共查询到19条相似文献，搜索用时 296 毫秒
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中国西北地区第四纪盐湖沉积中钙质超微化石的发现及其古环境意义 总被引：4，自引：0，他引：4
报导了中国西北地区的甘肃、青海、新疆等地陆相第四纪盐湖沉积中发现的钙质超微化石,它们主要是：Ｇｅｐｈｙｒｏｃａｐｓａｏｃｅａｎｉｃａ,Ｃｏｃｏｌｉｔｈｕｓｐｅｌａｇｉｃｕｓ,Ｃａｌｃｉｄｉｓｃｕｓｌｅｐｔｏｐｏｒｕｓ,Ｃ．ｍａｃｉｎｔｙｒｅｉ,Ｒｅｔｉｃｕｌｏｆｅｎｅｓｔｒａｍｉｎｕｔｕｌａ等。上述钙质超微化石群具有以下特征：（１）化石丰度中等,属、种分异度低,化石保存差;（２）赋存化石的层位均为富含石膏盐层的微咸水咸水的沉积物,或为盐湖沉积;（３）产出化石地点远距该地质时期时的古海岸线。它们与古海域既无通道相连,亦非残留海。中国西北地区盐湖沉积中钙质超微化石的发现说明了中国东部地区第三纪沙河街组某些层位中的钙质超微化石不能作为“海相生物”的标志,否定了这些化石层位与“海侵”或“海泛”的关联。 相似文献
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生物壳化石地球化学的研究动态 总被引：2，自引：0，他引：2
生物壳化石地球化学是生物学和地球化学的边缘学科。五十年代以来,国内外学者先后应用生物壳化石微量元素、碳氧同位素组成,在研究古气候、古环境和进行年代对比等方面,开拓了一个新的学科领域。 一、科学依据 本文重点讨论陆相地层中,生物壳化石地球化学研究的科学依据和重要意义。 温度和降雨量是描述气候变化的主要参数。无论是哪种气候参数的改变,都可以使古湖盆中水体的酸碱度、盐度、水温、氧化—还原条件等发生改变,并且影响古生物组合面貌和沉积物特性。不同的古气候古环境 相似文献
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发现渤海湾中北部表层沉积硅藻21属37种,确定了Cyclotella striata/stylorum,Paralia sulcata和Coscinodiscusperforatus等9个优势种的地理分布;进而根据聚类分析,将研究区表层沉积硅藻划分为6个组合区。讨论了控制它们分布的环境因素,发现盐度与深度是重要控制因素,沉积物底质类型亦对硅藻的分布有一定的影响。 相似文献
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黄海晚更新世以来的硅藻组合及其沉积环境 总被引：3，自引：0，他引：3
黄海更新世晚期以来的硅藻化石,自下而上可划分为五个硅藻带。在Ⅰ带的上下层位,各含一个淡水藻类化石带,显示黄海在大理冰期时,由于气候变冷,海面下降,黄海陆架三次出露成陆。亚间冰期时,气候转暖,海面回升,复为海水淹没,海域中生长着Ⅰ带的各种海生硅藻。随着全新世气候转暖,沉积物中发现Ⅱ-Ⅴ带海生硅藻带,其中Ⅲ带硅藻外洋种比例较大,含亚热带暖海种多,表明此时水温较大,海域扩大,相当于大西洋期,其他各带与全新世各期相当。 相似文献
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废黄河南岸的青莲岗遗址是江淮东部重要的新石器遗址,了解其古环境背景变化对于认识该遗址的发展具有重要意义。通过对青莲岗遗址考古地层的AMS 14C年代、孢粉和硅藻的综合分析,探讨了海水对该遗址的影响及水环境的变化。研究结果表明,生土层堆积后期(5.9 cal.kaB.P.以前),孢粉中莎草科占绝对优势,伴生蒿和藜科,硅藻组合中半咸水属种为优势种,海水种破碎壳体较多,可能为水动力较强的滨海盐沼环境。新石器文化层堆积期(5.9~4.8 cal.ka B.P.),硅藻属种中半咸水种减少,淡水底栖附生种为主要优势种,海水种硅藻破碎壳体的个数快速下降,表明此时环境逐渐稳定,海水或半咸水的影响减弱,适宜新石器先民的生产和生活。孢粉中水生、湿生草本和大型禾本科花粉增加,表明浅水水域面积增大,稻作农业开始出现。历史和近代时期(4.8 cal.ka B.P.以来),大型禾本科花粉急剧降低,表明稻作活动基本不存在。此时,硅藻中海水种和海水种破碎壳体有所增加,表明受到海水一定程度的影响,水动力再次加强,可能与海水倒灌或古黄河的泛滥有关。 相似文献
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山东山旺中新世硅藻页岩中的遗迹化石 总被引：4，自引：0，他引：4
山东山旺中新世湖相沉积硅藻页岩下部，首次发现无脊椎动物潜穴遗迹化石。本文描述了这一新遗迹属及新遗迹种，定名为硅藻山旺迹讨论了遗迹动物的行为习性和沉积环境。该遗迹化石保存为全浮雕，为觅食迹。新遗迹特征为平直和销弯曲的管状潜穴。潜穴一般可不分枝或二分枝，二分枝时两侧枝近相互平行延伸，潜穴直径２－２．５ｍｍ，沿长度粗细变化不大，估计潜穴动物身体粗细与潜穴相适应，推测可能是由湖生的寡毛动物蠕虫类所形成。 相似文献
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内蒙古伊克昭盟地区盐湖生物地层与古气候研究 总被引：1，自引：0，他引：1
内蒙古伊克昭盟地区自全新世以来,湖沼发育,随气候的波动,大部分已演化成为盐湖。各类反映与气候有关的信息均保留在盐湖沉积物中。通过对其中具有代表性的4个盐湖5个钻孔剖面有关生物化石的鉴定与分析,发现介形类化石4个属种,硅藻39个属种和较多的植物种子、草茎及虫管化石。在含有抱粉层位的样品中分析出木本、草本及蕨类孢子等化石41个属种。通过对各钻孔剖面生物地层组合特征综合的分析表明,该区自全新世以来,其气候波动特点为暖湿→冷湿→温干→温凉湿润→凉干的气候波动格局。 相似文献
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In this study, we have investigated and clarified the processes occurring during the alteration of SON68 glass – the reference nuclear glass for the waste arising from reprocessing of spent fuel from light water reactors – at 50 °C in Callovo-Oxfordian clay groundwater in presence of magnetite. Magnetite is known to be one of the iron corrosion products expected to be present in the