Middle Cretaceous pCO2 Variation in Yumen,Gansu Province and its Response to the Climate Events

The palaeo-atmospheric CO_2 concentration(pCO_2) variation in the Yumen, Gansu Province during the middle Cretaceous has been reconstructed using the newly established plant photosynthetic gas exchange mechanistic model, and the results show that the p CO_2 values are in the range of about 550–808 ppmv. The present pCO_2 values are higher than the p CO2 results(531–641 ppmv) of the previous study according to the Recent standardization of the stomatal ratio method, and much lower than the pCO_2 results(882–1060 ppmv) according to the Carboniferous standardization of the stomatal ratio method. The present pCO_2 variation is not only within the error range of GEOCARBⅡ and GEOCARB Ⅲ but also is similar to the reconstructed results based on the biochemistry and carbon isotope models. Besides, the present Brachyphyllum specimens were collected from four consecutive horizons of the upper Zhonggou Formation of the Hanxia Section, and the reconstructed pCO_2 exhibits the reconstructed pCO_2 exhibits a decline trend during the late Aptian to early Albian. This decline variation is probably associated with the Oceanic Anoxic Events(OAE1 b) and the Cold snap event. With the combination of p CO_2 during the Albian to Cenomanian recovered by the plant photosynthetic gas exchange mechanistic model, the pCO_2 showed a prominent increase during the late Aptian to early Cenominian, which indicates a response to the greenhouse warming during the middle Cretaceous. Therefore, the mechanical model of the plant photosynthetic gas exchange shows a relatively strong accuracy in the reconstruction of the pCO_2 and can reflect a strong relation between the atmospheric CO_2 concentrations and climatic events.     

琼东南盆地东部层间断层系及其形成机制分析

基于琼东南盆地最新3D地震资料的地质与地球物理解释,运用先进的地震剖面相干处理技术,在琼东南盆地东部早-中中新世泥岩中发现了大量层间断层,这些断层剖面上为板状正断层,倾角一般大于45°,长度不超过1000m,但是平面走向在不同区域差异很大。研究区层间断层为以体积收缩机制为主要形成机制,在区域应力、重力滑塌和超压水力破裂多种力学机制共同影响下形成的,基本限制在层间的、多种类型和多种性质的断层组合。研究区东北部主要为体积收缩机制形成的层间断层,并受到重力滑塌的影响,断层主要表现为平行于等深线的EW向的断层密集带和与之垂直的SN向直线状断层;中部主要受超压水力破裂作用和体积收缩机制的影响,断层主要由放射状断层和与之垂直的层间断层两部分组成;西南部地区主要受体积收缩作用和区域应力场的影响,在构造断层影响区,层间断层走向与构造断层相互垂直,未影响区则表现为断层多边形。     

Study on Fractal Feature of Fault Structure and Its Geological Implications Based on Remote Sensing——A Case Study of Jiuyi Mountain Area, Southern Hunan

以九嶷山地区ETM+遥感影像数据为信息源,通过信息提取与解译快速获取该区断裂构造.运用分形理论的盒维数法对断裂构造体系进行分形研究,结果表明,区内断裂构造在0.05～2.75km尺度范围内具有良好的自相似性和分形特征,总体分维值D=1.1155、R2=0.9964,分维值接近中国大地构造单元稳定区分维值;不同走向断裂分维值D在0.9184～1.0441间、R2介于0.9983 ～0.9996间,各分维值D不仅定量描述了各走向断裂分布的复杂性和构造演化的成熟度,而且还反映了断裂的成矿作用:NE向断裂分维值最大,D值在1.0441附近时主要表现为导矿构造;SN向断裂分维值次之,D在0.9870附近时主要表现为控矿构造;NW向断裂分维值偏小,D在0.9502附近时主要表现为含矿构造.     

中南地区地质调查中北斗卫星技术应用研究

主要介绍了基于北斗卫星的野外地质调查系统在丛峦叠障、植被覆盖茂密的中南地区野外地质调查中应用的情况,包括野外作业管理、人员安全保障以及遥感异常查证等。试验结果显示,利用该系统基本可实现野外地质调查人员的实时地理位置显示、历史轨迹回放、态势分析以及路线规划等;试验区内系统的通讯基本通畅,可以实现终端与终端、终端与指挥机之间的双向短报文通讯;利用北斗系统的定位功能,可实时记录异常查证点信息,对室内解译的遥感成果进行及时调整和修改,提高了野外地质调查的工作效率。      

冻结黏土空心圆柱试样制样方法

冻土空心圆柱仪是室内研究冻土在车辆荷载等复杂应力路径下力学特性的主要仪器,试验中为实现主应力轴方向在垂直于径向平面内连续旋转,其试样多采用薄壁空心圆柱试样,但由于空心圆柱试样薄壁的特点,增加了制样的困难,成为制约冻土空心圆柱试验研究进展的主要阻碍。为此,借鉴冻土三轴试验的制样方法,基于实验室现有的制样条件,设计了一套重塑冻结黏土空心圆柱试样的制样装置,可提高制样效率,减小制样过程中人为因素的影响;随后,基于该制样装置,提出了一种冻结黏土空心圆柱试样的制样方法,给出了制备重塑冻结黏土的制样步骤。最后,通过对所制备试样的物理力学性质测定,发现采用该制样方法可以制备含水率及干密度均匀、力学性质稳定的重塑冻结黏土试样;同时对两个平行制备的冻结黏土试样的不同主应力轴方向的定向剪切试验结果进行了比较,证明了所提出的制样方法具有良好的可重复性,且所得的冻土力学特性与已有研究成果吻合较好,可用于进一步系统研究复杂条件下冻结黏土的静、动力学特性。     

