Biostratigraphic and aminostratigraphic constraints on the age of the Middle Pleistocene glacial succession in north Norfolk,UK

Considerable debate surrounds the age of the Middle Pleistocene glacial succession in East Anglia following some recent stratigraphical reinterpretations. Resolution of the stratigraphy here is important since it not only concerns the glacial history of the region but also has a bearing on our understanding of the earliest human occupation of north‐western Europe. The orthodox consensus that all the tills were emplaced during the Anglian (Marine Isotope Stage (MIS) 12) has recently been challenged by a view assigning each major till to a different glacial stage, before, during and after MIS 12. Between Trimingham and Sidestrand on the north Norfolk coast, datable organic sediments occur immediately below and above the glacial succession. The oldest glacial deposit (Happisburgh Till) directly overlies the ‘Sidestrand Unio‐bed’, here defined as the Sidestrand Hall Member of the Cromer Forest‐bed Formation. Dating of these sediments therefore has a bearing on the maximum age of the glacial sequence. This paper reviews the palaeobotany and describes the faunal assemblages recovered from the Sidestrand Unio‐bed, which accumulated in a fluvial environment in a fully temperate climate with regional deciduous woodland. There are indications from the ostracods for weakly brackish conditions. Significant differences are apparent between the Sidestrand assemblages and those from West Runton, the type site of the Cromerian Stage. These differences do not result from contrasting facies or taphonomy but reflect warmer palaeotemperatures at Sidestrand and a much younger age. This conclusion is suggested by the higher proportion of thermophiles at Sidestrand and the occurrence of a water vole with unrooted molars (Arvicola) rather than its ancestor Mimomys savini with rooted molars. Amino acid racemisation data also indicate that Sidestrand is significantly younger than West Runton. These data further highlight the stratigraphical complexity of the ‘Cromerian Complex’ and support the conventional view that the Happisburgh Till was emplaced during the Anglian rather than the recently advanced view that it dates from MIS 16. Moreover, new evidence from the Trimingham lake bed (Sidestrand Cliff Formation) above the youngest glacial outwash sediments (Briton's Lane Formation) indicates that they also accumulated during a Middle Pleistocene interglacial – probably MIS 11. All of this evidence is consistent with a short chronology placing the glacial deposits within MIS 12, rather than invoking multiple episodes of glaciation envisaged in the ‘new glacial stratigraphy’ during MIS 16, 12, 10 and 6. Copyright © 2009 John Wiley & Sons, Ltd.     

Statistical analysis of sand grain/bed collision process recorded by high-speed digital camera

A high‐speed digital camera was employed to record the sand grain/bed collision process. With image processing and a statistical method, a series of parameters of the collision process were obtained. The results show that the collision process of a grain with rebounding can be represented by two parameters: the kinetic energy restitution coefficient and the collision angle. Both parameters satisfy a normal distribution, and they are dependent on one another. With an increase of the collision angle, the distribution of the kinetic energy restitution gradually reduces from a broad to a narrow range with low values. The percentage of vertical velocity restitution coefficients greater than 1 can reach 70% or more, which ensures that the settling time of the sand grains in the air increases and that they receive more energy from the air to progress the saltation movement.     

扬子及周缘地区上奥陶统-下志留统烃源岩发育环境及其控制因素

扬子地区下古生界发育了上奥陶统五峰组和下志留统龙马溪组两套有效烃源岩,查清其发育环境及其控制因素具有重要的科学理论和油气勘探意义.晚奥陶世开始,扬子地区进入碎屑岩陆棚演化阶段;五峰期-龙马溪期,扬子地区主体为局限的深水陆棚环境,总体呈现出浅水陆棚、深水陆棚、次深海共存的古地理格局.沉积体系展布和沉积演化主要受扬子陆块与华夏陆块的汇聚作用控制.扬子地区上奥陶统-下志留统烃源岩的形成与生烃母质生物的高生产力和高埋藏率、冰期-冰后期之交的气温快速转暖、海平面快速上升以及粘土矿物在有机质富集保存过程中的赋存驻留作用等密切相关.     

