南海北部ODP 1144站中更新世气候转型期有孔虫稳定同位素古气候意义     

金海燕  翦知湣 《地球科学进展》2007,22(9):914-921

中更新世气候转型期是第四纪古气候研究的一个特殊时期。利用大洋钻探ODP 184航次在南海北部钻取的1144站时间分辨率高达约290年的沉积物样品，开展中更新世气候转型期古气候变化的研究。在中更新世距今80~100万年前，浮游和底栖有孔虫壳体的稳定氧碳同位素变化揭示出，中更新世气候转型中心，即中更新世革命0.9 Ma左右，南海北部表层海水温度的降低和降水量的增加指示东亚冬、夏季风增强。以中更新世革命为界，水体垂向结构上温跃层和营养跃层的深度从之前的间冰期较浅转变为之后的间冰期较深，底层水与表层水的垂直温度梯度从冰期时较大转变为冰期时较小。轨道尺度上，冰消期时南海北部的表层水、次表层水和底层水的变化几乎是同时发生的，不存在超前或滞后的相位差。千年尺度上，有孔虫的氧碳同位素变化都呈现出非常明显的约0.8 ka和约1.4 ka的气候波动周期。氧同位素0.8 ka滤波显示出：在中更新世气候转型期，较强的信号主要出现在间冰期，有时也出现在冰期，与晚第四纪千年尺度气候波动主要出现在冰期不同，说明中更新世的气候转型不仅表现在轨道尺度的气候周期变化上，同时也体现在千年尺度气候波动的特征变化中。   相似文献   

寒武系崮山阶三叶虫生物地层新认识   总被引：1，自引：0，他引：1  

朱兆玲  项礼文  章森桂  刘书才  雒昆利  杜圣贤  梁宗伟 《地层学杂志》2007,31(2):165-168

由于Diceratocephalus已在华北的若干地点找到,如莱芜九龙山、淄博黑石寨和泰安大汶口,Dicerato-cephalus三叶虫亚带可以提升为三叶虫带,这样崮山阶便包含了4个三叶虫带(自上而下)Diceratoceph alusarma-tus带、Drepanura premesnili带、Blackwelderia paronai带和Damesella paronai带。  相似文献   

华南中生代构造演化过程的多地质要素约束——湘东南及湘粤赣边区中生代地质研究的启示   总被引：18，自引：11，他引：18  

柏道远  黄建中  李金冬  王先辉  马铁球  张晓阳  陈必河 《大地构造与成矿学》2007,31(1):1-13

目前对华南内陆中生代构造环境与演化过程的认识存在分歧,一定程度上与对多种地质要素的综合研究不够有关。笔者研究认识到湘东南及湘粤赣边区中生代不同构造阶段发育不同的代表性地质要素,并分别指示不同的构造环境。早三叠世-中三叠世早期为前造山阶段,主要发育海相沉积。中三叠世后期-中侏罗世初为陆内造山阶段,其中中三叠世后期发生强烈陆内汇聚挤压,形成的主要地质要素是NNE向的逆冲断裂与褶皱,以及NW向的基底走滑断裂等;中三叠世末-晚三叠世后期为同造山阶段的后碰撞构造环境,形成的主要地质要素是印支期强过铝花岗岩;晚三叠世末-早侏罗世为同造山上隆伸展环境,形成的主要地质要素是裂陷盆地与拉斑玄武岩;中侏罗世初期为挤压环境,形成的主要地质要素是山前冲断收缩盆地及盆地边缘的逆冲断裂。中侏罗世早期-晚侏罗世为后造山阶段,形成的主要地质要素是大量后造山花岗岩以及与花岗岩相关的大量有色金属矿床。白垩纪为陆内裂谷阶段,形成的代表性地质要素有AA型花岗岩、大量陆相红色断陷盆地、基性火山岩、双峰式次火山岩等。结合上述成果和区域资料,提出应通过多种地质要素综合研究华南地区中生代构造演化过程,注意构造环境判别的地质要素代表性、地质要素时限性以及构造发展过程的关联性。  相似文献   

Distribution, migration and derivation of Mesozoic-Cenozoic regional fault systems in the central continental margin of eastern China     

Sun Xiaomeng  Hao Fujiang  Bian Weihua  Gao Yi  Bao Yafan 《Frontiers of Earth Science》2007,1(1):12-20

