共查询到20条相似文献，搜索用时 46 毫秒
1.
云南鹤庆盆地的孢粉记录及1.0 Ma以来的构造抬升与气候变迁 总被引：6，自引：0，他引：6
依据鹤庆盆地168m钻孔孢娄资料，对该区1.0MaBP以来古植被演替的阶段性特征进行了研究，探讨了该区植被和气候对高原隆升不同阶段的响应特点。明显的气候转型发生在0.73和0.42-0.365MaBP。0.165MaBP前后，山体抬升引起的树线变化植被响应不甚明显，可以与山体上升到一定高度和垂直带谱的稳定形成有关，13.2kaBP时，构造的差异升降和气候变化导致湖盆被切穿。 相似文献
2.
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
3.
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
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.
本文根据厦门港湾12个柱样沉积物的抱粉分析结果，划分出三个饱粉带，探讨了其沉积环境与古气候演化史。Ⅲ榛属－藜科－水龙骨科带，以榛和草本为主，表明为稀树草原植被和温凉干燥气候，陆相沉积，形成于晚更新世晚期至早全新世；Ⅱ栎属、栲属、栗属一水龙骨科带，表明为繁盛的常绿阔叶林和茂密的灌木草本植被，气候最湿润暖热，为冰后期海面最高时期，海相沉积，形成于中全新世；I松属－禾本科－蕨属、水龙骨科带，由成类、草本和针叶树组成，表明主要为针叶树和栽培植被，气候转为暖干，现代沉积，即晚全新世。 相似文献
6.
东海陆缘地区晚第四纪沉积的孢粉及其古环境意义 总被引：10，自引：0，他引：10
张玉兰 《海洋地质与第四纪地质》2004,24(3):91-96
通过对东海陆缘地区东海1井、高桥G2孔、人民广场孔等晚第四纪地层的孢粉研究，划分出了6个孢粉组合带，并恢复了本地区植被演替、气候波动的6个阶段：第1阶段为稀疏的针叶、落叶阔叶混交林，反映气候冷干(晚更新世晚期)；第2阶段为针叶、阔叶混交林-草原，反映气候温凉略湿(前北方期)；第3阶段为舍常绿阔叶树的针叶、阔叶混交林，反映气候温和略干(北方期)；第4阶段为以栲属、青冈栎为主的常绿阔叶林，反映气候暖热潮湿(大西洋期)；第5阶段是以栎、松、蒿为主的针叶、阔叶混交林，反映气候温和略干(亚北方期)；第6阶段是以落叶栎类、常绿栎类、松为主的落叶阔叶、常绿阔叶、针叶混交林-草原，反映气候温暖湿润(亚大西洋期)。这种气候波动与世界性气候变化相一致，为本地区的地层年代划分和对比提供了可靠的证据，为晚第四纪古植被、古气候、古环境的重建提供了重要的孢粉学资料。 相似文献
7.
对东海北部陆缘地区NH 0504孔和东海Dh1井全新世地层的孢粉进行了研究,划分出5个孢粉组合带和2个亚带,恢复了该地区植被演替、气候波动和古环境演变的5个阶段,为该区的地层年代划分和对比提供了科学的证据,为全新世古植被、古气候和古环境的重建提供了重要的孢粉学资料。划分的5个阶段为:第1阶段为针阔叶混交林-草地,反映出当时的气候以温凉略湿为特征(前北方期);第2阶段为含常绿阔叶树的针阔叶混交林,反映出当时的气候以温和略干为特征(北方期);第3阶段为以常绿栎类和栲属等为主的常绿阔叶林,反映出当时气候以热暖潮湿为特征(大西洋期);第4阶段是以栎、松和禾本科为主的针阔叶混交林,反映出当时的气候以温暖略干为特征(亚北方期);第5阶段是以落叶栎类、常绿栎类、松为主的落叶阔叶、常绿阔叶、针叶混交林-草地,反映出当时的气候以温暖湿润为特征(亚大西洋期)。 相似文献
8.
