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为了更好地认识西太平洋暖池区北部卡罗琳海域沉积速率的变化,利用放射性碳测试（14C）、氧同位素及古地磁方法对采自西太平洋卡罗琳地区一根长217 cm的柱状样开展了综合年代学分析。14C数据获取了样品上部44.3 ka BP以来的年代数据,在此基础上利用氧同位素及古地磁相对强度数据建立了该柱125 cm至表层的年代框架,对应为MIS4期（约8万年）以来的沉积。进一步分析发现本柱在126～127 cm处存在明显沉积间断,虽然该处已超出14C测年范围,但古地磁测试结果表明该柱位于布容正极性时期,同时古地磁强度与氧同位素的变化关系为沉积间断以下年代数据获取提供了可信的证据,表明该阶段对应距今13万年至18万年时期。本柱沉积速率在沉积间断前后均较为一致,为1～2 cm/ka。同时对比不同方法获取的沉积速率之间差异后,发现个别层位可能由于较高的有孔虫破壳率,导致14C值存在较大偏差。 相似文献
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第四纪时期在鄂尔多斯块体上所堆积的黄土系列沉积,是为特殊气候环境所形成.其周围断陷盆地内,下部为河湖相沉积,上部为黄土类沉积、区内上新世红粘土沉积后出现的侵蚀面,是第三纪和第四纪分界界面标志.又据古地磁资料,第四纪底界时代为300万年左右. 相似文献
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周墨清 《海洋地质与第四纪地质》1995,15(1):41-56
本文通过太平洋中部５个长柱状岩心古地磁样品的测量分析，对区内早中新世以来的松散沉积层进行了磁性地层的划分对比，确定了各孔研究深度内沉积层的时代，认识到太平洋中部新世以来主要有两个沉积时期和两个沉积间断时期。第一沉积期分别到早中新世末或中中新世初停止沉积，为主沉积期，沉积了岩心的大部分。从晚上新世或第四纪初开始沉积到第四纪中晚期停止沉积的是第二沉积期，从早中新世末或中中新世初至早上新世或第四纪初为主 相似文献
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青海柴达木盆地西部上新世以来的地质环境与成盐期 总被引：5，自引：0，他引：5
对柴达木盆地西部大浪滩及察汗斯拉图地区的上新世晚期以来的沉积物及其孢粉化石的研究,结合古地磁、同位素年代测定,建立了九个孢粉带、九个植被演变期、三十次气候波动及三个成盐阶段。分析了本区主要成盐时期的古气候特征。 第四纪下限位于Ⅲ/Ⅱ孢粉带之间,对应于古地磁的M/G界面。中更新世底界位于Ⅵ/Ⅴ孢粉带之间,对应于古地磁的B/M界面。晚更新世底界位于Ⅷ/Ⅶ孢粉带之间,铀系测年为距今15—17万年。 相似文献
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通过450m长的五号桩岩芯的粒度分析、粘土矿物分析、碳酸盐分析和古地磁测年,揭示了现代黄河三角洲地区上新世晚期(约距今380×10~4a)以来,经历了一个长期稳定的沉积过程,沉积了一套以河流-湖泊相为主的粉砂质粘土、粘土质粉砂和细砂沉积;晚更新世以后,局部地区受渤海海侵影响,接受海相沉积。本区沉积动力作用很弱,沉积作用主要受区域构造运动和沉积古气侯的影响;晚更新世以前,在渤海地区的海侵期间,可能海水并未进入本区。 相似文献
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浙江宁波地区第四纪磁性地层的初步研究 总被引：1，自引：0，他引：1
本文根据宁波地区B12和LK1两孔472块古地磁样品的测定,结合微体古生物、孢粉和地层等资料,对宁波地区的第四纪磁性地层的划分与年代作一初步探讨.经分析表明,宁波地区迄今钻遇的第四系地层,在极性年表中属于73万年以来的布容正向时,未见早更新世的沉积;全新世底界以哥德堡亚时为标志,距今1.2—1.3万年;晚更新世底界应放在吉曼卡亚时为宜,距今19.8—21.5万年. 相似文献
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对东太平洋海盆 ４３０ 柱沉积物的组分、古生物、结构构造以及古地磁、铀系等进行研究后, 将沉积物进行分类、命名与分层, 并确定其年代。研究表明, 本柱由下至上的沉积物分别为含沸石粘土、深海粘土、硅质粘土和钙质粘土。该柱中存在 ４ 个沉积间断, 其中在 ３２５ ｃｍ附近层位有一厚约 １０ ｃｍ 的多金属结核层,此界面为中中新世至晚上新世的沉积间断,它在 Ｃ Ｃ区内普遍存在, 持续时间长, 分布范围广。反映此时南极底层流十分强盛, 对东太平洋 Ｃ Ｃ 区的沉积作用和多金属结核形成与发育产生重要的影响。 相似文献
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研究福建深沪湾多种相的晚更新世沉积,包括有冲洪积相的含砾砂黏土、湖相黏土、潮间带生物沉积相即大片的古牡蛎滩及滨海相河口潮滩砂黏土和风成老红砂等,研究了它们的沉积学特征和形成古环境及其可能反映的复杂的构造形变.沉积相特征表明,深沪湾地壳经历了距今约60 000 a以来早期的可能下沉(距今约28 000 a开始海浸)—距今约25 000~15 000 a的与水动型海平面上升速率大致相同的抬升(生成晚更新世古牡蛎滩)—距今约15 000~11 000 a的可能与古强地震相关的快速抬升(古牡蛎滩脱离海面形成古牡蛎滩台地,深沪湾地区生成多个陆地凹陷)—距今约11 000~7 000 a的相对稳定(凹陷内生长古森林)—距今约7 000 a的古强地震快速下沉(形成潟湖、古森林沉溺)—相对稳定—微弱抬升(又一次成陆)—距今约2 400 a的又一次古强地震快速下沉(形成海底古森林及潮间带古牡蛎滩遗迹)—相对稳定(海岸堤形成)的地壳形变及环境变迁过程. 相似文献
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台湾海峡台西盆地新生代构造事件的分析 总被引：2，自引：0，他引：2
通过不整合，地层缺失，岩浆活动，断裂活动等分析，以及与邻区构造事件进行对比，认为台西盆地新生代构造事件主要有晚白垩世晚期－古新世早期（距今约７０Ｍ－６０Ｍａ），古新世末－始新世初（距今约５４Ｍ－５１Ｍａ），始新世晚期－渐新世早期（距今约４２Ｍ－３２Ｍａ），晚中新新世－上新世初（距今约１０Ｍ－５Ｍａ）和上新世末－中更新世（跑今约２．５Ｍ－１Ｍａ）。它们在区内表理明显，依次反映了台西盆地从裂谷出现（晚 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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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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《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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Phylogenetic diversity and phenotypic characterization of cultivable bacterioplankton isolated from polar oceans 总被引：1，自引：0，他引：1
