泵作用对大气二氧化碳浓度和温度有影响。滤波分析结果显示碳同位素存在23 ka的岁差周期和偏心率长周期,生源组分的含量变化显示出典型的岁差周期,体现南海季风环流的轨道响应,证明低纬热带过程是调节气候变化的重要因素。 相似文献
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南海南部NS93-5柱样揭示的晚第四纪以来的古海洋学特征 总被引：3，自引：0，他引：3
由南海南部海区NS93 - 5柱样的浮游有孔虫氧同位素地层学和浮游有孔虫分析结果获得的古环境参数 ,揭示了距今 1 90ka以来南部海区受西太平洋热带水的影响 ,以及南沙海区表层水和苏禄海变性水的变化历史 ;在末次盛冰期碳酸盐含量较低 ,但是碳酸盐含量的最低值出现在氧同位素 4期 ;表层水体的含氧量呈现为间冰期大于冰期 ,而古生产力的变化则为冰期大于间冰期 ;依据氧同位素和浮游有孔虫特征分析结果 ,建立了南部海区距今 1 90ka以来的古气候演变序列。 相似文献
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对南海南部ODP1143站氧同位素11-5e期大约2ka分辨率的粉红色Globigerinoides ruber进行分析,发现其冰期／间冰期旋回与代表全球冰量的底栖有孔虫氧同位素(δ^18O)的变化相反,即在间冰期时含量低,而冰期时高,与其他海区的记录相反。海水表层温度和温跃层深度转换函数结果以及碎壳率的变化显示,在一定的温度背景下,温跃层深度的变化可能是控制粉红色G．ruber冰期旋回的主要因素,而这段时期南海南部溶解作用的影响则不明显。 相似文献
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通过对南海北部陆坡KNG5孔沉积物粒度、粘土矿物和14C年龄的综合分析, 探讨了南海北部陆坡的沉积物来源及其控制因素。物源分析表明, KNG5孔17.5-12.5ka BP的沉积物主要来源于珠江, 12.5ka BP 时粘土矿物组合突然发生改变, 并且自12.5ka BP以后, 高岭石含量总体稳定, 说明12.5ka BP时海平面已上升到相当的高度, 并且可能当时南海的现代环流系统已开始形成, 西行的广东沿岸流导致向外扩散的珠江物质减少, 由于受北太平洋深层水(NPDW)和黑潮(KC)南海分支的作用, 台湾成为此时沉积物的主要贡献者。KNG5孔17.5-11ka BP时期的粘土矿物和粒度变化主要受控于海平面和洋流系统的变化。全新世早期(11.0-8ka BP)平均粒径达到最细和1-2.2m 粒级含量达到最高值可能是强盛的夏季风作用的结果。全新世中晚期(8—0ka BP) 1-2.2?m组分含量的减少是8ka BP以来东亚夏季风减弱的具体体现, 1-2.2m 粒级含量指示的东亚夏季风变化能和北半球其它季风指标能很好地对应起来, 说明这次季风减弱是北半球各个季风系统的共同现象。 相似文献
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南海北部中更新世0.78～1.0 Ma期间的陆源碎屑粒度记录 总被引：2，自引：0，他引：2
南海北部陆坡大洋钻探计划(ODP)1144站的高速堆积体为高分辨率的古环境研究提供了良好的材料。通过分析1144站陆源碎屑的粒径分布,高分辨率地(200a)研究了中更新世气候转型期(0.78～1.0Ma)东亚夏季风演变在南海北部的记录。结果显示,陆源碎屑的粒径比值(3.5～8.2μm)/(9～23μm)可以作为东亚夏季风演化的替代指标,高值代表强盛的夏季风。这个比值指示了夏季风在920ka时突然增强,表明中更新世转型以夏季风突然增强为起点,此后夏季风处于不断加强和减弱的循环状态,说明了中更新世气候转型是一个渐变的过程。东亚夏季风演化的强弱与北半球夏季日射量基本呈线性关系,显示东亚季风演化的天文驱动机制。频谱分析发现,夏季风演化存在3.3ka和1.2ka左右的千年尺度周期,且在转型前后千年尺度周期也发生变化,说明中更新世的气候转型不仅表现在轨道尺度的气候周期变化上,也体现在千年尺度气候波动的特征变化上。 相似文献
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西太平洋暖池北部15万年以来的碳同位素低值事件 总被引：1，自引：1，他引：0
对取自西太平洋暖池北部的MD06-3052孔的浮游有孔虫表层种Globigerinoides ruber进行了稳定氧碳同位素测试与分析,在所建立的年龄模式基础上,揭示了该孔150 ka以来氧碳同位素的变化特征及其碳同位素低值事件的时间。结果表明,150 ka以来碳同位素总体上显示出逐渐变重的趋势,其变化不同于氧同位素,并未表现出冰期-间冰期尺度的变化特征,且全新世和末次间冰期碳同位素差异较大。在所识别出的6次碳同位素的低值事件中,除倒数第二次冰消期与岁差低值有相位差以外,其余均与岁差低值都有很好的对应。幅度较大的3次发生于冷期/暖期的过渡期,其中末次冰消期的碳同位素记录受到浊流的侵蚀作用,有部分缺失;该孔与其他海区记录的相似性进一步证实了3次冰消期的δ13C低值事件的普遍性。 相似文献
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南沙南部近30ka来的古海洋学记录 总被引：3，自引：1，他引：3
南海南部17962柱状样(7°11′N、112°5′E,柱长8 m,水深1 968 m)中近30 ka来的沉积物堆积速率计算结果显示,该孔冰期平均堆积速率为全新世的3倍多.其变化与冰期时海平面下降、地表径流所携陆源物质增多、全新世时海平面的回升以及陆源物质的提前卸载有关.浮游有孔虫氧同位素测定结果表明,该孔的浮游有孔虫的氧同位素冰期/全新世差值高于南海的平均值,更大于开放性大洋赤道西太平洋低纬度区的平均值.CaCO3变化则受陆源物质的"稀释作用"控制,而溶解作用对其影响并不太显著. 相似文献
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对南海北部89PC柱状样进行了浮游有孔虫定量统计分析、氧碳同位素测试、碳酸钙含量分析和AMS14C测年,并采用古生态转换函数计算了表层海水古温度和温跃层深度,揭示了该海区约127 ka以来的古海洋学特征。温跃层转换函数计算的温跃层深度结果表明,在MIS5-MIS4期,温跃层深度没有大的变化,在MIS3-MIS1期,温跃层的深度逐渐变深。古温度转换函数计算的古温度结果表明,夏季温度的变化范围为27.9~29.3℃,变化幅度为1.4℃,冬季温度变化范围为20.6~26.3℃,变化幅度为5.7℃。与南海南部的冬夏古水温资料进行对比,南海南部的温度比南海北部的温度要高,这种差异在冬季时表现更为突出,且在冰期时南海南部和北部的温度差异梯度进一步增大,指示了冰期时冬季风更加强盛。 相似文献
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《海洋地质与第四纪地质》2010,(4)
对南海西沙群岛附近陆坡、南海南部陆坡以及东沙群岛附近陆坡晚第四纪磁化率变化特征进行了综合对比,并初步分析了磁化率与碳酸钙百分含量之间的关系。就磁化率变化特征而言,西沙群岛附近陆坡和南海南部陆坡可归为一个单元,东沙群岛附近陆坡划为另一单元,其中,前一单元晚第四纪磁化率曲线的共性表现为深海氧同位素期次的奇数期向偶数期过渡时期以磁化率峰值为特点,偶数期向奇数期过渡时期以磁化率谷值为特点;后一单元晚第四纪磁化率曲线的共性表现为磁化率曲线大致平行于有孔虫氧同位素曲线。上述两个单元内的磁化率曲线共性都具有地层学意义,但这两个单元内部某些部位的晚第四纪磁化率变化具有地方局限性,不宜当作大范围地层对比的工具。南海陆坡磁化率曲线和碳酸钙百分含量曲线的关系存在镜像和平行两大基本类型,但这两种对应关系未必意味着磁化率和碳酸钙百分含量之间存在着直接的因果联系。南海陆坡磁化率变化的原因很可能与冰期旋回中南海陆源物质通量的变化密切相关,另外,局部海域磁化率还可能严重受沉积物早期成岩作用的影响。 