Deep-large faults in the central continental margin of eastern China are well developed. Based on the regularity of spatial and temporal distribution of the faults, four fault systems were divided: the Yanshan orogenic belt fault system, the Qinling-Dabie-Sulu orogenic belt fault system, the Tanlu fault system and the East China Sea shelf basin-Okinawa trough fault system. The four fault systems exhibit different migration behaviors. The Yanshan orogenic belt fault system deflected from an EW to a NE direction, then to a NNE direction during the Indo-Chinese epoch-Yanshanian epoch. The thrust-nappe strength of the Qinling-Dabie orogenic belt fault system showed the tendency that the strength was greater in the south and east, but weaker in the north and west. This fault system faulted in the east and folded in the west from the Indo-Chinese epoch to the early Yanshanian epoch. At the same time, the faults also had a diachronous migration from east to west from the Indo-Chinese epoch to the early Yanshanian epoch. On the contrary, the thrust-nappe strength was greater in the north and west, weaker in the south and east during the late Yanshanian epoch-early Himalayan epoch. The Tanlu fault system caused the basin to migrate from west to east and south to north. The migration regularity of the East China Sea shelf basin-Okinawa trough fault system shows that the formation age became younger in the west. The four fault systems and their migration regularities were respectively the results of four different geodynamic backgrounds. The Yanshan orogenic belt fault system derived from the intracontinental orogeny. The Qinling-Dabie-Sulu orogenic belt fault system derived from the collision of plates and intracontinental subduction. The Tanlu fault system derived from the strike-slip movement and the East China Sea shelf basin-Okinawa trough fault system derived from plate subduction and retreat of the subduction belt. Translated from Journal of Jilin University (Earth Science Edition), 2005, 35(5): 554–563 [译自: 吉林大学学报 (地球科学版)]  相似文献   

Spatial pattern of Karst rock desertification in the Middle of Guizhou Province,Southwestern China   总被引：13，自引：0，他引：13  

Qiu-Hao Huang  Yun-Long Cai 《Environmental Geology》2007,52(7):1325-1330

Karst rocky desertification is a typical type of land degradation in the Southwestern China. It has great ecological and economical implications for the local people. Landsat images from the middle of Guizhou Province collected in 1974, 1993 and 2001 were used for change detection of the pattern of Karst rocky desertification. The results show the following findings: (1) Desertification area expanded drastically in 27 years, at an increasing rate about 116.2 km²/year. (2) High areas (900–1,500 m) are the most affected. (3) Areas with the slope <5° or >25° are also easily tend to be Karst rocky deserted. (4) The process of Karst rocky desertification is nearly irreversible. Few areas of Karst rocky desertification could be meliorated to non-desertification land. (5) Most of the degraded lands are located in the south and the central of the study region, and the meliorated land areas are sparsely located in the east and the west part of the region. All these findings would provide bases for the decision-making of the local government to improve the Karst rocky desertification  相似文献   

Vulnerability of groundwater in Quaternary aquifers to organic contaminants: a case study in Wuhan City,China   总被引：5，自引：0，他引：5  

Yanxin Wang  Broder J. Merkel  Yilian Li  Hui Ye  Surong Fu  Dana Ihm 《Environmental Geology》2007,53(3):479-484

More than 30 organic contaminants were detected in shallow groundwaters at Wuhan, the largest city in central China. Seriously contaminated groundwaters were from densely populated, industrial and commercial areas. Abnormal concentrations were found in groundwater from Hankou, downtown Wuhan: trimethylbenzene up to 29 μg/L, tetramethylbenzene up to 866 μg/L, and trichloroethene up to 9.5 μg/L. Benzene, Toluene, Ethylene and Xylene (BTEX) contamination of groundwater is serious and widespread at Wuhan, ranging between 0.14 and 25.0 μg/L. Considering the hydrogeological conditions of most Chinese cities, DRAMIC, a modified version of the widely used DRASTIC model, was proposed by the authors for assessing vulnerability of groundwater to contamination. The factors D, R, A and I in DRAMIC model are the same as in DRASTIC. The factor topography is ignored. The factor soil media is substituted by a new factor aquifer thickness (M) and the factor hydraulic conductivity of the aquifer by a new factor impact of contaminant (C). The equation for determining the DRAMIC Index is: DRAMIC = 5D _R + 3R _R + 4A _R + 2M _R + 5I _R + 1C _R. The calculated DRAMIC Index can be used to identify areas that are more likely to be susceptible to groundwater contamination relative to each other. The higher the DRAMIC Index is, the greater the groundwater pollution potential. Applying DRAMIC, a GIS-based vulnerability map for Wuhan city was prepared. Interestingly, places such as downtown Hankou, where enhanced concentrations of BTEX have been detected, correspond quite well with those with higher DRAMIC ratings.  相似文献   

Comparison of element abundance between the exposed crust of the continent of China and the global averaged upper continental crust: Constraints on crustal evolution and some speculations     

