南海北部全新世早期低钙事件及其古气候解释   总被引：5，自引：3，他引：5       下载免费PDF全文

李学杰  江茂生 《古地理学报》2003,5(3):355-364

碳酸盐旋回是南海晚更新世以来的最重要沉积特征之一，它受控于表层海水生产率、陆源物质的稀释作用以及深水对碳酸盐的溶解作用。南海北部碳酸钙百分含量主要受控于陆源物质对碳酸盐的稀释作用，即海平面低位时陆源碎屑经过陆架进入较深海域增多，也称稀释旋回。对西沙海槽北侧陆坡柱状样高分辨率研究后发现，在冰消期，低海平面时期存在高碳酸钙，而在冰后期的早中期，6～8ka B．P．的高海平面时期，却存在短暂的碳酸盐含量急剧下降的过程，即低钙事件，产生这种短暂的碳酸钙与其旋回性不吻合的现象应该是降雨量变化造成。在冰消期，出现干旱，陆源物质减少，而早中全新世的雨量，尤其是具较强冲刷能力的大雨量急剧增加。造成北部海南岛和华南陆地的冲刷增强，陆源物质供给增加，从而出现低钙事件。  相似文献   

The Baltic Sea Experiment BALTEX: A brief overview and some selected results of the authors     

Ehrhard Raschke  Ute Karstens  Ralph Nolte-Holube  Rüdiger Brandt  Hans-Jörg Isemer  Dag Lohmann  Manfred Lobmeyr  Burkhardt Rockel  Rolf Stuhlmann 《Surveys in Geophysics》1998,19(1):1-22

The mechanisms responsible for the transfer of energy and water within the climate system are under worldwide investigation within the framework of the Global Energy and Water Cycle Experiment (GEWEX) to improve the predictability of natural and man-made climate changes at short and long ranges and their impact on water resources. Five continental-scale experiments have been established within GEWEX to enable a more complete coupling between atmospheric and hydrological models. One of them is the Baltic Sea Experiment (BALTEX).In this paper, the goals and structure of BALTEX are outlined. A short overview of measuring and modelling strategies is given. Atmospheric and hydrological model results of the authors only are presented. These include also the validation of precipitation using station measurements as well as validation of modelled cloud cover with cloud estimates from satellite data. Furthermore, results of a large-scale grid based hydrological model to be coupled to atmospheric models are presented.This research has never been possible without the contribution of research groups and operational institutions from all 10 member countries. We concentrate here on results obtained at the GKSS research center.  相似文献   

塔里木盆地北部显生宙基准面升降运动规律与沉积演化   总被引：1，自引：0，他引：1       下载免费PDF全文

樊太亮  徐怀大  刘金辉 《地球科学》1998,23(6)

沉积基准面升降变化及其规律是各种地质因素综合作用的结果,又是控制地层发育和沉积作用的主导因素．地震剖面中上超点的迁移变化规律和测井资料中Ｍｉｌａｎｋｏｖｉｔｃｈ旋回分析是研究沉积基准面变化的有效方法．塔里木盆地北部显生宙沉积基准面变化曲线由１３个长周期构成,并可组合为６个一级周期．基准面变化在三叠纪以前与全球海平面变化有着良好的一致性,三叠纪及其以后可比性较差．与控制沉积作用的基准面变化周期相对应,塔里木盆地沉积地层分为６个一级巨层序,不同的巨层序有着不同的沉积充填演化特征  相似文献   

The South China Sea warm-core ring 94S and its influence on the distribution of chemical tracers   总被引：5，自引：1，他引：5  

Li Li  Thomas Pohlmann 《Ocean Dynamics》2002,52(3):116-122

 In this paper, the distributions of currents and chemical tracers were studied along two hydrographic sections across ring 94S, a warm-core ring found in the South China Sea. Results suggest that while currents on its offshore side maintained quasigeostrophic balance, such a balance was not reached on its onshore side. Therefore, it is suggested that interactions of ring 94S with the slope may play an important role: it may break down the quasigeostrophic balance and cause a deformation of the current field. The observed distribution of δ¹⁸O supports the hypothesis that water masses inside the ring originate from the Kuroshio. Distributions of chemical tracers reveal a strong vertical disturbance of the isolines at the edge of ring 94S, where it approaches the shelf. This phenomenon may play an important role in the vertical exchange of biochemical elements across the thermocline. Possible reasons, i.e., enhanced vertical mixing and upwelling, are discussed. Received: 16 May 2001 / Accepted: 5 November 2001  相似文献   

Earth nutation influence on system dynamics of Northeast Arctic cod   总被引：2，自引：1，他引：1  

Yndestad  H. 《ICES Journal of Marine Science》1999,56(5):652-657

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Tectonic feedback and the earthquake cycle     