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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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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The effect of different fixation and storage protocols on the flow cytometric (FCM) simultaneous analysis of bacterioplankton and phytoplankton in coastal seawater samples (Mediterranean coastal lagoons) was investigated. FCM measurements (cell number, fluorescence and scatter characteristics) were obtained through DAPI staining. Three fixatives [glutaraldehyde (GA), formaldehyde (FA) and paraformaldehyde (PFA)] and two storage (3 months duration) methods (5 °C and −196 °C) were tested. Two dominant populations were detected in studied samples: bacteria and eukaryotic picophytoplankton. Adding fixatives (2% final concentration) appears necessary to obtain FCM exhaustive counts of all the bacteria and phytoplanktonic cells. This was related to the permeation effect of fixatives which allowed a better DAPI staining of the cells. Maximum fluorescence, i.e. optimal staining of the cells was obtained with FA or PFA, and significant lower fluorescences with GA. Fixed samples stored at 5 °C induced rapid cell loss. Only storage in liquid nitrogen of samples fixed with FA or PFA, allows mid-term (≥4 months) preservation of bacteria or picophytoplankton cell numbers, and limited evolution of DAPI-induced fluorescence and scatter characteristics. 相似文献
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Coastal inundation associated with extreme sea levels is the main factor which leads to the loss of life and property whenever a severe tropical cyclonic storm hits the Indian coasts. The Andhra and Orissa coasts are most vulnerable for coastal inundation due to extreme rise in sea levels associated with tropical cyclones. Loss of life may be minimized if extreme sea levels and associated coastal flooding is predicted well in advance. Keeping this in view, location specific coastal inundation models are developed and applied for the Andhra and Orissa coasts of India. Several numerical experiments are carried out using the data of past severe cyclones that struck these regions. The simulated inland inundation distances are found to be in general agreement with the reported flooding. 相似文献
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《海洋学报(英文版)》2014,(9):F0003-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
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Hoi-Soo Jung Kap-Sik Jeong Yong-Shik Chu Sung-Hyun Park Ki-Hyune Kim 《Marine Georesources & Geotechnology》2001,19(3):181-195
Grain size and water content in box-core sediments from the Clarion-Clipperton fracture zone (C-C zone) in the northeast equatorial Pacific were analyzed in detail to understand the downcore variations across a hiatus between Quaternary and Tertiary layers. Grain-size distributions in the topmost core sediments show two modes: a coarse mode (peaked at 50 μm) and a fine mode (at 2-25 μm). The coarse mode disappears gradually with depth accompanied by the dissolution of siliceous fossil tests, whereas the fine mode coarsens due to the formation of authigenic minerals. Water content increases abruptly across a color boundary between an upper pale brown layer and a lower dark brown layer that is the hiatus between Quaternary and Tertiary layers. Abundant smectites and microvoid molds, which are created by the prolonged fossil dissolution in the underlying sediment, are attributed for the abrupt downcore variation of water content. Overall variations in grain size and water content in the topmost core sediments in the western C-C zone are possibly constrained by the dissolution of biogenic siliceous fossils. Variations in geotechnical properties related to these changes must be considered in the design of nodule collectors. 相似文献
