Ice-core records of global climate and environment changes     

Robert J. Delmas 《Journal of Earth System Science》1998,107(4):307-319

Precipitation accumulating on the Greenland and Antarctic ice sheets records several key parameters (temperature, accumulation, composition of atmospheric gases and aerosols) of primary interest for documenting the past global environment over recent climatic cycles and the chemistry of the preindustrial atmosphere. Several deep ice cores from Antarctica and Greenland have been studied over the last fifteen years. In both hemispheres, temperature records (based on stable isotope measurements in water) show the succession of glacial and interglacial periods. However, detailed features of the climatic stages are not identical in Antarctica and in Greenland. A tight link between global climate and greenhouse gas concentrations was discovered, CO₂ and CH₄ concentrations being lower in glacial conditions by about 80 and 0.3 ppmv, respectively, with respect to their pre-industrial levels of 280 and 0.65 ppmv. Coldest stages are also characterized by higher sea-salt and crustal aerosol concentrations. In Greenland, contrary to Antarctica, ice-age ice is alkaline. Gas-derived aerosol (in particular, sulfate) concentrations are generally higher for glacial periods, but not similar in both the hemispheres. Marine and continental biomass-related species are significant in Antarctica and Greenland ice, respectively. Finally, the growing impact of anthropogenic activities on the atmospheric composition is well recorded in both polar regions for long-lived compounds (in particular greenhouse gases), but mostly in Greenland for short-lived pollutants.  相似文献   

四川石棉草科穹状岩浆核杂岩构造特征   总被引：1，自引：0，他引：1  

郭建强  喻安光 《矿物岩石》1998,18(4):90-97

位于扬子陆块西缘的石棉草科穹状变形变质体,据近年来的研究表明,该穹隆体经历了三次变形变质时期：早期为收缩滑脱变形的区域动力变质、中期热隆伸展动热变质和后期岩浆热接触变质。对主期变质划分出黑云母带、石榴石带、红柱石－十字石带和矽线石带,确定为低压相系,利用变质反应、矿物地质温压计及相关的同位素年龄资料,建立了草科穹状变形变质体演化的ｐ－Ｔ－ｔ－Ｄ轨迹。轨迹图呈顺时针形式,具碰撞造山带环境的特点,变形变质过程受变质体前缘西油房韧性剪切带逆冲－推覆作用和后缘碰撞晚期岩浆大规模上侵的双重制约,为深源岩浆热动力变质成因,属穹状岩浆核杂岩构造。  相似文献   

Formal subdivision of the Holocene Series/Epoch: a Discussion Paper by a Working Group of INTIMATE (Integration of ice‐core,marine and terrestrial records) and the Subcommission on Quaternary Stratigraphy (International Commission on Stratigraphy)     

M. J. C. Walker  M. Berkelhammer  S. Björck  L. C. Cwynar  D. A. Fisher  A. J. Long  J. J. Lowe  R. M. Newnham  S. O. Rasmussen  H. Weiss 《第四纪科学杂志》2012,27(7):649-659

This discussion paper, by a Working Group of INTIMATE (Integration of ice‐core, marine and terrestrial records) and the Subcommision on Quaternary Stratigraphy (SQS) of the International Commission on Stratigraphy (ICS), considers the prospects for a formal subdivision of the Holocene Series/Epoch. Although previous attempts to subdivide the Holocene have proved inconclusive, recent developments in Quaternary stratigraphy, notably the definition of the Pleistocene–Holocene boundary and the emergence of formal subdivisions of the Pleistocene Series/Epoch, mean that it may be timely to revisit this matter. The Quaternary literature reveals a widespread but variable informal usage of a tripartite division of the Holocene (‘early’, ‘middle’ or ‘mid’, and ‘late’), and we argue that this de facto subdivision should now be formalized to ensure consistency in stratigraphic terminology. We propose an Early–Middle Holocene Boundary at 8200 a BP and a Middle–Late Holocene Boundary at 4200 a BP, each of which is linked to a Global Stratotype Section and Point (GSSP). Should the proposal find a broad measure of support from the Quaternary community, a submission will be made to the International Union of Geological Sciences (IUGS), via the SQS and the ICS, for formal ratification of this subdivision of the Holocene Series/Epoch. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