Wang Yang 《Frontiers of Earth Science》2007,1(1):69-79

Based on the results of a study of regional element abundance in eastern China and the 1:200 000 geochemical surveys in northern Xinjiang, the element geochemical characteristics of the exposed crust in 23 tectonic units of the continent of China are summarized. Compared with the global average abundance of the upper continental crust, the exposed crust of the continent of China is compositionally more evolved than the upper crust of the island arc, but less evolved than the mature Precambrian Canadian shield. The exposed crust of the North China and Yangtze platforms has a lower SiO₂ content, but markedly higher CaO and MgO contents due to the presence of widespread carbonate strata, which suggests that we should not neglect the contribution of carbonate rocks in the study of the exposed crust and the element abundance of the upper crust. In comparison with two recently published average compositional models of the global upper continental crust, the exposed crust of the continent of China is depleted in Au, Hg, Mo, Sn, and W, which suggests that their abundance in the present global models is overestimated. The exposed crust of the North China platform and the Qinling-Dabieshan fold belt to its south has lower μ(²³⁸U/²⁰⁴Pb) values (<8), but other regions of the continent of China exhibit much higher μ values, which implies that the low μ feature of the North China platform and its adjacent regions does not have global significance. Considering the apparent lateral variation in composition of the exposed crust for the tectonic units of the continent of China, there is no adequate reason to take the average upper crust compositional model of the North China platform and its adjacent regions as a reliable composition representative for Chinese and global upper continental crust composition. Translated from Geological Bulletin of China, 2005, 24(10–11): 906–915 [译自: 地质通报]  相似文献   

Environmental impact assessment of risk associated with groundwater overdraft remediation in cone of depression,Jining, China     

B. T. I. Ong′or  Long-cang Shu  Pei-gui Liu 《Environmental Geology》2007,53(4):751-762

In this paper, a simple scenario and probabilistic approach is used to assess the potential groundwater risk due to proposed overdraft remedial actions in cone of depression, Jining City, China. Focusing on the concentrations of Chloride ions (Cl⁻) and total hardness (TH), the impact of artificial recharge and reduced pumping on groundwater quality and quantity is analysed by using the three-dimensional finite difference groundwater flow and transport model, Visual MODFLOW, to simulate groundwater flow and transport within the study area based on scenarios, and utilizes SURFER software to map risk levels. Although 5, 10 or 15% reduced pumping with artificial recharge leads to more decrease in Cl⁻ and TH concentrations than the 25%, less volume increase is achieved for the remediation of land subsidence and other environmental problems in the cone of depression. The Cl⁻ concentrations in recovered groundwater are within the desired concentration of 200 mg/l; however, TH in some cases are above the maximum permissible limit of 500 mg/l, with an exceedence probability of about 0.67 for recharge and recharge with reduced pumping at 25%. The presence of fractures and hydrogeological complexity greatly determines impacts of remediation, and the 22% reduced pumping with artificial recharge offers an optimum strategy for overdraft remediation in the Jining cone of depression.  相似文献   

Potential hyperaccumulation of Pb, Zn, Cu and Cd in endurant plants distributed in an old smeltery, northeast China   总被引：1，自引：0，他引：1  

Shuang Cui  Qixing Zhou  Lei Chao 《Environmental Geology》2007,51(6):1043-1048

The absorption and accumulation of Pb, Zn, Cu and Cd in some endurant weed plant species that survived in an old smeltery in Liaoning, China, were systematically investigated. Potential hyperaccumulative characteristics of these species were also discussed. The results showed that metal accumulation in plants differed with species, tissues and metals. Endurant weed plants growing in this contaminated site exhibited high metal adaptability. Both the metal exclusion and detoxification tolerance strategies were involved in the species studied. Seven species for Pb and four species for Cd were satisfied for the concentration time level standard for hyperaccumulator. Considering translocation factor (TF) values, one species for Pb, seven species for Zn, two species for Cu and five species for Cd possessed the characteristic of hyperaccumulator. Particularly, Abutilon theophrasti Medic, exhibited strong accumulative ability to four heavy metals. Although enrichment coefficients of all samples were lesser than 1 and the absolute concentrations didn’t reach the standard, species mentioned above were primarily believed to be potential hyperaccumulators.  相似文献   

A New Specimen of Liaoceratops yanzigouensis (Dinosauria: Neoceratopsia) from the Early Cretaceous of Liaoning Province, China          下载免费PDF全文

YOU Hailu  Kyo TANOUE  Peter DODSON 《《地质学报》英文版》2007,81(6):898-904

A new specimen of basal neoceratopsian dinosaur Liaoceratops yanzigouensis is described. The specimen comes from the Lujiatun Bed of the Lower Cretaceous Yixian Formation in Beipiao City of western Liaoning Province, and is represented by a very well preserved three-dimensional partial skull and mandible. It is also the smallest among the three specimens of L. yanzigouensis, and several features in the new specimen, such as the short preorbital length and the round rostroventral orbital rim, can be ontogenetically-related. The superb exposure of the palatal complex may be caused by the removing of its brain by a small predator in the contemporary Jehol Biota.  相似文献