vicinity of glass in geological disposal conditions. The effects of the amount of magnetite relative to the glass surface and the transport of aqueous species during glass alteration were studied. A first series of experiments was focused on the effect of various magnetite amounts by mixing and altering glass and magnetite powders. In a second series of experiments, magnetite was separated from the glass by a diffusive barrier in order to slow down the transport of aqueous species. Glass alteration kinetics were analyzed and solids were characterized by a multiscale approach using Raman Spectroscopy, Scanning and Transmission Electron Microscopy, Energy-Dispersive X-ray and Scanning Transmission X-ray Microscopy coupled with Fe L2,3-edge and C K-edge NEXAFS.It appears that glass alteration increases with the amount of magnetite and that the transport of aqueous species is a key parameter. Several processes have been identified such as (i) the silica sorption on the magnetite surface, (ii) the precipitation of Fe-silicates in the vicinity of the glass (iii) the precipitation of SiO2 on the magnetite surface, (iv) the incorporation of Fe within the alteration layer. Process (iv) was not frequently observed, suggesting local variations in geochemical conditions. Moreover, this process is strongly influenced by the transport of aqueous species as indicated by the morphology and composition of the alteration layers. Indeed, when glass and magnetite are homogeneously mixed, the glass alteration layer consists of a gel enriched in Fe having the same Fe(II)/Fe(III) ratio as in magnetite. When both materials are separated by a diffusive barrier, the glass alteration layer consists of a porous gel (not enriched in iron) in presence of a mixture of Fe-silicates with Fe having the same valence as in magnetite, rare-earth precipitates and phyllosilicates. These results suggest that Fe incorporation within the alteration layer changes depending on the distance and the time required for dissolved Fe originating from the magnetite to reach the glass. 相似文献
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以合成雪硅钙石为晶种回收废水中的磷 总被引：2，自引：0，他引：2
以合成雪硅钙石为晶种,探索了用结晶法以磷酸钙形式回收废水中磷的适宜条件。结果表明,在实验水质条件下,模拟废水pH=8、n(Ca)/n(P)=2、晶种用量大于1.6g/L、振荡24h后溶液中残留磷可达到国家污水综合排放标准一级(0.5mg/L)以下;在优化条件下证实了合成雪硅钙石的供碱能力,循环利用18次,回收磷的效果仍然很好。运用XRD、FTIR、SEM和EDS等测试手段对在实验条件下重复使用18次的雪硅钙石进行了表征,证明回收的磷主要以结晶度不高的羟基磷灰石形态存在。 相似文献
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自然界中,菱锰矿氧化形成锰的氧化物矿物是非常普遍的现象,在菱锰矿被氧化分解发生物相转变的过程中,碳酸 盐溶解和锰的氧化往往同时发生,微生物可能起着催化作用。选取锰氧化模式菌株PseudomonasputidaMnB1和广西梧州菱 锰矿,通过菱锰矿在该细菌作用下发生转变的实验,利用场发射扫描电镜、扫描透射X射线显微成像等分析方法,研究了 矿石表面形貌变化以及锰元素在细胞上的分布特征。结果表明细菌显著促进的菱锰矿的溶解,在此基础上,进一步探讨了 细菌在菱锰矿氧化过程中的贡献,本实验结果丰富了次生锰矿床的微生物成因研究。 相似文献
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树皮煤的原子力显微镜研究 总被引：1，自引：0，他引：1
