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1.
内蒙古黄旗海湖泊沉积物δ13Corg记录的环境演变信息 总被引：3，自引：0，他引：3
处于高纬度和高海拔地区的内蒙古黄旗海湖泊沉积物δ^13Corg变化反映了气候环境的变化.特殊的自然环境条件造成黄旗海湖泊沉积物δ^13Corg负段对应暖湿环境,偏正段对应冷干环境.自8.2 kaBP开始,δ^13Corg显著降低,表明本区气候转暖;8.2～4.0 kaBP是全新世大暖期,这一时期黄旗海为高湖面,在7.8 kaBP左右本区气候最为暖湿.4.0～2.2 kaBP,δ^13Corg明显偏正,指示气候变为冷干,全新世大暖期结束.在研究时段内δ^13Corg相对于-23.5‰均值的正负偏移主要反映了湖泊有机质生产率和保存条件的变化.这种变化与当时的气候,尤其是湖泊水位的波动有直接关系. 相似文献
2.
内蒙高原腾格淖尔中全新世湖泊干旱环境的粒度和元素记录 总被引：2，自引：0，他引：2
对内蒙古高原腾格淖尔湖泊约400cm剖面沉积物的粒度、碳酸盐和TOC含量以及元素地球化学特征进行分析,利用Mg/Ca、CEC、Rb/Sr、CIA、古气候指数C等的古气候古环境指示意义,结合3个AMS 14 C年代结果,利用该区域湖泊"碳库效应"研究的基础进行年代校正,分析了腾格淖尔大约9 000cal.aBP以来古环境演变过程。研究发现腾格淖尔全新世早—中期(约9 000～4 500cal.aBP)气候暖干,有效湿度小,而湖泊为高湖面,最高湖面在约8 000～6 200cal.aBP期间;湖泊的高水位主要是继承了早全新世夏季风增强形成的扩张湖泊;3 000～4 500cal.aBP以来气候冷干,有效湿度稍有增加,湖面在降水持续减少情况下逐渐收缩干涸。 相似文献
3.
南疆博斯腾湖近12.0kaB.P.以来古气候与古水文状况的变化 总被引：6，自引：0，他引：6
对南疆博斯腾湖相沉积物多手段的综合研究，揭示了近12．0KaB.P，以来古气候与古水文状况的变化与特征。结果表明，其气候的演化特征具有明显的西风型环境演变特征。研究还发现气候120ka、10.0ka、4.0ka和1.5kaB.P.存在显著的阶梯式增暖变干特征，其中暖峰主要出现于11．5－11．0ka、9.4ka、7.5-7.0ka、6.5-6.0ka、3.0ka和2.0kaB.P.,气候特征以干暖为主，湖泊水文特征总体表现为盐度增加、水位下降、湖面缩小；而冷峰主要出现于11．0－10．0ka、8．8ka5．0－4．5ka和1．5kaB.P.,此时湖泊膨胀淡化，湖面上升。在7．0－5．0kaB.P.期间出现的相对暖湿环境特征可能是全新世大暖期最盛期暖湿气候特征的反映，可能与此时西南夏季风势力增强有关，湖泊水文状况明显变好。 相似文献
4.
新疆艾比湖全新世以来的环境变迁与古气候 总被引：10，自引：0，他引：10
于1990，1991年夏对新疆艾比湖湖盆地区进行调查，运用孢粉、元素地球化学、碳酸盐含量以及测年分析，对其沉积物进行研究，重建了湖区全新世古气候的演化序列。结果表明，10．2－8．0kaB．P，气候温凉偏干；8．0－3．5kaB.P，气候以温湿为主，其中7．3－6．4kaB．P．为相对稳定暖湿期；3.5kaB．P.至今，以温干为主，气候与现代相似。随着湖面波动，艾比湖保存有全新世3个不同时期高潮面遗迹，并应用水热平衡模型，对各个高潮面期的古降水量进行计算，全新世暖湿期的降水量比现今高出1／4以上，超过300mm／a，这时期湖面扩大了近3倍。 相似文献
5.
腾格里沙漠西北缘湖泊沉积记录的全新世中期气候环境 总被引：4，自引：0，他引：4
通过腾格里沙漠西北缘青土湖沉积物粒度、有机碳、碳酸盐、碳氮比和有机质稳定同位素等多项沉积学气候代用指标及精确定年的综合分析,建立了该区域全新世中期9.0~3.0 cal.kaBP的古气候演化序列。结果表明,9~7.8 cal.kaBP期间,区域的水分条件和温度逐渐上升,植被状况好转,此阶段属于全新世早期向全新世暖湿期转变的过程;而在7.8~7.5 cal.kaBP期间出现了显著的百年尺度的干旱事件,沉积物主要以砂质沉积为主,此时湖泊生产力显著下降;全新世期间最为暖湿的气候适宜期出现在7.5~5.0 cal.kaBP;5.0 cal.kaBP以来,该区域出现了较为明显的干旱化趋势。 相似文献
6.