A set of 27 marine planktonic bacteria isolated from the polar regions was characterized by 16S rDNA sequencing and physiological and biochemical testing. More than half of these bacteria were positive for caseinase, gelatinase and 13-glucosidase, and could utilize glucose, maltose or malic acid as carbon source for cell growth. Twelve isolates expressed nitrate reduction activities. Except for one antarctic isolate BSwlO175 belonging to Actinobacteria phylum, these isolates were classified as γ-Proteobacteria, suggesting that γ-Proteobacteria dominated in cultivable marine bacterioplankton at both poles. Genus Pseudoalteromonas was the predominant group in the Chukchi Sea and the Bering Sea, and genus ShewaneUa dominated in cultivable bacterioplankton in the Prydz Bay. With sequence similarities above 97%, genus Psychrobacter was found at both poles. These 27 isolates were psychrotolerant, and significant 16S rDNA sequence similarities were found not only between arctic and antarctic marine bacteria （ 〉 99% ）, but also between polar marine bacteria and bacteria from other aquatic environments （ ≥ 98.8% ）, including temperate ocean, deep sea, pond and lake, suggesting that in the polar oceans less temperature-sensitive bacteria may be cosmopolitan and have a bipolar, even global, distribution at the species level. 相似文献
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The relationship between the flux of exotic benthic foraminiferal tests (i.e. tests which are supplied from open-sea sources alone) in a tidal inlet and that of bulk sediment was analysed, which can be expressed as two first-order linear equations. According to this relationship, in order to determine net sediment transport directions in the entrance, the test concentration in surficial sediments of the tidal basin can be compared against a ‘ critical level ’. The critical level is determined for the conditions that no net transport of bulk sediment is present within the entrance. If the observed concentration (averaged over the tidal basin) is higher than the simulated critical level, then the net sediment transport is directed to landward. This method is applied to the analysis of net sand transport at Christchurch Harbour, a tidal inlet system located in southern England. In this investigation, concentrations of exotic foraminiferal tests in the surficial sediments of the tidal basin and ebb tidal delta area were obtained from the analysis of sea-bed sediment samples. A series of probable critical levels were calculated based upon the data sets with regard to: (1) sediment discharge from the rivers; (2) magnitude of sediment discharge within the entrance during the ebb; (3) the test concentration outside the harbour; (4) the thickness of the moving layer; and (5) two parameters associated with dispersive processes. The results show that the concentration in the tidal basin sediment is higher than a number of simulated critical concentrations for representative cases. Consequently, the high level of the concentration of exotic benthic foraminiferal tests within the harbour should be explained as a result of landward net transport of sands within the entrance. 相似文献