兰州第四纪黄土/古土壤序列物源演变: 来自于碳酸盐矿物的证据*

黄土/古土壤的物源研究对于揭示第四纪气候变化和青藏高原隆升历史具有重要意义。本研究以位于黄土高原西部1.4 Ma以来的兰州黄土/古土壤沉积序列为研究对象,基于X射线衍射技术分析了黄土/古土壤中的主要矿物组成,侧重于碳酸盐矿物含量,追溯了兰州黄土/古土壤的直接物源。结果显示: (1)1.4 Ma以来兰州地区黄土/古土壤沉积物的主要直接源区为柴达木盆地沙漠区和阿拉善干旱区。(2)基于二元混合模型计算的潜在原始源区对兰州黄土白云石和总碳酸盐矿物的相对贡献率以及长石与石英比值结果一致支持1.4 Ma以来兰州黄土原始物源发生了多次变化。1.4~1.1 Ma和0.9~0.3 Ma青藏高原东北缘造山带(昆仑山、祁连山)和中亚造山带对兰州黄土的贡献相当,而1.1~0.9 Ma和0.3 Ma以来,中亚造山带对兰州黄土的物源贡献增加,这可能分别是对中更新世气候转型和0.3 Ma以来青藏高原及邻近地区干冷气候增强的响应。1.15 Ma和0.8 Ma兰州黄土/古土壤中高的白云石含量、碳酸盐矿物总含量以及0.8 Ma长石与石英比值的快速升高可能是对“昆黄运动”的响应,进而造成了昆仑山、祁连山对黄土高原物源贡献的增加。     

计算域的选取对风暴潮数值模拟的影响

作者以 72 0 3号台风过程中引起的黄海沿岸水文测站的风暴潮过程为例 ,选取不同计算域 ,模拟计算的同一测站的风暴潮增水值有很大差异。只有选取整个黄渤海海域 ,才能得到较精确的风暴潮增水结果。从而揭示在封闭或半封闭海域中由风暴过程激发的区域自由振荡 ,是风暴潮增水中不容忽视的量。说明该海域中的风暴潮过程是海域整体效应的响应 ,因此认为数值模拟中计算域应选取整个封闭或半封闭海域     

Three-dimensional modeling of bank erosion and morphological changes in the Shishou bend of the middle Yangtze River

This paper presents a three-dimensional (3-D) numerical model to simulate morphological changes in alluvial channels due to bank erosion. A method for the simulation of bank erosion is established. This is incorporated into a 3-D mathematical model for turbulent flow and non-uniform, non-equilibrium sediment transport. This model is applied to simulate morphological changes in the Shishou bend of the middle Yangtze River in China, where serious bank erosions occurred during the last two decades. The double-layer sediment structure of the riverbank on the middle Yangtze River is taken into account in the bank erosion module. Both cohesive and non-cohesive bank material in the different layers are considered. The bank erosion module also includes other factors affecting the rate of bank erosion, such as the longitudinal length of failed bank, the thickness of each layer in the double-layer structure, and the erosion-resisting effect of cohesive material from the top layer of failed bank. A locally-adaptive grid system is proposed to efficiently simulate the lateral migration of alluvial channel due to bank erosion. The predictive capability of the 3-D model is examined by laboratory data. Simulated processes of bank erosion agree with field observations in the Shishou bend during the period of October 1996–October 1998, and the bank erosion module plays a significant role in simulating morphological changes of the study reach. In addition, the equivalent channel-forming discharge, which is defined as a constant discharge that can create the same amount of bank erosion in an alluvial channel as that created by natural runoff processes during the same period of time, is proposed to improve calculation efficiency for feasibility studies.     

不同方案求解非线性化学动力学方程组的比较

在一个简化的气相化学模式的基础上,比较了Hybrid、QSSA、Sklarew三种计算方案求解非线性化学动力学方程组的差异,并引入误差分配和线性组合两种质量守恒技术,分析它们对模拟结果的影响。研究结果表明：不同方案对有机烃类浓度的计算几乎没有影响,但对其它气态物浓度有一定的影响。用QSSA和Slarew方案预测的结果更为相近,而采用Hybrid方案得到的气态物浓度的平衡时间略为提前。从计算效率来看,QSSA方案优于其它两种方案,两种质量守恒技术均能改善模拟结果。     

A New Approach for Studying Hubble Diagrams of Quasars

In this paper, a new approach for studying Hubble diagrams of quasars is introduced. The purpose is to reduce the well-known very large scatter in the diagram. We believe that the scatter is mainly caused by the wide spread of luminosity distribution of quasars. Based on a large number of quasars having been discovered, we introduce a new quantity, the collective apparent magnitude of certain amount of quasars in a corresponding redshift interval, and make a plot of the collective apparent magnitude versus redshift with the data published by Hewitt and Burbidge (1993). The quantity is contributed by individual apparent luminosities as well as the luminosity distribution of quasars. Scatter is expected to be largely reduced in the corresponding diagram, and this is indeed true as shown by the figures. By discussing several possible effects and from the figures, we find that the assumption that redshifts of quasars are distance indicators is confirmed, and the standard cosmological model is supported. This revised version was published online in July 2006 with corrections to the Cover Date.     

