Changes in clay mineral content of tidal flat sediments resulting from dike construction along the Lower Saxony coast of the North Sea, Germany

The clay mineral content of the < 2 µm fraction in tidal flat sediments in the former Harle Bay on the Lower Saxony coast has changed considerably since the thirteenth century up to the present time. The proportion of smectite has decreased from 29 to 11 wt%, whereas the proportion of illite has increased by about 10 wt% and those of chlorite and kaolinite by about 3 wt% each. The chemical composition of the major clay mineral illite has also changed: Al₂O₃ has decreased by about 2 wt%, K₂O by about 1·5 wt% and SiO₂ by about 3 wt%. It can be concluded that the changes in the clay mineral content are mainly influenced by dike construction and sea level rise, modifying flow pattern, submarine morphology, sedimentation and tidal range. These processes cause smectite to settle less rapidly because of its small grain size and low density resulting from interlayer water, so that the sediment becomes impoverished in this mineral.     

Determination of Major/ Minor and Trace Elements in Seamount Phosphorite by XRF Spectrometry

In this paper, a method developed to determine the major, minor and trace elements, including carbon and the four halogens, in seamount phosphorite involving a modern XRF spectrometry technique is described. Ultra-fine (99% v/v < 40 μm) powder samples (4 g) were directly pressed into pellets (Φ= 30 mm). For elements having an analytical line lower in energy than the energy of Fe Kα line absorption edge, the inter-element absorption-enhancement effects were corrected using an influence coefficient method. For the other elements, the matrix effects were corrected using the ratio of element peak to Rh Kα Compton peak (for I, Rh K|3 Compton peak was used instead). The relative standard deviation was smaller than 1.0% for the major elements (except C, Na and Cl). The detection limit levels of C, F, Cl, Br and I were 30, 20, 0.8, 0.2 and 0.3 (μg g⁻¹ respectively for 100 s count time of background. The accuracy of this method was tested by evaluating determinations on three certified reference materials. The direct analysis of major and minor elements in geological materials by pressed pellet without any chemical procedures makes XRF spectrometry a particularly environment-friendly analytical technique.     

川西地区中三叠统雷口坡组岩相古地理

川西地区中三叠世雷口坡期位于威西蒸发海盆的西南部．盆地边缘及相邻地区主要发育潮坪相碳酸盐岩及少量的蒸发岩类，向盆地内部，除晚期部分地区发育碳酸盐岩外，硬石膏岩、石盐岩、杂卤石岩等蒸发岩类不断增多．区域上，岩相的垂向和平面相变明显。不同古地理位置的白天岩碳、氧同位素分析结果表明，盆地边缘的沉积作用和白云石化作用受到来自古陆方向的淡水影响。     

莫霍计划的回顾与展望

“莫霍计划”是20世纪50年代末提出来的堪与“登月计划”相媲美的最宏伟的科学计划之一。它开启了大洋钻探的新篇章，拉开了探索大洋岩石圈的序幕。历经半个多世纪的深海探索，研究学者逐渐揭开了洋壳结构的复杂性和多变性，其中代表下洋壳层3的辉长岩乃至地幔岩剥露的大洋核杂岩，为莫霍钻的实施提供了捷径和优选区。本文综述了“莫霍计划”以来在洋壳结构、洋壳增生机制和大洋核杂岩方面的研究进展，通过分析国际上莫霍计划的选址和策略，结合我国南海洋壳的特征，初步提出“南海莫霍计划”的两个站位及策略：① 南海残余洋中脊附近的U1431孔，该孔已钻到玄武岩层，可通过重复钻进钻穿莫霍面；② 南海东缘残余扩张脊的管事海山，可能有下洋壳辉长岩剥露，可在该区域采取多阶段钻探钻穿莫霍面。     

滇东黔西二叠纪含煤岩系潮坪沉积构造

作者论证古代潮坪沉积物的判据有:(l)扁平泥砾;(2)泥冲槽构造,(3)单、双粘土层;(4)潮汐周期层序(递变式和规律间隔层组式);(5)垂直剖面中的“二元”韵律,即高、低流态成对沉积物的相互交替。潮汐周期层序已在蛇曲状潮汐水道沉积物的垂直层序中被发现,并横向过渡为具有泥冲槽的潮坪沉积物,两者间为冲刷接触。     

滇西南古特提斯石炭纪海山碳酸盐台地的层序地层学研究

应用露头层序地层学原理和方法，首次对滇西古特提斯（昌宁－孟连带）中海山碳酸盐台地的石炭系进行了研究。识别出６个三级层序，其中早石炭世晚期１个、威宁期３个、鱼塘寨组３个，顶部一个归属二叠纪。三级层序和相应的海平面变化旋回可以和黔南对比，但副层序厚度较大（黔南副层序小于１０ｍ，鱼塘寨１０～５０ｍ），碳、氧同位素普遍偏轻以及存在麦粒蜓带厚度变薄事件，造成这种现象的主要原因是两者之间经历了同样的冰川型全球海平面变化，但具有不同的大地构造背景.     

长江河口崇明东滩周期性淹水区域水流的基本特征

潮间带周期性淹水区域水深、流速的变化过程是潮滩水动力过程的基本组成部分,也是潮流与泥沙相互作用的基础。通过2002年4月至2003年1月4个季节的野外实测,获得了平静天气条件下,崇明东滩滩面潮流水深、流速与流向的变化过程数据。结果表明,崇明东滩盐沼和邻近光滩处涨潮历时均小于落潮历时,水深过程变化呈现出“陡涨缓落”的特点。光滩与盐沼交界处光滩一侧流速过程呈“双峰型”特征,涨落潮均出现流速峰值;盐沼（植物生长期）流速过程具有“单峰型”特点,仅在涨潮初出现峰值。研究区潮流不对称性明显,主要表现为涨潮优势,且由光滩向盐沼上部不断增强,潮沼植物和地形变化是加强盐沼区涨潮优势的主要原因。流速变化过程的差异和潮流不对称性使盐沼区域发生稳定的泥沙淤积,盐沼前缘光滩则会出现较频繁的冲淤变化,平静天气条件下,它们是控制崇明东滩泥沙输移和潮滩动力地貌过程的动力基础。     

数字高程模型预处理方法的研究进展

数字高程模型(Digital Elevation Model,简称DEM)是地形表面形态属性的数字化表达,被广泛应用于流域水文模拟中河网水系的提取.从DEM直接提取的河网水系及相关的流域地理空间信息,是分布式水文模拟的地理信息平台.由于DEM中洼地和平坦区的存在会影响水流方向的确定和数字河网的正确提取.因此在河网自动提取过程中必须首先对DEM数据进行预处理.本文对国内外各种DEM预处理方法进行了归纳总结.将DEM数据预处理方法分为两大类:分步处理法,以及一体化处理法.分步处理法按处理对象又可分为洼地处理方法和平坦区处理方法两部分;而一体化处理法则采用迭代算法同时对洼地和平地进行处理.     

广西晚二叠世成煤模式探讨

广西晚二叠世成煤模式划分为“两类三型”,即泥炭沼泽成煤模式和泥炭坪成煤模式两类,沼泽型、潮坪型和泥炭坪型等三型。文章阐述了这些成煤模式在吴家坪期和长兴期形成的特征,分布状况,以及代表煤层,指出潮坪型是广西晚二叠世时期最主要的成煤模式。