湖南寒武系第三统混积岩沉积特征与成因探讨     

梁薇  牟传龙  周恳恳  王瑞华  葛祥英  徐鹏辉  郑斌嵩  谭志远 《地质论评》2016,62(4):881-896

湖南地区寒武系第三统发育大量的混积岩及混积层系,其沉积特征、成因及时空分布,对研究寒武纪中上扬子地区东南缘的沉积环境及碳酸盐台地的形成演化具有重要的意义。本文采用野外观察、微观岩石学分析方法对混积岩时空分布、沉积特征、矿物组分进行了研究,首次系统总结了湖南地区寒武系第三统发育的混积层系类型与组合方式,及其分布的6类不同的岩相分区,并按照成分分类依据划分出4种混积岩类型。研究表明,混积岩分布在湘西北地区及湘中地区,靖州—涟源—隆回—宁乡一线以北的区域。混积层系的沉积特征表明,其形成于受周期性强风浪、风暴作用影响的浅水混积陆棚环境或风暴浪基面以下的深水混积陆棚环境,主要成因为机械成因的相缘渐变沉积混合及事件突变沉积混合。混积陆棚的存在,表明寒武纪第三世时期,中上扬子东南缘湘西北地区不发育台缘相带,未建立起完整的镶边碳酸盐台地模式,而为相对平缓的碳酸盐岩为主的浅海混积陆棚模式,混有碎屑岩沉积物。  相似文献   

Effects of low- to high-angle normal faults on sedimentary architectures in the Eocene Wenchang Formation,Enping Sag,Pearl River Mouth Basin,South China Sea     

Q. H. Liu  Y. Shu  X. M. Zhu  X. H. Yang  M. Tan 《Australian Journal of Earth Sciences》2016,63(7):903-922

The effects of low- to high-angle (>30°) normal faults on sedimentary architectural units in the Eocene Wenchang Formation, Enping Sag, Pearl River Mouth Basin (PRMB), South China Sea were investigated utilising a high-quality 3D seismic data set and restored paleogeomorphology. It has been shown that sequence stratigraphic units and sedimentary architecture are significantly controlled by the low- to high-angle normal faults. The Wenchang Formation, a second-order sequence, can be subdivided into two para-second-sequences (the Lower and Upper Wenchang sequences, E₂W^L and E₂W^U) and seven third-order sequences (from base to top: SQ1～SQ7). The low-angle fault confined sequence architecture of the Wenchang Formation is mainly characterised by lateral stacking with the ratio of the vertical subsidence (V) to horizontal slip (H) being reduced from 1/2 for E₂W^L to 1/6 for E₂W^U. In contrast, the high-angle fault confined sequence is characterised by vertical stacking with the ratio of V/H close to 1 for sequences SQ1 to SQ7. In the 3D seismic area, the features of sediment-dispersal pattern were interpreted based on an integrated analysis of paleogeomorphology, seismic reflection characteristics, stratal thickness distribution and multiple attribute clustering. The results show that the large-scale fan delta, belt-shape lacustrine deposit and bird-foot braided delta systems mainly developed in the low-angle fault confined sequences, whereas small-scale fan delta, rhombus-shaped lacustrine deposit and lobe-shaped braided delta systems inherited tectono-sedimentary architectures in the high-angle fault confined sequences.  相似文献   

Shallowness of tropical low clouds as a predictor of climate models’ response to warming     

Florent Brient  Tapio Schneider  Zhihong Tan  Sandrine Bony  Xin Qu  Alex Hall 《Climate Dynamics》2016,47(1-2):433-449

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高建筑对周围建筑雷击保护距离的模拟   总被引：1，自引：1，他引：0       下载免费PDF全文

谭涌波  陈之禄  张冬冬  师正  郭秀峰 《应用气象学报》2016,27(4):498-505

在已有先导连接参数化方案的基础上,选取近地面层为研究区域,保持方案中其他基本参量不变,通过改变闪电的空间形态,在同一建筑分布的背景下进行多次闪电模拟。研究多个建筑之间的屏蔽作用以及建筑雷击保护距离与建筑相关特征参数之间的关系,结果表明:高建筑对矮建筑具有屏蔽作用,并存在一个临界保护距离,当高、矮建筑高度分别为190 m和165 m,宽度均为20 m时,建筑之间的距离在12 m以内,矮建筑受高建筑完全保护不遭受雷击;建筑之间的距离超过12 m,矮建筑遭雷击次数明显增多。  相似文献   