On the nutations of a more realistic earth model   总被引：1，自引：0，他引：1  

V. Dehant 《Geophysical Journal International》1990,100(3):477-483

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深海原位取芯钻机作业机理分析及实验研究     

杨磊  丁忠军  李德威  李宝钢  杨雷  任玉刚  刘庆亮  刘敬喜 《海洋技术学报》2015,34(1):32-37

针对深海运载器海底岩芯原位取样作业需求,对基于水下运载器的深海原位取芯钻机在深海低温、高压、底层流速多变等特点条件下的作业机理及受力进行分析,并选取硬质合金钻头和PDC钻头进行了取芯钻头的轴向力、切向力和切削功率的数学力学对比计算,确定了单环四齿周向均布的金刚石复合片(PDC)钻头设计方案。在理论分析基础上,针对深海钴结壳设计了台架试验,开展钻进试验研究。通过理论计算和实验研究,探寻了一种基于深海运载器的钴结壳小型钻机设计方法,确定了钻机功率、转速、钻进正向压力和取芯率等基本参数选取范围,对开展海底岩芯原位取样作业具有重要的指导意义。  相似文献   

应用重力场模型GL1500E和LLR天平动参数估算月核大小及其组成     

钟振  张腾  段炼  李毅  朱化强 《武汉大学学报(信息科学版)》2021,(2)

针对月核大小及密度估计问题,利用高分辨率重力场模型GL1500E的二阶位系数和LLR(lunar laser ranging)天平动参数,考虑月核分层为外核和内核的情况,结合非线性粒子群优化算法,对月核大小和组成进行了估计。大批量的统计结果表明,大概率分布的外核半径rc1约为469 km,内核半径rc2约为303 km,外核密度ρc1约为4613 kg/m3,内核密度ρc2约为7004 kg/m3,月幔密度ρm约为3340 kg/m3。月幔密度非常接近地质研究结果3360 kg/m3,内外核半径与近期其他研究结果相近,估算的月核大小与密度组成具有一定的参考价值。若月核由纯铁和硫化亚铁组成,则研究表明,内核大部分由纯铁组成,外核大部分由硫化亚铁组成。  相似文献   

扬子克拉通西缘穹状变形变质体的类型与成因   总被引：4，自引：0，他引：4  

侯立玮 《四川地质学报》1996,(1)

扬子克拉通西缘呈分散状产出的一系列穹状变形交质体，按其结构特征与成因，可将其划分为变质核杂岩，岩浆核杂岩，片麻岩穹隆和构造穹隆四种类型。造山后期—期后，深部上隆，浅部伸展，局部岩浆活动和造山期深熔花岗岩底辟侵位所引起的地壳局部隆升与伸展，是形成该区变质核杂岩和岩浆核杂岩的主要原因；片麻岩穹隆和构造穹隆，则分别为双向挤压收缩体制下，局部熔融—重熔花岗岩同构造被动侵位，和单纯的构造变形与叠加变形形成。它们具不同的时、空分布和控矿特征，是扬子克拉通西缘造山过程中不同构造坏境，不同演化阶段和不同构造体制下的产物。  相似文献   

福建省兴化湾、九龙江河口和东山湾潮间带沉积物岩心碘研究     

纪丽红  刘广山  李超  陈志刚  黄奕普 《海洋学报》2013,35(5):177-183

用碱熔法处理样品,水沥取,用分光光度法测量了采集自福建省兴化湾、九龙江河口和东山湾3个海湾潮间带沉积物岩心的碘分布。兴化湾、九龙江河口和东山湾3岩心中的碘含量分别为2.5~43.7,17.3~39.6和11.3~29.1 mg/kg。3个沉积物岩心中的碘含量稍高于福建省的土壤的碘含量,与我国海域的沉积物碘含量在同一水平,但明显低于文献报道的开阔海域沉积物的碘含量。兴化湾和东山湾沉积物中的碘与有机碳含量有较好的相关性;在九龙江河口采集的岩心中的碘与有机物碳含量的相关性较差。推测海洋源的沉积物碘与有机碳含量相关性较好,而陆源沉积物的碘与有机碳含量相关性较差。  相似文献   

南海神狐海域水合物三相混合层测井评价方法研究     

谢莹峰  陆敬安  匡增桂  康冬菊  王通  蔡慧敏 《现代地质》2022,36(1):182-192

天然气水合物降压试采过程中,水合物、游离气和水的三相混合层中的游离气首先被采出,从而提高降压效率,促进水合物分解;因此利用岩心刻度测井的方法开展南海神狐海域水合物三相混合层测井评价方法研究,对水合物矿体储量计算以及产业化开采具有重要意义.三相混合层与水合物层相比,其密度和中子孔隙度值均减小,纵波速度明显下降;与气层相比...  相似文献   

钻探岩心高光谱数据管理与分析系统的构建     

黄艳菊  张杰林  王俊虎 《国外铀金地质》2010,(3):159-163

钻探岩心编录一直是地质勘探中至关重要的环节,高光谱探测技术的发展为岩心分析提供了一种新的编录技术。为了使获得的岩心资料能永久保存且便于使用和分析,笔者开发了钻探岩心高光谱数据管理与分析系统。通过该系统使用者能方便管理、查看钻探岩心数据,快速提取、分析岩心矿物的光谱特征,为后期矿物的识别奠定了基础。  相似文献