南海西部表层沉积物钙质浮游生物分布与碳酸盐溶解

对南海西部300多个表层沉积样品中的浮游有孔虫和钙质超微化石定量分析表明，几乎所有样品均含浮游有孔虫、钙质超微化石，但丰度相差十分悬殊，浮游有孔虫丰度介于0．5～36673个／g之间，钙质超微化石丰度为0～1725个／10个视域，两者的分布规律相似。在陆坡区钙质浮游生物最富集，尤其在西沙群岛西南、南沙西部礁滩附近海区丰度最高；向深海盆区和陆架浅水区，钙质浮游生物丰度均下降。但从两者的丰度分布来看，其溶解程度不同，浮游有孔虫更容易溶解，在200～2000m水深区，丰度最高，2000m以下丰度锐减；而钙质超微化石的最富集区在500～3000m，且3000m以下仍较丰富。从碳酸盐的分布来看，本区碳酸盐的临界补偿深度(CCrD)为3500m，而CCD大于4300m，碳酸盐的溶解主要由有孔虫和钙质超微化石构成。     

Characteristics of particle size for creeping and saltating sand grains in aeolian transport

Creep and saltation are the primary modes of surface transport involved in the fluid‐like movement of aeolian sands. Although numerous studies have focused on saltation, few studies have focused on creep, primarily because of the experimental difficulty and the limited amount of theoretical information available on this process. Grain size and its distribution characteristics are key controls on the modes of sand movement and their transport masses. Based on a series of wind tunnel experiments, this paper presents new data regarding the saltation flux, obtained using a flat sampler, and on the creeping mass, obtained using a specifically designed bed trap, associated with four friction velocities (0·41, 0·47, 0·55 and 0·61 m sec^?1). These data yielded information regarding creeping and saltating sand grains and their particle size characteristics at various heights, which led to the following conclusions: (i) the creeping masses increased as a power function (q = ?1·02 + 14·19u_*³) of friction wind velocities, with a correlation (R²) of 0·95; (ii) the flux of aeolian sand flow decreases exponentially with increasing height (q = a exp(–z/b)) and increases as a power function (q = ?26·30 + 428·40 u_*³) of the friction wind velocity; (iii) the particle size of creeping sand grains is ca 1·15 times of the mean diameter of salting sand grains at a height of 0 to 2 cm, which is 1·14 times of the mean diameter of sand grains in a bed; and (iv) the mean diameter of saltating sand grains decreases rapidly with increasing height whereas, while at a given height, the mean diameter of saltating sand grains is positively correlated with the friction wind velocity. Although these results require additional experimental validation, they provide new information for modelling of aeolian sand transport processes.     

PETROLEUM GEOLOGY

正20140890 Bai Ru(National Key Laboratory of Continental Dynamics,Department of Geology,Northwest University,Xi’an 710069,China);Zhang Jingong Characteristics of Pore Character and Its Controls of Chang 6Reservoir of Zhiluo Oilfield(Journal of Northwest University,ISSN1000-274X,CN61-1072/N,     

南黄海辐射沙洲主要潮沟的变迁

利用1966年和1977年海图、1995年和2000年合成孔径雷达影像,结合1980年以来的陆地卫星影像和2000年的岸滩实测剖面资料对南黄海辐射沙洲区主要潮沟的位置进行了解译与分析,得出上述4个时期研究区内主要潮沟深泓线位置图。对不同时期潮沟深泓线位置图进行几何校准与叠加,对比潮沟深泓线的迁移。结果表明：潮沟具有往返周期性摆动的特点,短期摆动速度明显快于长期摆动,主沟槽最大变动速度达127m／a,而支沟槽变动速度更大。潮沟摆动与沙洲变化有明显的相关性,但两者间的关系较为复杂。辐射沙洲目前处于破碎、萎缩阶段,除沙洲中心及陆岸岸滩仍有淤积外,大部分沙洲处于侵蚀状况,同时沙洲有整体向陆迁移的趋势。     

Evolution of an advancing gravel front: observations from Vedder Canal,British Columbia

Channelization of the lowermost part of Vedder River in 1922 initiated a natural experiment relevant to the unresolved question of how abrupt gravel–sand transitions develop along rivers. The new channel (Vedder Canal) had a fine bed and a much lower slope than the gravel‐bed river immediately upstream. Changes in morphology and sedimentology as gravel advanced into and along the Canal are documented using air photos, historical surveys, and fieldwork. The channel aggraded and steepened until stabilized by occasional gravel extraction in recent decades. The deposited material fines progressively along the Canal but the gravel front has retained an abrupt appearance because it has advanced by the sequential development of discrete gravel tops on initially sandy alternate bars. Near the gravel front the bed is highly bimodal and there is a sharper drop in the extent of gravel‐framework surface facies than in bulk gravel content. Ahead of the front, gravel is restricted to thin ribbons which often become buried by migrating sand. Calculations show that even though the gravel bed at the head of the Canal is almost unimodal, size‐selective transport during floods can account for the strong bimodality farther downstream. Copyright © 2011 John Wiley & Sons, Ltd.     