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Shigehisa Nakamura 《Marine Geodesy》2001,24(1):27-33
This article concerns an interrelation between the sea levels and the western boundary flow near a tectonic boundary in a local zone in the Northwestern Pacific. In this zone, sea level variations at stations located on the coast facing the Pacific are studied to find the interrelation between variations of the Kurosio flow as an index of the distance of the flow axis off a specific coast. The result is discussed after data processing of the monthly means of the sea levels, and a notice is taken of variations caused by active crustal upheavals during a seismic event, a local earthquake. 相似文献
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This study tests the hypothesis that the in situ void ratio of surficial marine sediments may be predicted from shear wave velocity-depth data with a reliability equal to that of other methods currently available. Shear wave velocity is fundamentally controlled by the number of grain-to-grain contacts per unit volume of material and by the effective stress across those contacts. In this study, three previously established empirical formulae are used to predict void ratio from velocity-depth data. Field data were acquired along a transect off the northern Californian coast across which water depth increased from 35 to 70 m and seafloor sediment type varied from sand to silty-sand, respectively. A towed seafloor sled device was used to collect shear wave refraction data, and a marked, systematic decrease in velocity was observed along the line, ranging from 35-70 m/s for the coarse, near-shore material to 25-40 m/s for the finer, offshore deposits. Void ratios predicted from these velocities were compared with data measured directly from box-core samples. Of the formulae used for prediction, two agree remarkably well with the control data. Both predicted and control values increase from 0.6-0.8 for the sandy material to 1.1-1.5 for the silty-sand. Thus, this study does not disprove the hypothesis set and demonstrates the potential of field shear wave velocity-depth data as a means of delineating spatial variation in void ratio for surficial marine sediments in a remote, nondestructive manner. 相似文献
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Particulate samples were collected from the Changjiang river system during a flood period, in May 1997, and POC, stable isotope and lipids associated with particles were examined. Results showed the decrease (0.84% ～ 1.88%) of organic carbon content from the upper reaches to the estuary.δ13C values of particulate organic carbon was in the range of -24.9×10-3 to -26.6×10-3, which were close to the isotopic signature of continental C3 vegetation. Total particulate n-alkanes concentrations varied from 1.4 to 10.1μg/dm3,or from 23.7 to 107μg/g of total suspended matter. Fatty acids were present in all the samples, from 1.4 to 5.4μg/dm3, with saturated and unsaturated straight-chain and branched compounds in the carbon number range from C12 to C30. Both δ13C and the ratio of carbon content to nitrogen content indicate the predominance of terrestrial inputs (soil organic matter) among the particles. The biomarker approach has been used to identify the relative portion of terrigenous and autochthonous fraction in the particulate samples. The distribution of fatty acids suggests a striking phytoplanktonic and microbial signal in most particle samples. The terrestrial alkanes are used to estimate the contribution of terrestrial inputs along the mainstream. 相似文献