Cinna Lomnitz 《Pure and Applied Geophysics》1985,123(5):667-682

The occurrence of cyclical instabilities along plate boundaries at regular intervals suggests that the process of earthquake causation differs in some respects from the model of elastic rebound in its simplest forms. The model of tectonic feedback modifies the concept of this original model in that it provides a physical interaction between the loading rate and the state of strain on the fault. Two examples are developed: (a) Central Chile, and (b) Mexico. The predictions of earthquake hazards for both types of models are compared.  相似文献   

黔南地区早、中泥盆世沉积演化的动力机制   总被引：3，自引：0，他引：3  

陈代钊  陈其英 《沉积学报》1995,13(3):54-65

泥盆纪时，黔南地区为一相对稳定的台地，早泥盆世晚期，海水开始漫漫其上.初始发育陆源碎屑沉积体系，中泥盆世发育陆源碎屑～碳酸盐混合体系.空间配置有下列几种类型:滨岸障壁～泻湖～河流体系，碳酸盐缓坡～滨岸障壁～泻湖体系，镶边型碳酸盐台地～泻湖三角洲（潮坪）体系，碳酸盐缓坡～三角洲体系。基底断裂限定了台地和台间沟的延限范围和演化进程，这两种不同沉积背景的沉积演化旋回可能主要受海平面变化控制。  相似文献   

The genesis of Lofer cycles of the Dachstein Limestone,Northern Calcareous Alps,Austria     

A. K. Satterley  R. Brandner 《International Journal of Earth Sciences》1995,84(2):287-292

Peritidal carbonate platform Lofer cycles have been regarded as a record of sea-level oscillations driven by variations in the earth's orbit. Fresh analysis of a newly measured 700 m thick section from the Steinernes Meer is presented here. Estimation of stratigraphic completeness indicates that this sequence is only 0.75–9.5% complete, strongly suggesting that Milankovitch patterns are not preserved. Analysis of cycle thickness-frequency distributions reveals an exponential pattern, strongly suggestive of aperiodic, random deposition rather than periodic deposition in response to orbital forcing. Evidence for the importance of autocyclic processes (e.g. lateral migration of inter- to supratidal mudbanks and subtidal areas) and syn-sedimentary tectonic downfaulting events within this already active Late Triassic extensional zone is presented.  相似文献   

Water quality impacts from on-site waste disposal systems to coastal areas through groundwater discharge     

P. J. Harris 《Environmental Geology》1995,26(4):262-268

This report summarizes research studies linking on-site waste disposal systems (OSDS) to pathogen and nutrient concentrations in groundwater with the potential to impact coastal embayments. Few studies connect OSDS to coastal water quality. Most studies examined pathogen and nutrient impacts to groundwater and omitted estimations of contaminants discharged to surface water. The majority of studies focused on nitrogen, with little information on pathogens and even less on phosphorus. Nitrogen discharged from OSDS poses the greatest threat to water quality. Vertical distance of septic tank infiltration system from the water table, septic system design, and siting remain the key components in minimizing potential impacts from OSDS for control of both pathogens and nutrients. The most comprehensive information connecting nutrient contributions from OSDS to surface water quality was the study conducted on Buttermilk Bay in Massachusetts where 74% of nitrogen to the bay was attributed to onsite disposal systems. In conclusion, further studies on the viability and transport of pathogens and nutrients through the groundwater aquifer and across the groundwater/surface-water interface are needed. Additional research on the importance of septic system design on the availability of contaminants to groundwater as well as the minimum distance between the septic system and water table necessary to protect groundwater are also indicated.  相似文献   

东太平洋锰结核中叠层石纹层周期信号的谱分析及其意义   总被引：4，自引：3，他引：4  

韩喜球  王惠群等 《地质学报》2001,75(4):548-553

利用光学显微镜对一取自东太平洋的光滑型锰结核中的叠层石纹层进行分级统计，得到纹层带、纹层组和纹层对的韵律周期分别约为500μm、50－42．8μm和11－9．0μm。利用电子探针线扫描分析获取了锰结核磨光面上一生长剖面（长0．7mm)的Si、Al、Fe、Mn元素的含量变化序列，运用功率谱分析方法识别出上述4种元素序列具有111．3μm、46．5－40．6μm、24．9－28．1μm、23．1－23．9μm和11．7－13．4μm的显著振荡周期。除了纹层带周期由于受剖面长度限制没有出现外，显微镜下统计得到的叠层石的纹层组和纹层对周期在元素序列的功率谱分析结果上均得到了反映。通过对锰结核生长速率的讨论，认为锰结核的纹层韵律很可能与地球轨道参数的周期性变化有关，纹层组周期可能对应地球轨道的黄赤交角变化周期，纹层对周期可能对应地球轨道的半岁差周期，所研究剖面叠层石的生长速率约为1．134mm/Ma。  相似文献