High precision glacial–interglacial benthic foraminiferal Sr/Ca records from the eastern equatorial Atlantic Ocean and Caribbean Sea     

Chuan-Chou Shen  David W. Hastings  Typhoon Lee  Chin-Hsin Chiu  Meng-Yang Lee  Kuo-Yen Wei  R. Lawrence Edwards 《Earth and Planetary Science Letters》2001,190(3-4):197-209

Glacial–interglacial variation in the marine Sr/Ca ratio has important implications for coral Sr thermometry [J.W. Beck et al., Science 257 (1992) 644–647]. A possible variation of 1–3% was proposed based on ocean models [H.M. Stoll and D.P. Schrag, Geochim. Cosmochim. Acta 62 (1998) 1107–1118]. Subsequently, studies have used fossil foraminifera to test this prediction [P.A. Martin et al., Geochem. Geophys. Geosyst. 1 (1999); H.M. Stoll et al., Geochim. Cosmochim. Acta 63 (1999) 3535–3547; H. Elderfield et al., Geochem. Geophys. Geosyst. 1 (2000)]. But whether some component of foraminiferal Sr/Ca variation can be uniquely ascribed to seawater Sr variation is still not clear. To address this question, we developed cleaning and analysis techniques and measured Sr/Ca ratios on individual shells of the modern benthic foraminifer Cibicidoides wuellerstorfi. We showed that different size shells have different Sr/Ca ratios; however, samples with shell sizes of 355–500 μm appear to have normally distributed Sr/Ca ratios (1σ=1.8%). For multi-shell measurements (with estimated errors of 0.12–0.39%), the ratio varied by as much as 7.2±0.5% during the last glaciation for two Caribbean records at the same site and by 3.7±0.5% over the past 40,000 yr for one record from the Sierra Leone Rise in the eastern equatorial Atlantic. The two Caribbean records are very similar indicating that the behavior of shell Sr uptake was identical locally and that the shell Sr/Ca ratio faithfully reflects the local environment. The Atlantic record differs from the Caribbean records by as much as several percent. Thus, the foraminiferal Sr/Ca changes cannot be solely due to changes in seawater Sr/Ca unless the glacial deep ocean had spatial variation in Sr/Ca well in excess of the modern ocean. Certain similarities between the three records do exist. Notably, the rate of change of Sr/Ca is similar between 9 and 0 ka (−0.25%/kyr) and between 25 and 16 ka (+0.16%/kyr). This suggests that during these intervals, benthic foraminiferal Sr/Ca was affected by similar large-scale variables. One of these variables may be the average marine Sr/Ca ratio; however, comparison with model predictions [H.M. Stoll and D.P. Schrag, Geochim. Cosmochim. Acta 62 (1998) 1107–1118] suggests other factors must also be considered. The discrepancies between the two sites may be related to the different water mass histories for the Caribbean and eastern Atlantic. Our results suggest that variation of the seawater Sr budget only partially contributed to C. wuellerstorfi Sr/Ca records, while other significant factors still need to be quantified. At present we cannot confidently determine past seawater Sr/Ca variation from our foraminiferal records.  相似文献   

Structure refinement of astrophyllite   总被引：1，自引：0，他引：1  

马喆生  李国武  施倪承  周湖云  叶大年 《中国科学D辑(英文版)》2001,44(6):508-516

The crystal structure of astrophyllite K₂Na(Fe, Mn, Mg,□)₇[Ti₂(Si₄O₁₂)₂|O₃](OH, F)₄ has been refined. The dimensions of the triclinic unit cell are: a = 0.5359(2) nm,b = 1.1614(4) nm, c = 1.1861(4) nm, α= 113.16(2)°, β= 103.04(2)°,γ= 94.56(2)°,V = 0.6495(5) nm³, Z= 1, space group P1, R=0.057 for 5308 reflections |F_o|>3σ|F_o|. According to structural and compositional differences the monoclinic astrophyllite K₂NaNa(Fe, Mn)₄Mg₂Ti2[Si₄O₁₂]₂(OH)₄(OH, F)₂ and astrophyllite should be considered as two different mineral species. Astrophyllite, monoclinic astrophyllite, bafertisite and lamprophyllite contain heteropolyhedral sheets which topologically are related with Si, O sheets of mica where one or several SiO₄ tetrahedra are replaced by TiO _n polyhedra. Therefore this heterophyllotitanosilicate series represents a kind of functional substitution in inorganic crystals.  相似文献   

地下水流面三维实体模型制作系统（V1．00）     

于军 《江苏地质》2001,25(1):27-32

简要介绍了地下水流面在维实体模型制作系统－GWT3D（V1．00）的实体建模技术及光线跟踪原理，对其绘图所需数据文件结构进行了必要说明，同时阐述了GWT3D的功能与特色，并给出了该软件在这地区绘制地下水流场三维实体模型的一个实用实例。GWT3D是由VisualC 6.O开发的Win32应用程序，采用Outloow98流行的动画工具条风格，能利用通和地下水流模拟软件（如Modfolw等）所提供的网格剖分及水位数据，给制近似逼真的三维地下水流形态，具有动画显示功能和TIF、BMP、GIF3种图像文件存储格式，是一个专业性和实用性较强的计算机图像制作软件。  相似文献   