长江三角洲前缘地区晚第四纪沉积的孢粉与环境研究 总被引：4，自引：0，他引：4
通过对长江三角洲前缘地区高桥G2孔、上海斜2孔等晚第四纪地层的孢粉研究,划分出了6个孢粉组合带,并结合临近钻孔的孢粉研究资料,恢复了本地区植被演替、气候波动的六个阶段:第一阶段为稀疏的针叶、落叶阔叶混交林,反映气候冷干(晚更新世晚期);第二阶段为针叶、阔叶混交林草地,反映气候温凉略湿(前北方期);第三阶段为含常绿阔叶树的针叶、阔叶混交林,反映气候温和略干(北方期);第四阶段以栲属、青冈栎为主的常绿阔叶林,反映气候暖热潮湿(大西洋期);第五阶段是以栎、松、蒿为主的针叶、阔叶混交林,反映气候温和略干(亚北方期);第六阶段是以落叶栎类、常绿栎类、松为主的落叶阔叶、常绿阔叶、针叶混交林草地.这六个阶段为本地区的地层年代划分和对比提供了可靠的证据,为晚第四纪古植被、古气候、古环境的重建提供了孢粉学资料. 相似文献
9.
对南海北部C4站柱状沉积剖面进行了高分辨率孢粉、藻类成分的分析和研究,同时测定了部分样品的AMS14C年代,划分了该站柱状沉积物地层时代,相应恢复了南海北部9 800 a B P以来植被、气候、环境的3个演替阶段.南海北部C4站从下至上可划分成3个孢粉组合带,依次为:1带(258～194 cm):以Pinus-Quercus(常绿)-Polypodiaceae-Pterdium-Pteris-Dicranopteris-Adiantum为主孢粉带;2带(194～94 cm):以Pinus-Quercus(常绿)-Pteridium-Polypodiaceae-Microlepia-Dicranopteris为主孢粉带;3带(94～4 cm):以Pinus-Pteridium-Polypodiaceae-Quercus(常绿)-Microlepia-Dicranopteris为主孢粉带.与3个孢粉带相对应的古植被阶段依次为:伴有针叶树的常绿阔叶、落叶阔叶混交林,热带半常绿季雨林,热带常绿阔叶、落叶阔叶混交林,与周边地区的植被演替相一致.由此可见,研究区经历了全新世早期气候转暖,中期气候炎热、干湿季明显、海平面上升以及晚期气候暖热、湿润3个古环境演变阶段. 相似文献
10.
对上海地区晚第四纪钻孔地层中的孢粉以及较高分辨率测年资料进行了分析.根据孢粉组合恢复了6个植被演替以及古气候期,和该区的海水进退吻合很好.研究发现,120～96 ka B.P.间处于里斯冰期末期,沉积物粗,孢粉稀少;96～84 kaB.P.间处于里斯一玉木问冰期,孢粉以落叶栎一松一枫香一常绿栎一栲为主,气候温暖略湿,海平面上升;84～64 kaB.P.间处于早玉木冰期,气候寒冷,孢粉稀少,海水退出本区;64～20]kaB.P.间处于玉木问冰期,孢粉组合以落叶栎-栗-麻栎-常绿栎-栲-蒿-水龙骨为主,常绿树种大量出现,气候温暖湿润,海平面回升,其中37～34 kaB.P.间气候稍微变凉;22～10 kaB.P.间为末次冰盛期,孢粉含量以及种类稀少,主要以针叶树种和耐干草本植物为主,反映气候冷凉干燥,海水全面退出本区;10 kaB.P.以来,气候开始转暖,尤其进入全新世大暖期后,孢粉以落叶栎-松-常绿栎-禾本科为主. 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.
15.
《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
16.
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
17.
18.
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
19.
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
20.
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