内蒙古西乌旗地区下二叠统寿山沟组烃源岩有机地球化学特征

近些年二连盆地及外围地区石炭—二叠系油气研究工作表明该区具有很大的勘探潜力,西乌旗下二叠统寿山沟组为该区油气勘探的重要目的层之一。为了更准确、深入地认识寿山沟组烃源岩的品质,本文针对寿山沟组烃源岩样品进行有机地球化学特征方面的研究。通过总有机碳（TOC）测试、氯仿沥青及族组分抽提分离、生油岩热解分析、饱和烃GC-MS测试手段重点对烃源岩进行有机质丰度、成熟度及类型评价,并根据有机分子地球化学特征判识生烃母质来源及其沉积环境。研究结果表明：样品总有机碳含量（TOC）均值为1.01%,氯仿沥青“A”含量均值为0.23%,生烃潜量PG（S₁+S₂）均值为0.05×10^-3,综合判识烃源岩有机质丰度为“中等—较好”级别;样品Ro值较高,介于1.67%~4.36%,结合Ts/（Ts+Tm）值与C₂₉甾烷异构化参数特征综合判断有机质成熟度达“高成熟—过成熟”阶段;生物标志物分析结果表明烃源岩的生烃母质以低等浮游生物、菌藻类为主,陆生高等植物为辅,有机质类型为Ⅱ₁、Ⅱ₂型;古水体盐度较高,有机质保存于还原性条件。综合有机质丰度、类型、成熟度、保存条件各项参数认为西乌旗地区寿山沟组烃源岩可达“中等—较好”级别,可为研究区油气资源富集提供气源。

     

准噶尔盆地南缘中-新生界碎屑成份特征与构造期次

准噶尔盆地南缘晚侏罗世-早白垩世早期、晚白垩世及晚新生代发育的近源粗碎屑沉积显示构造活动的存在。野外剖面及镜下碎屑成份统计表明:砾岩的砾石成份、砂岩碎屑成份的物源属性主要是再旋回造山带和晚古生代的岩浆弧,但盆地南缘东段与西段的岩屑组成及物源属性存在较大的差异。其中,沉积岩岩屑在晚侏罗世—早白垩世早期、晚白垩世和晚新生代发生了相应的增加,显示盆缘沉积岩物源的隆升—剥蚀作用和构造活动的相对活跃。砂岩碎屑特征、重矿物相对含量及重矿物组合特征证明盆地南缘东、西两段的物源属性存在较大差异,特别是不稳定重矿物的增加显示晚侏罗世-早白垩世早期、晚白垩世和晚新生代为构造相对活跃的构造环境。综合中-新生界沉积碎屑特征及差异分析,准噶尔盆地南缘中-新生代盆山格局发生了3次较大的转变过程,分别对应于上述3个时期。中-新生代3次构造活动对含油气系统形成具有重要控制作用,构造活动期次与油气藏形成、调整的期次也有良好的对应关系。     

陆相地层的层序地层学:层序的特征与模式

陆相地层的层序地层学研究近年来取得了较大的进展,尤其在层序的组成、层序界线和最大洪泛面的识别以及层序模式的建立等方面研究得比较深入。层序地层的组成包括层序组合和层序的内部单元。层序界线和最大洪泛面的识别是陆相地层层序地层学研究的关键。目前已初步建立了箕状断陷盆地、坳陷盆地以及冲积地层背景的层序模式。     

1995年世界气候概况

１９９５年，世界气候普遍偏暖。欧亚大陆大部、北美大陆中部、南美大陆中部、非洲西北部的年平均气温大多偏高１－２℃，其中俄罗斯大部、美国西南部显著偏高，部分地区偏高４℃，北半球中高纬度地区冬暖非常显著。由于北半球中纬度地区，许多测站气温高达３５－４０℃，为近几十年乃至百年一遇。年内，全球许多地区旱涝频繁，诸如年初欧洲的暴风雪与美国加利福尼亚洲的特大洪水及夏季朝鲜、与中南半岛的大水灾、加勒比海的飓风等危