小兴安岭黑大公路沿线多年冻土分布及退化状态   总被引：3，自引：8，他引：3  

王彪  盛煜  刘建平 《冰川冻土》2001,23(3):302-306

黑大公路沿线多年土主要分布于黑河－北安段，属小兴安岭岛状多年冻土区，该区存在的多年冻土是晚全新世寒冷时期的产物，现处于欧亚多年冰土南界边缘，多年冻土发育在低洼、地表积水、塔头草生长茂密、草炭和泥炭发育的沼泽化湿地当中，沼泽湿地独特的热交换特性决定了其中发育的多年冻土处于退化的最晚阶段，冻土的退化在自然条件下可能依赖于由于至上的地下热流。多年冻土的地温剖面表现为零梯度曲且冰土温度接近于0℃，由此决定了多年冻土对人为活动干扰的敏感性。  相似文献   

浙江雷甸淡水无光珠中球文石的首次确认   总被引：1，自引：2，他引：1  

马红艳  戴塔根  袁奎荣  邓燕华 《矿物学报》2001,21(2):153-157

球文石（Vaterite)是CaCO3很不稳定的同质多象变体，在自然界里很少出现，通过光学显微镜在淡水无光珠中发现球文石尚属首次，本文研究了淡水无光珠内球文石的显微特征、X射线粉晶衍射特征及显微红外光谱特征，研究结果表明淡水无光珍珠内球文石粉晶衍射由强至弱五个强峰的d值为0.3266,0.2723,0.3553,0.1811,0.2057nm；其红外光谱特征波数为1489，1450,1420,1087,1050,876,830,762,743cm^-1。球文石的存在是影响淡水珍珠品质的主要内在因素之一。  相似文献   

有机酸对长石溶解度影响的热力学研究   总被引：16，自引：0，他引：16  

罗孝俊  杨卫东 《矿物学报》2001,21(2):183-188

为明确认识有机酸（草酸、醋酸）对长石溶解度及储层次生孔隙发育的影响，本文利用热力学方法，计算了不同温度、酸度下钾长石在含有醋酸根0.05mol/L、草酸0.0055mol/L的溶液中的溶解度及草酸和醋酸对溶液酸度的影响，计算的结果表明醒酸根与铝的络合作用只发生在偏酸性的溶液体系中，并且随温度升高要求酸度增加，实际的络合能力降低，醋酸根的络合作用对长石溶解度的增加作用极及有限，最高时不足一倍；但醋酸能有效地缓冲溶液酸度，从而提高长石溶解度。草酸根与铝的络合作用发生在弱碱性至酸性条件下，温度升高，络合能力增加，络合效应对长石溶解度，草酸根上铝的络合作用发生在弱碱性至酸性条件下，温度升高，络合能力增加，络合效应对长石溶出量的增加最多可达2个数量级以上，草酸的浓度太低无法通过缓冲溶液在较高的酸度下来促进长石的溶解，草酸和醒酸能否促进储层次生孔隙的发育取决于盆地流体的酸度及组成流体的缓冲体系。  相似文献   

新型环境矿物材料——堇青石质泡沫陶瓷的研制   总被引：5，自引：0，他引：5  

李金洪  鲁安怀  宋庭兵  黄英 《矿物学报》2001,21(3):481-484

以聚氨脂泡沫塑料为前驱体，高岭土、铝土矿和滑石为原料，经配方和工艺设计，制备了以堇青石为主晶相的泡沫陶瓷，制成品密度为0．310－0．447g/cm^3，气孔率为81．7％－87．6％，孔径为0．2－0．5mm,平均抗压强度为0．98MPa。探讨了烧成温度对材料气孔率、抗压强度和吸水率等性能的影响。  相似文献   

地下水氘过量参数的演化   总被引：18，自引：4，他引：18  

尹观  倪师军 《矿物岩石地球化学通报》2001,20(4):409-411

本文详细地介绍了提出水体氘过量参数 (d值 )的依据、源于大气降水的地下水氘过量参数 (d值 )的演化特点、影响因素、误差来源 ,并分析和讨论了应用中的一些问题。  相似文献   

地质异常理论在兰坪盆地演化中的应用     

廖崇高  刘登忠  杨武年  陈建平 《云南地质》2001,20(3):253-259

基于地质异常理论的分析，并结合兰坪盆地的地质、构造特点，充分发挥地壳升降系数法的定量化及其空间优势，对兰坪盆地地质、构造演化进行了形象、直观的表述，对进一步反演兰坪盆地独特构造格架形成的古应力场，具有十分重要的作用。  相似文献   

缅北中部脉金矿带控矿因素及成矿作用浅析     

何文举 《云南地质》2001,20(3):279-288

缅北中部，印缅岛弧及弧后盆地东侧、新生代造山带的前缘推覆构造带中，分布有许多脉金矿床及矿点，构成金矿带。矿带、矿田、矿床及矿体的形成、分布及其规模，受不同级别的近南北向逆冲断裂，及其间派生的北东向张性扩容断裂组成的剪切断裂带控制。可渗透的下麦尔组下部中一粗粒砂岩，起着很好的容矿作用。下麦尔组上部泥岩、细砂岩、粉砂岩和页岩互层单元，在携金热液的迁移、氧化硅的沉淀和矿质沉积定位等方面，可能起到圈闭作用。  相似文献