Discussion on evolution of Min Jiang River: Heavy mineral evidence from the Quaternary fluvial sediments in Yibin area,Sichuan Province          下载免费PDF全文

Li Lei  Xiang Fang  Liu Yi-Ming  Tai Zi-Han 《古地理学报》1999,22(4):761-774

Heavy minerals deposited on river terraces can be used to reflect source rock properties and reveal river evolutionary processes. This study focused on the heavy minerals deposited in the lower Min Jiang River terraces and in the modern deposits. We studied paleo-current direction, characteristics of the heavy mineral assemblages, characteristic metamorphic minerals and heavy mineral characteristic indices. The results show that the lower reaches of the Min Jiang River Ⅴ- to Ⅲ-level terrace deposits consist dominantly of magmatic rock type, which mainly comes from the Longmen Shan mountain tectonic belt. The heavy minerals deposited in modern sediment come from the Songpan-Ganzi fold belt. The heavy mineral characteristic indices suggest that this change is due to headward erosion of the Min Jiang River. Affected by the phase B of the Kunhuang movement, the Min Jiang River was incised to the Wenchuan area at 0.73-0.7 Ma and the Ⅴ-level terrace formed. The Min Jiang River was strongly cut down at 0.5-0.3 Ma due to the phase C of the Kunhuang movement, and as a result the Ⅳ-level terrace formed. Influenced by Gonghe movement, the Min Jiang River was incised to the stone mark and Ⅲ-level terrace formed in 0.11-0.09 Ma. After that, the modern Min Jiang River was formed at around 27 ka.  相似文献   

Three-dimensional analysis of groundwater flow in neogene rocks at the Rokkasho low-level radioactive waste disposal center, Japan     

Tai Sasaki  Naro Hashimoto  Takayuki Nakato  Tomonari Shiraishi  Kazuaki Yajima  Tomoyuki Hishiya 《Engineering Geology》1998,49(3-4):337-343

As a preliminary step for predicting groundwater flow in a plateau 30–50 m above sea level, a model for three-dimensional analysis of groundwater flow was formulated and its validity was verified. The plateau consists of Neogene sedimentary rocks and a Quaternary deposit. Most of the groundwater originates in precipitation, with the groundwater table lying in the Quaternary deposit. Steady-state analysis was conducted by using the finite element method. The results of pore-water pressure measurement and water examination were useful in verifying the validity of the model. In constructing the model, reducing the hydraulic conductivity according to the depth on the basis of the results of the actual measurement was important.  相似文献   

中国粮食总产量结构分析与丰歉评估   总被引：12，自引：3，他引：9  

王建林  太华杰 《气象》1998,24(12):7-12

对中国粮食总产量的结构分析表明：①粮食作物平均单产的变化在粮食总产量的变化中约占２／３以上,起着决定性的作用;②５０年代以来,小麦,玉米产量在粮食总产量中的份额呈增加之势,而水稻所占份额相对稳定,大豆等其它作用的份额则有下降趋势;③就主要粮食作物单产而言、一季稻的产量为最高,小麦产量的增长为最快。通过分析中国粮食作物平均单产的丰歉与气象条件的关系发现;西北和东北地区的降水量,华北地区的积温与产量丰  相似文献   

世界重大地质灾害地震的平面和深度分布概况     

季泰 《城市地质》2008,3(3):51-52

该文简要介绍了世界主要地震带的分布区域和历次地震所造成的巨大损失,介绍了地震的深度分布范围及成因类型。  相似文献   

Sources and Exchange of Particulate Organic Matter in an Estuarine Mangrove Ecosystem of Xuan Thuy National Park, Vietnam     

Nguyen Tai Tue  Tran Dang Quy  Hideki Hamaoka  Mai Trong Nhuan  Koji Omori 《Estuaries and Coasts》2012,35(4):1060-1068

The spatio-temporal variations in stable isotope signatures (??¹³C and ??¹⁵N) and C/N ratios of particulate organic matter (POM), and physicochemical parameters in a creek water column were examined in an estuarine mangrove ecosystem of Xuan Thuy National Park, Vietnam. The objective was to examine the factors influencing creek water properties, and the sources and exchange of POM in this important mangrove ecosystem. The diel and seasonal variations in water temperature, flow velocity, pH, dissolved oxygen, and salinity demonstrated that tidal level, season, and biological factors affected the creek water properties. Mangroves had relatively low ??¹⁵N and very low ??¹³C values, with respective average values of 1.5?±?0.9?? and ?28.1?±?1.4??. The low mangrove leaf ??¹⁵N indicated minor anthropogenic nitrogen loading to the mangrove forests. A significant positive correlation between POM?C??¹³C and salinity along the axis of Ba Lat Estuary, Red River, indicated that marine phytoplankton (??¹³C value, ?21.4?±?0.5??) was the predominant source of POM at the estuary mouth. Based on the co-variation of ??¹³C and C/N ratios, marine phytoplankton and mangrove detritus were predominant in POM of major creeks and small creeks, respectively. During the diurnal tidal cycle, the dynamics of POM were affected by sources of organic matter, tidal energy, and seasonal factors. The contribution of mangrove detritus to POM reached a maximum at the low tide and was enhanced during the rainy season, whereas marine phytoplankton contribution was highest at high tide.  相似文献   