云南中甸纳帕海湖泊记录指示的57ka环境演化 总被引：4，自引：1，他引：4
根据沉积环境，总有机碳，氢指数，有机碳同位素，磁化率和粒度等替代性指标以及和陆地，深海气候记录的对比，重建了纳帕海57kaBP以来的湖面变化和主要气候演化阶段，57-32kaBP主要为低湖面和频繁的湖面波动，与气候的暖偏干/凉偏湿交替有关。32-15kaBP湖面大幅度上升，出现相对高湖面，气温下降，有效湿度增加，全新世湖盆的萎缩与持续的暖偏干气候有关，这种冷湿-暖干气候与滇西北特殊的地形地貌造成大气环流的独特性有关。 相似文献
7.
江汉平原6000年以来的古降水变化:江陵剖面沉积物粒度记录 总被引：6，自引：0，他引：6
通过对江陵剖面沉积物的高密度采样和粒度分析,重建了江汉平原江陵地区近6.0kaBP以来的古降水古气候变化序列：6.0～4.6kaBP为干旱阶段;4.6～2.5kaBP为湿润时期,该时期可以进一步划分为前、后两个阶段：前期阶段4.60～3.44kaBP降水波动频繁,其中4.60～4.27、4.16～3.95、3.80～3.68kaBP为湿润时期,而4.27～4.16、3.95～3.80、3.68～3.44kaBP为干旱时期;后期3.44～2.50kaBP为稳定的湿润阶段,湖沼泥炭发育,其中3.1～2.87kaBP为干旱阶段;2.50kaBP以来,由湖沼堆积转化为洪水漫滩堆积,气候变干或冷干。江陵地区6kaBP以来的古降水古气候变化与国内相邻区域及国外的研究资料一致。 相似文献
8.
用水热平衡模型估算青海湖古水文要素及水量平衡 总被引：7，自引：0，他引：7
根据水热平衡原理，推导了内陆湖泊水位高低（或面积大小）与流域降水及蒸发之间的定量关系，设计了青海湖古水量平衡计算模型。用现在的湖区气象要素及水量收支对模型进行了检验，然后将此模型用于估算全新世稳定暖湿期（7200－6000aB．P．）的青海湖古水文要素及水量平衡。结果显示，在全新世稳定暖湿期，青海湖流域的降水、蒸发及径流比现代高约32％，13％和67％。反映出该地区因气温高、降水增加造成的季风加强使得该地区的水量收支与现代相比有较大的不同。本方法用古湖水位来定量恢复古水文、气候参数，为此可以从古湖泊中提取古气候信息。 相似文献
9.
巴里坤湖泊沉积地层较好地记录了北疆东部地区全新世以来的气候变化。通过对沉积物粒度组分及碳酸盐含量的测量分析，结合测年结果，得出北疆东部地区全新世以来气候环境变化大致经历了5个阶段：（1）8700cal．aBP以前，为全新世早期，环境变干；（2）8700～8200cal．aBP，为一过渡期，湖泊面积扩大；（3）8200～7700cal．aBP，气候以变湿为主要特点，波动较大；（4）7700～2400cal．aBP，气候较为湿润，期间存在一次明显的突发强干旱事件；（5）2400cal．aBP以来，气候转干，剖面顶部指标指示环境恶化。区域气候变化以干湿为主要特点，5500～6000cal．aBP期间的突发气候事件在大区域上与其他记录对应较好。 相似文献
10.
62kaBP以来湖光岩玛珥湖沉积物有机碳同位素记录及古气候环境意义 总被引：18，自引：1，他引：18
湖光岩玛珥湖HUG-B孔岩心记录了62kaBP以来的古气候、古环境变化信息。全岩有机碳同位素组成(δ^13CTOC)分析表明，62kaBP以来δ^3CTOC值变化比较明显，其变化范围为-28．5‰～-15．5％0。结合孢粉和有机地球化学指标进行综合分析，湖光岩玛珥湖δ^13CTOC变化曲线可划分为6个演化阶段：62～58和48～40．5kaBP两个时段的δ^13CTOC值偏负，沉积物中有机质主要来源于热带-亚热带地区的陆生C13森林植被，反映了温暖潮湿的气候环境；58～48和40．5～17．2kaBP期间δ^13CTOC值明显偏正，沉积物中有机质主要源自C4草本植物，反映了湖光岩地区有效降水量减少、干旱程度增加导致湖光岩玛珥湖湖面下降，大量C4草本植物生长在暴露的湖滨岸；17．2～4kaBP时段内δ^13CTOC值尽管存在更加频繁的波动，但总体呈现逐渐偏负的趋势，反映了暖湿和冷干气候多次交替但总体上逐渐变暖、变湿的气候环境；4kaBP以来δ^13CTOC值存在逐渐偏正的趋势，虽然不排除人类活动的影响，但很可能反映了干旱程度的再次增加。综合分析表明，有效降水量(降水量-蒸发量)是控制湖光岩玛珥湖地区C3／C4植物相对生物量变化的主导因素。湖光岩玛珥湖有机碳同位素的研究结果支持区域气候环境而不是大气CO2浓度变化是末期冰期以来热带低纬度地区C3／C4植被相对生物量变化的主要原因。 相似文献
11.
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
12.
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
13.
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
14.
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
15.
16.
《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
17.
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
18.
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
19.
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
20.
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