煤岩对压裂裂缝长期导流能力影响的实验研究

煤层中一般都伴有煤层气,通过压裂可以将煤层气释放出来,一方面能够获得清洁能源,另一方面可以提高煤田的安全开采。煤岩层自身特点决定了其在压裂中应用的实验评价方法及结论应具有特殊性,本文主要针对煤层气井的煤岩层压裂裂缝长期导流能力进行实验评价研究。实验表明,与砂岩地层不同,煤岩的硬度较小,压裂中支撑剂嵌入情况较严重;煤岩易破碎,碎屑颗粒充填到支撑剂中;同时支撑剂存在破碎及吸附伤害等,多种作用导致支撑裂缝的导流能力降低。实验中,以煤岩层闭合压力为一个重要的参数,实验对比分析了在不同闭合压力下,铺砂浓度、支撑剂粒径、支撑剂种类及组合的选择、支撑剂颗粒的破碎与嵌入、压裂液残渣等因素对煤岩层导流能力的影响。本文的实验结论为,嵌入对煤岩层支撑裂缝的导流能力伤害很大,加大铺砂浓度、采用低破碎率支撑剂、降低压裂液伤害能在一定程度上提高煤层裂缝的导流能力,但影响程度随闭合压力的增加而逐渐降低。本文所得出的结论对今后煤层气的开发及设计施工具有一定的指导意义。     

Interference of Multiple Strip Footings on Sand Using Small Scale Model Tests

By using small scale model tests, the interference effect on the vertical load-deformation behavior of a number of equally spaced strip footings, placed on the surface of dry sand, was investigated. At any stage, all the footings were assumed to (i) carry exactly equal magnitude of load, and (ii) settle to the same extent. No tilt of the footing was permitted. The effect of clear spacing (s) among footings on the results was explored. A new experimental setup was proposed in which only one footing needs to be employed rather than a number of footings. The bearing capacity increases continuously with decrease in spacing among the footings. The interference effect becomes further prominent with increase in soil friction angle. In contrast to an increase in the bearing capacity, with decrease in spacing of footings, an increase in the footing settlement associated with the ultimate state of shear failure was observed. The present experimental observations were similar to those predicted by the available theory, based on the method of characteristics. As compared to the theory, the present experimental data, however, indicates much greater effect of interference especially for larger spacing among footings.     

河口区治江围涂对杭州湾水动力及海床影响分析

自二十世纪六十年代起，钱塘江河口进行了大规模治江围涂，人类活动对杭州湾水域的影响越来越为人们关注。基于实测资料的分析和潮汐水流数学模型计算，探讨了钱塘江河口区围涂对杭州湾水域潮汐水流和海床的影响。研究成果可为钱塘江河口和杭州湾的进一步开发治理和环境保护提供科学依据。     

纳米碳酸钙材料的工业合成与应用

该文对目前工业上生产纳米碳酸钙的方法作了较为详细的综述。对一步碳化法、两步碳化法、多段喷雾碳化法、旋转填充床碳化反应器碳化技术制备链形、纺锤形、球形、立方形等不同形状的纳米碳酸钙材料的方法进行了比较和总结     

Burial and scour around short cylinder under progressive shoaling waves

The results of a laboratory experimental program aimed at better understanding the scour around and burial of heavy cylindrical objects under oscillating flow on a sandy bed are described. This study was motivated by its application to the dynamics of isolated cobbles/mines on a sandy floor under nonlinear progressive waves, such as that occur in shallow coastal waters beyond the wave-breaking region. In the experiments, nonlinear progressive waves were generated in a long wave tank of rectangular cross-section with a bottom slope. Model mines (short cylinders) were placed on the sandy bottom and the temporal evolution of the bed profile and the velocity field in the near field of the object were observed. Experiments were conducted at relatively high Reynolds numbers for a range of flow conditions, which can be characterized by the Keulegan–Carpenter number and Shields parameter. Depending on the values of these parameters, four different scour regimes around the cylinder including periodical burial of cylinder under migrating sand ripples were observed; they were classified as: (i) no scour/burial, (ii) initial scour, (iii) expanded scour, and (iv) periodic burial cases. A scour regime diagram was developed and the demarcation criteria between different regimes were deduced. Semi-empirical formulae that permit estimation of the scour depth with time, the equilibrium maximum scour depth and length, and conditions necessary for the burial of the cylinder as a function of main external parameters are also proposed.     

黄河三角洲河道沉积规律研究Ⅱ. 建林边滩沉积作用机理

通过对建林边滩沉积物粒度分布、粒度参数及水体流变性质的分析，阐述了黄河三角洲上河道水流属于牵引流范畴，与低含沙水流无本质上的差别，并探讨沉积物搬运和沉积的基本特征。     

底部浮泥表层推移速度分布的ADCP—GPS估测方法

ADCP对底跟踪走航观测的流速数据中包含水体底部浮泥、底沙运动信息,对比GPS定位方法算出的水体流速数据可以分离出浮泥相对于GPS定位的运动信号,从而达到对底质推移观测的目的。