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1.
为了探索和揭示2.5 MaBP前后东亚季风演变历史及植被演替对气候演化的响应,对南海南部大洋钻探ODP1143站(9°22'N、113°17'E)深海柱状样的上部135～95 m(3.0～2.0 MaBP)共146个孢粉样品进行了分析研究,时间分辨率为7 ka/样,孢粉谱显示沉积率变化显著,以2.6 MaBP为界可明显分为两个阶段,与前一阶段3.0～2.6 MaBP相比,2.6～2.0 MaBP时段各类型花粉及孢子沉积率均有显著提高.该结果表明2.6 MaBP南海海平面有显著下降,可与北半球冰盖形成、东亚季风增强相对应.2.6 MaBP以后,各类型孢粉沉积率高低变化揭示南海海平面有多次上升和下降,代表了多次冰期-间冰期旋回.该结果与深海氧同位素分期相对应.频谱分析表明3.0～2.0 MaBP存在0.1 Ma(偏心率)和46.9 ka(斜率)的周期. 相似文献
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为了探索和揭示2.5MaBP前后东亚季风演变历史及植被演替对气候演化的响应,对南海南部大洋钻探ODP1143站(9°22'N、113°17'E)深海柱状样的上部135～95m(3.0～2.0MaBP)共146个孢粉样品进行了分析研究,时间分辨率为7ka/样,孢粉谱显示沉积率变化显著,以2.6MaBP为界可明显分为两个阶段,与前一阶段3.0～2.6MaBP相比,2.6～2.0MaBP时段各类型花粉及孢子沉积率均有显著提高。该结果表明2.6MaBP南海海平面有显著下降,可与北半球冰盖形成、东亚季风增强相对应。2.6MaBP以后,各类型孢粉沉积率高低变化揭示南海海平面有多次上升和下降,代表了多次冰期-间冰期旋回。该结果与深海氧同位素分期相对应。频谱分析表明3.0～2.0MaBP存在0.1Ma(偏心率)和46.9ka(斜率)的周期。 相似文献
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山西榆社-太谷盆地上新世中晚期的植被与环境 总被引：5，自引：0，他引：5
山西中、东部的榆社、太谷盆地发育了良好的上新世河湖相地层，其丰富的植物、鱼类和哺乳类化石为我们提供了一个古植被和古环境研究的理想场所。根据榆社盆地磁笥年表以及化石组合特征，榆社、太谷盆地约为5．5MaBP以来的套沉积、榆社张村组与太谷小白组的沉积时代相当，大约形成于3．5－2．3MaBP。从大约4．4MaBP开始，较高含量的云杉、冷杉花粉显示研究区已有暗针叶林生长，从3．5MaBP开始，暗针叶林有了较大的发展，存在大面积的暗针叶林纯林。大致从上新世中期的4．4MaBP开始，气候已经开始变冷，并有较明显的干湿波动，蒿、藜为主的干草原大约从2．3MaBP开始繁盛，表明研究区转变为干冷气候。 相似文献
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东昆仑阿拉克湖盆地1.85～1.58 MaBP间植被演替及高原隆升启示 总被引：2，自引：0，他引：2
东昆仑阿拉克湖盆地1．85～1．58MaBP间植被演替顺序为灌木及草本植物为主的疏林草原型一乔木为主的林下草原型一针叶林森林型一阔叶林为主的林下草原型,反映了温凉为主的干湿交替一温和为主的干湿交替一寒冷略湿一温暖潮湿的气候湿度。孢粉植物群总体为以灌木及草本植物为主的疏林草原型,气候以温凉为主,其中1．63～1．62MaBP出现具亚寒带气候特征的针叶林植物群。与3．4Ma青藏运动前后的干旱、温暖的气候背景相比有明显差异,说明东昆仑地区经过青藏运动A、B幕后高原隆升已达到或超过水汽凝结高度。临夏盆地和阿拉克湖盆地在1．85～1．58MaBP间的植被类型和植被演替阶段非常相似,特别是1．60MaBP开始同时出现喜暖阔叶植物,说明当时两盆地应处于同一气候带上,两者海拔高程应相差不大。但现代临夏盆地海拔高度为2300m左右,阿拉克湖盆地海拔高度为4200m左右,两地的现代气候与植被类型有明显差异。说明1．58MaBP以后青藏高原东北部存在重大高原(差异)隆升事件,使两地的高程和气候差异加大。 相似文献
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潮汕平原全新世孢粉分析及古环境探讨 总被引：8，自引：0，他引：8
本文根据潮汕平原多个钻孔的孢粉分析结果,探讨了全新世以来的植被和气候演替以及沉积环境变迁。结论是:该区一万年来的气候波动小,地带性植被变化不大,海滩植被的消长则与沉积环境的改变密切相关。 相似文献
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气候转型与早期人类迁徙 总被引：4，自引：0，他引：4
目前的旧石器考古证据表明，更新世早期可能发生了两次人类迁徙浪潮，时间分别在1.8-1.6MaBP和1.0MaBP左右，第一阶段，古人类演化为直立人并开始走出非洲、迁徙至其它中低纬度的热带－亚热带地区；第二阶段，直立人开始占据中高纬度的温带和干旱－半干旱地区。这两个阶段也是第四纪气候发生转型、环境产生重大调整的时期。二者在发生时间上的一致性揭示了它们之间的内在联系，推测气候转型时期环境转变是这两次人类迁徙浪潮的主要驱动力。 相似文献
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黄土高原西安地区全新世的植被与气候环境 总被引：7，自引：1，他引：6
对黄土高原中部南侧西安一带进行采样及孢粉分析,初步探讨和证实了一万年来西安地区植被的发育演替,详细地论证了该地区的古气候环境以及植被、气候和环境在时间上的演化规律和在空间上的差异,总结了早、中、晚全新世在该区发育的植被及其所代表的气候环境。根据西安蓝田、半坡两个剖面各17个样品的分析,将孢粉图式分为Ⅰ、Ⅱ、Ⅲ带,分别代表全新世早、中、晚3个时期的孢粉带。蓝田剖面显示：Ⅰ带为蒿属优势带;Ⅱ带为栎-榛-榆增长带及蒿-环纹藻优势带→栎-鹅耳枥-菊增长带;Ⅲ带为松-菊-藜-中华卷柏增长带。研究认为：早全新世植被为疏林草原,气候较冷较干;中全新世植被为温带落叶阔叶林为主的森林草原并掺杂少量亚热带植物,气候温暖湿润;晚全新世植被为以松、篙为主的森林草原,气候转向温凉干旱。 相似文献
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西藏扎布耶湖地区三万年以来的花粉记录 总被引：5，自引：0，他引：5
通过对藏北高原扎布耶湖ＺＫ２钻孔沉积物的花粉记录，揭示了该地区三万年以来植被和气候演变历史。３７３００－３６０００ａＢ．Ｐ．为森林草原植被，气候温湿，淡水湖时期；约３６０００－３１７００ａＢ．Ｐ．灌丛草原植物，气候冷干，湖水出现短暂咸化，３１７００－２０８００ａＢ．Ｐ．森林草原植被，气候温暖湿润，湖面扩大，湖水加深时期，２０８００－１４４００ａＢ．Ｐ．荒漠植被，气候冷干，湖水咸化，湖面开始缩小，初 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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《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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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
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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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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