微生物沉积碳酸钙固化珊瑚砂的试验研究

向珊瑚砂中注入巴斯德芽孢杆菌菌液、氯化钙和尿素的混合液,利用微生物沉积碳酸钙固化珊瑚砂;并对珊瑚砂固化体进行了渗透、强度及微观结构等试验。试验结果表明,巴斯德芽孢杆菌的活性随时间呈衰减趋势,但衰减速度缓慢,能较好地满足珊瑚砂固化的需要。随着菌液、氯化钙和尿素的混合液注入次数的增加,珊瑚砂柱渗透性逐步降低,最终渗透性降低了1～2个数量级。微生物固化后的珊瑚砂柱应力-应变曲线大致可分为3段,即应力随应变缓慢增加段、快速增加段以及突降段。试样发生压裂脆性破坏,无侧限抗压强度最高达到14 MPa左右。抗压强度随干密度增加而增大,随渗透性降低而增大。微生物固化后珊瑚砂颗粒被生成的碳酸钙完整的包裹,孔隙间极少见生成的碳酸钙,与普通硅砂微生物固化后的微观结构不同,较好地解释了渗透性降低不多的原因。     

羌塘盆地那底岗日地区中侏罗世碳酸盐岩碳、氧、锶同位素与古海洋沉积环境

本文首次利用碳酸盐岩C,O,Sr稳定同位素探讨了羌塘盆地那底岗日地区中侏罗世海洋沉积环境的演变。测试结果表明,该区中侏罗世碳酸盐岩δ     

全球主要河流流域碳酸盐岩风化碳汇评估

碳酸盐岩风化吸收的大气CO₂主要以HCO₃ ^-形式连续地经由河流从大陆输送到海洋,成为陆地生态系统的重要碳汇。目前主要河流流域的碳酸盐岩风化碳汇估算存在不确定性,分布格局尚不清晰。基于GEMS-GLORI全球河流数据库提供的全球10万km ²以上主要河流流域多年平均监测数据,利用水化学径流法估算出全球主要河流流域碳酸盐岩对CO₂的吸收速率为0.43±0.15 Pg CO₂ yr ^-1,平均CO₂吸收通量为7.93±2.8 t km ^-2 yr ^-1。CO₂吸收通量在不同气候带下差异显著,热带和暖温带CO₂年吸收速率占全球主要河流流域年吸收速率的62.95%。冷温带CO₂年吸收速率占全球主要河流流域的33.05%,仅次于热带地区。本文划分出全球CO₂吸收通量的9个关键带,关键带的交汇处CO₂吸收通量较高。喀斯特出露流域碳酸盐岩对CO₂吸收通量的均值为8.50 t km ^-2 yr ^-1,约为非喀斯特流域的3倍。全球喀斯特出露流域碳酸盐岩风化碳汇在全球碳循环、水循环及碳收支平衡估算研究方面占据重要地位。     

砂井联合水泥土搅拌桩复合地基固结解析解

砂井联合水泥土桩复合地基是一种新型的复合地基加固技术,既可以加快软土地基固结时间,又可以增强软土地基的强度。针对该组合型复合地基的布桩特点,该类复合地基可以简化成以水泥土搅拌桩为中心的轴对称固结模型,并假定孔隙水沿径向渗流到砂井体内的流量等同于砂井体内排出的水量,考虑砂井的涂抹效应,推导出该类型下砂井联合水泥土搅拌桩复合地基固结方程。根据实际工程荷载多数单级施加和地基附加应力呈梯形分布的特点,得出了砂井联合水泥土桩复合地基固结解析解。通过对单级荷载情况下的复合地基固结解析解的退化,得出了瞬时施加荷载下的解析解。最后分别针对井径比、加荷历时、桩-土模量比、砂井渗透系数等影响因素,对复合地基固结性状进行了分析。该解答对提高此类复合地基的设计和计算水平有一定的理论指导意义。     

Laboratory Study on the Hydraulic Conductivity and Pore Pressure of Sand-Silt Mixtures

The hydraulic conductivity plays a major role on the excess pore pressure generation during monotonic and cyclic loading of granular soils with fines. This paper aims to determine how much the hydraulic conductivity and pore pressure response of the sand-silt mixtures are affected by the percentage of fines and void ratio of the soil. The results of flexible wall permeameter and undrained monotonic triaxial tests performed on samples reconstituted from Chlef River sand with 0, 10, 20, 30, 40, and 50% nonplastic silt at an effective confining stress of 100 kPa and two relative densities (D_r = 20, and 91%) are presented and discussed. It was found that the pore pressure increases linearly with the increase of the fines content and logarithmically with the increase of the intergranular void ratio. The results obtained from this study reveal that the saturated hydraulic conductivity (k) of the sand mixed with 50% low plastic fines can be, on average, four orders of magnitude smaller than that of the clean sand. The results show also that the hydraulic conductivity decreases hyperbolically with the increase of the fines content and the intergranular void ratio.