Estimation of Pore Water Pressure of Soil Using Genetic Programming     

Ankit Garg  Akhil Garg  K. Tai  S. Sreedeep 《Geotechnical and Geological Engineering》2014,32(4):765-772

Soil–water characteristic curve (SWCC) is one of the input components required for conducting the transient seepage analysis in unsaturated soil for estimating pore water pressure (PWP). SWCC is usually defined by saturated volumetric water content (θ_s), residual water content (RWC) and air entry value (AEV). Mathematical model of PWP could be useful to unearth the important SWCC components and the physics behind it. Based on authors’ knowledge, rarely any mathematical models describing the relationship between PWP and SWCC components are found. In the present work, an evolutionary approach, namely, multi-gene genetic programming (MGGP) has been applied to formulate the relationship between the PWP profile along soil depth and input variables for SWCC (θ_s, RWC and AEV) for a given duration of ponding. The PWP predicted using the MGGP model has been compared with those generated using finite element simulations. The results indicate that the MGGP model is able to extrapolate the PWP satisfactory along the soil depth for a given set of boundary conditions. Based on the given AEV and saturated water content, the PWP along the depth can be determined from the newly developed MGGP model, which will be useful for design and analysis of slopes and landfill covers.  相似文献   

Iron ions increase the thermostability of phycocyanin ofSpirulina maxima     

Jian-hong  Li  Zi-hou  Tai  Tseng  Chao-Tsi 《中国海洋湖沼学报》1998,16(1):127-132

A spectral method to investigate the effect of Fe³⁺, Fe²⁺ on the thermostability of phycocyanin (PC) ofSpirulina maxima showed that iron ions provent decrease of visible light absorbance and fluorescence intensity of PC. Increase in denaturation temperature caused by Fe³⁺ was observed by the micro-differential scanning calorimetric method. All results showed iron ions maintain the aggregation stability of the PC. The absorption spectrum of phycocyanobilin (PCB, a prosthetic group of PC) with Fe³⁺ in chloroform was quite different from that of free PCB.

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刚果(金)DIMMA铜钴矿床地质特征及成因分析   总被引：1，自引：0，他引：1       下载免费PDF全文

刘运纪  王纪昆  张泰 《地质找矿论丛》2011,26(4):446-452

DIMMA铜钴矿区位于著名的刚果（金）-赞比亚卢菲利褶皱弧铜钴矿带的北西端。DIMMA铜钻矿床的形成与成岩期的火山活动、同生断裂活动有关,并受后期造山过程中的褶皱、断裂和变质作用的改造和次生富集,形成多成因多重控制的铜钴矿床。  相似文献   

Satellite altimeter observations of nonlinear Rossby eddy–Kuroshio interaction at the Luzon Strait     

Quanan Zheng  Chang-Kuo Tai  Jianyu Hu  Hongyang Lin  Rong-Hua Zhang  Feng-Chun Su  Xiaofeng Yang 《Journal of Oceanography》2011,67(4):365-376

Satellite altimeter sea level data from 1993 to 2008 are used to analyze the interaction of nonlinear Rossby eddies with the Kuroshio at the Luzon Strait (LS). The sea level anomaly data show that the west Pacific (WP) is a source of nonlinear Rossby eddies, and the South China Sea (SCS) is a sink. The LS serves as a gateway between the two. The scale analysis indicates that eddies with a radius larger than 150 km are strong enough to significantly alter the Kuroshio and are able to modify the local circulation pattern. Statistical analysis indicates that the probability for eddies to penetrate through the Kuroshio may reach at least 60%. A case study of an anticyclonic mesoscale eddy passing through the LS in June–July 2004 indicates that the Kuroshio behaves as an unsteady flow with its stream path frequently modified, in a way of cutting off, meandering and branching during its interaction with the eddy. We therefore suggest that nonlinear Rossby eddies may play a significant role in modification of the local circulation system near the LS and in exchanges of the mass, momentum and energy between the WP and the SCS.  相似文献   

地球模型对季节性负荷形变计算的影响——以川滇地区为例     

佘雅文  吴伟伟  刘泰  付广裕 《地震》2021,41(4):46-56

利用川滇地区的GNSS和GRACE数据, 结合不同地球模型和负荷理论, 研究了地球模型对地表季节性负荷形变计算的影响, 该工作对于选取合适的地球模型开展负荷形变研究具有一定的参考价值。 研究表明: ① 川滇地区GNSS观测的地壳垂向季节性形变振幅为20 mm左右, GRACE反演的垂向形变与GNSS的结果相位一致, 振幅存在差异。 ② 区域地球模型的负荷勒夫数与其他地球模型的差异较大, 且负荷勒夫数h_n对地球结构的变化较为敏感。 ③ 区域地球模型可以改善GRACE反演的负荷形变结果, 从而减小与GNSS观测结果的差异。 ④ 川滇地区大部分GNSS测站的加权均方根比值减小量呈现由东北向西南方向逐渐增加的变化趋势。  相似文献