Carbon Geochemistry of Gas Hydrate‐associated Sediments in the Southwestern Taiwan Basin

Marine gas hydrates, one of the largest methane reservoirs on Earth, may greatly affect the deep sea sedimentary environment and biogeochemistry; however, the carbon geochemistry in gas hydrate-bearing sediments is poorly understood. In this study, we investigated the carbon variables in sediment core 973-3 from the southwestern Taiwan Basin in the South China Sea to understand the effect of environmental factors and archaeal communities on carbon geochemistry. The carbon profiles suggest the methanogenesis with the incerase of dissolved inorganic carbon(DIC) and high total organic carbon(TOC)(mean = 0.46%) originated from terrigenous organic matter(mean δ~(13)C_(TOC) value of-23.6‰) driven by the abundant methanogen ‘Methanosaeta and Methanomicrobiales'. The active anaerobic oxidation of methane is characterized by the increase of DIC and inorganic carbon(IC), and the depleted δ~(13)C_(IC), coupled with the increase of TOC and the decrease of δ~(13)C_(TOC) values owing to the methanotroph ‘Methanosarcinales/ANME' in 430–840 cm. Environmental factors and archaeal communities in core 973-3 are significantly correlated to carbon variables owing to methane production and oxidation. Our results indicate that the carbon geochemical characteristics are obviously responding to the formation and decomposition of gas hydrates. Furthermore, pH, Eh and grain size, and Methanosaeta greatly affect the carbon geochemistry in gas hydrate-associated sediments.     

桂林市乌金河流域污染分析

通过对乌金河流域点污染源的实测与面污染源的估算,初步确定点面污染源排污总量,并用单项超标法、等标污染负荷法对乌金河流域的水质进行评价,分析了流域的污染特征,同时对如何防治水污染提出了一些看法。     

南天山库车秋里塔格褶皱带三维构造分析

笔者利用库车秋里塔格地区3000km的二维地震反射资料，结合地表构造测量成果，分段叙述秋里塔格褶皱带的构造几何学和运动学性质，说明构造交汇部位断层和褶皱的叠加过渡关系，并通过二维构造剖面的组合，建立秋里塔格褶皱带的三维构造几何模型。研究发现秋里塔格褶皱带为浅部断层传播褶皱与深部断层转折褶皱叠加形成的复合型背斜带，深部台阶状逆断层的叠加作用、叠加断层位移量的转换、断层断坡高度的变化造成地表背斜沿走向发生变化，笔者通过测量断层叠加方式、断层位移量转换、断层断坡高度，说明秋里塔格褶皱带背斜叠加、扭曲、分叉现象的构造机理，并且给出了秋里塔格褶皱带断层的滑移量。     

陆气耦合模型在实时暴雨洪水预报中的应用

采用加拿大区域性中尺度大气模式MC2(Canadian Mesoscale Compressible Community)和新安江模型单向耦合模型系统,对2005年7月4～15日发生在淮河流域的一场暴雨洪水,进行了实时预报.采用王家坝以上流域的实测降水和王家坝断面的实测洪水资料,对MC2预报降水的时空分布和陆气耦合模型预报的洪水过程进行了分析.结果表明,MC2对该场强降水过程具有很好的预报能力,陆气耦合模型有效地增长了洪水预报的预见期,具有很好的应用前景.     

中天山白石头泉岩体年代学、岩石成因及构造意义

白石头泉岩体位于中天山北缘边界断裂(沙泉子断裂)南侧。该岩体从下至上可分为五个连续过渡的岩相带,即淡色花岗岩(a带),含天河石花岗岩(b带),天河石花岗岩(c带),含黄玉天河石花岗岩(d带)以及黄玉钠长花岗岩(e带),其中,b、c、d和e带均为a带分异的产物。白石头泉岩体的LA-ICP-MS锆石U-Pb定年结果表明,该岩体侵位于早二叠世早期(295.6±1.3Ma),并于印支期(~214Ma)经历了一次热事件的改造。淡色花岗岩在主量元素上富硅(SiO₂= 74.93%~76.18%)、富碱(K₂O + Na₂O=8.07%~8.80%)、富钠(K₂O / Na₂O=0.82~0.89),贫钙、镁,而在微量元素上富Rb、F和Ga(Al/Ga比值为2217~3134),贫Ba、Sr和Eu并具强烈的铕负异常(δEu=0.0020~0.0091),反映出其源区为富含白云母的片岩(或片麻岩),成岩压力较低,温度大于860℃。结合区域地质特征,作者等认为白石头泉岩体形成于相对拉张的构造背景,是中-上地壳源岩经历高温贫水熔融的产物,其形成与幔源岩浆内侵作用有关。