利用原子力显微镜观察了树皮煤中两种主要显微组分树皮体和镜质体表面纳米结构特征,揭示了镜质组镜质体大分子团具有网状结构的特征,而类脂组树皮体大分子团具有纤维状、颗粒状和网络状排列结构,随演化程度的提高,树皮体大分子团结构的演化依次表现为纤维状-→粒状-→不规则网状-→网状结构,镜质体则由结构松散的网状结构向高度定向排列的规则网状结构演化。利用AFM的横切面分析工具定量分析了显微组分表面的大分子结构排列,为显微组分分子结构演化和成烃机理研究提供了重要的科学依据。 相似文献
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Hemimorphite, Zn4Si2O7(OH)2·H2O, one of the most common minerals in non-sulfide Zn deposits, together with smithsonite and hydrozincite, is one of the most abundant minerals in the “calamine” deposits in SW Sardinia. In spite of their importance for the development of ore genesis models, the stability properties of hemimorphite are poorly known. This paper presents solubility experiments on two different types of hemimorphite: a “geological” hemimorphite from a supergene non-sulfide Zn deposit, of supposed abiotic origin, and a hemimorphite precipitated by bacterial activity. Both specimens were characterized, before and after the experiment, by Synchrotron Radiation X-ray powder diffraction, Scanning Electron Microscopy, and X-ray Absorption Spectroscopy. The calculated solubility product constants (logKs) are similar for both “geological” and biogenic hemimorphite (30.3 ± 0.4 and 30.5 ± 0.1, respectively). During the solubility experiment, biological hemimorphite undergoes an amorphous to crystalline phase transition, and the distinctive features (mineralized bacterial sheaths and organic filaments), that allowed us to demonstrate its biological origin, are no longer recognizable by Scanning Electron Microscopy.The results of this study may be useful for developing ore genesis models, including evolution in a supergene environment, and in general for performing geochemical speciation and equilibrium calculations. Moreover, our findings open the way for a new interpretation of hemimorphite-forming processes, and suggest the possibility that bacteria may have played a role in the formation of this mineral in ore deposits. 相似文献
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开展了湿干循环作用下压实黏土的开裂试验和微观结构特性研究,分析了湿干循环作用对黏土开裂和孔隙结构的影响,将压汞试验(MIP)和扫描电镜(SEM)的结果与宏观开裂进行比较。结果表明:湿干循环作用显著影响了压实黏土的开裂,用开裂因子表征黏土的开裂程度,开裂因子随含水率减小而增大并明显大于湿干循环作用前; 随湿干循环次数的增加,黏土孔隙的总体积、中间孔径、平均孔径、平均孔隙率和团粒内孔隙均在增加,而黏土的颗粒内孔隙、颗粒间孔隙和团粒间孔隙却在减小。湿干循环作用使黏土体从大团粒逐渐转化为小颗粒,并增大了土颗粒的凸凹性,分析SEM二值化图像得知土体孔隙率均在增加; 用压汞法和扫描电镜法分析和解释土体开裂是可行的,所得的微观孔隙特征与宏观开裂规律基本相符。 相似文献
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《Sedimentology》1967,8(1):81-86
Books review in this article:
Clays and Clay Minerals—Proceedings of the Fourteenth National Conference, Berkeley, California. S. W. B ailey (Editor).
Methods in Chemical and Mineralogical Microscopy . E. E. E l -H innawi
Primary Sedimentary Structures and their Hydrodynamic Interpretation . G. V. M iddleton (Editor). 相似文献
Clays and Clay Minerals—Proceedings of the Fourteenth National Conference, Berkeley, California. S. W. B ailey (Editor).
Methods in Chemical and Mineralogical Microscopy . E. E. E l -H innawi
Primary Sedimentary Structures and their Hydrodynamic Interpretation . G. V. M iddleton (Editor). 相似文献