承德市2015年2月20-21日强降雪成因分析     

杨杰  谭国明  尤国军  冯钰博  刘园园 《沙漠与绿洲气象(新疆气象)》2016,10(4):32-38

利用常规观测资料、卫星云图和NECP (1?? 1?)逐6h再分析资料,对承德市2015年2月20～21日强降雪过程环流形势和物理量场进行了分析。结果表明：在此次强降雪过程中,中、低层的西风槽、切变线和地面上东移加强的蒙古气旋构成了有利天气形势,在这些系统的共同作用下不断有干冷空气侵入承德地区与低层西南暖湿气流交汇,持续的西南暖湿气流对此次强降雪的形成和维持至关重要。相对湿度、水汽通量、垂直速度、涡度及垂直螺旋度的分布和演变很好的反映出了此次强降雪过程中物理量场特点：相对湿度和水汽通量的分布说明强降雪区上空湿度较大且有充足的水汽供应,水汽通量的增大与降雪的增强相一致,水汽通量大值中心与强降雪有很好对应关系。强降雪区上空伴有较强上升运动;降雪区上空均为正涡度时最有利于上升运动和降雪;降雪区上空垂直螺旋度均为正或呈"上负下正"的垂直结构均有利于降雪,低层正垂直螺旋度对强降雪变化有很好的指示意义。  相似文献   

Use of an inside buffer method to extract the extent of urban areas from DMSP/OLS nighttime light data in North China     

Minghong Tan 《地理信息系统科学与遥感》2016,53(4):444-458

Defense Meteorological Satellite Program (DMSP)/Operational Linescan System (OLS) nighttime imagery provides a valuable data source for mapping urban areas. However, the spatial extents of large cities are often overestimated because of the effect of over-glow from nighttime light if a fixed thresholding technique is used. In the work reported here, an inside buffer method was developed to solve this issue. The method is based on the fact that the area overestimated is proportional to the extent of the lit area if a fixed threshold is used to extract urban areas in a region/county. Using this method, the extents of urban areas in North China were extracted and validated by interpretations from Landsat Thematic Mapper images. The results showed that the lit areas had a significant linear relationship with the urban areas for 120 representative cities in North China in 2000, with an R² value of over 0.95. This demonstrates that the inside buffer method can be used to extract urban areas. The validation results showed that the inside buffer model developed in 2000 can be directly used to extract the extent of urban areas using more recent nighttime light imagery. This is of great value for the timely updating of urban area databases in large regions or countries.  相似文献   

Two Methods for Predicting Reliability Index and Critical Probabilistic Slip Surface of Soil Slopes     

Xiao-hui Tan  Xian-en Wang  Xiao-jun Hu  Meng-fen Shen  Na Hu 《Geotechnical and Geological Engineering》2016,34(5):1283-1292

Two methods of reliability analysis of soil slopes are studied, and the representative flow charts of both methods are illustrated. Method 1 can predict the reliability index and the critical probabilistic slip surface directly and it is computational efficient, but it needs the development of new codes for integrating the reliability analysis code and the slope stability code. Method 2 makes the reliability analysis code call the slope stability analysis code directly, and each code can be considered as an intact part. The main result of Method 2 is the reliability index of soil slope. Combined with the proposed method for locating the critical slip surface, Method 2 can also predict the probabilistic slip surface. Although Method 2 needs much more callings of the subprogram of slope stability analysis code, it needs not the developing of new computer program. Thus, Method 2 is easy to use and can be applied to different reliability analysis methods and slope stability analysis methods.  相似文献   

Coal-measure source rock characteristics and burial evolution history in the Shisanjianfang Area,Tuha Basin     

Zhiyuan Wu  Suping Peng  Wenfeng Du 《Arabian Journal of Geosciences》2016,9(5):417

Shisanjianfang Area in the eastern margin of Taibei Sag, Tuha Basin, is an important region for oil and gas exploration. In this study, a large number of source rock geochemical data were used to analyze the geochemical characteristics of coal-measure source rocks in the Shisanjianfang Area, Tuha Basin, from three aspects, i.e., organic matter abundance, organic matter type, and organic maturity. The results show that the Jurassic Xishanyao Formation (J₂x) in the study area has great thickness, continuous distribution, and high source rock maturity, and is the major source rock horizon in the study area. The seismic data are used in combination with 1D and 2D basin simulation technology to study the distribution characteristics of the source rocks in Shisanjianfang Area. The results of the simulation research on the source rock maturity history in the study area indicate the following: (1) The source rocks in the Xishanyao Formation (J₂x) have a hydrocarbon generation threshold depth of 1800 m, threshold temperature of 95 °C, and hydrocarbon generation threshold time of about 162 Ma. (2) The Xishanyao Formation (J₂x) has a current formation temperature of 50~110 °C and Ro of 0.6~1.1 % in the peak oil generation stage. (3) The source rock maturity in the study area is shown as being higher in the west while lower in the east, and higher in the north while lower in the south, and the favorable exploration area mainly lies in the northwest of the study area. The results of this study could have important implications for the oil and gas exploration in the margins of Xiaocaohu Sag, Tuha Basin.  相似文献   

织锦巴非蛤斧足颜色与总类胡萝卜素含量相关分析     

李庆昌  刘坦  陈小明  蔡明夷  刘贤德  曾志南 《海洋科学》2016,40(10):120-125

斧足是织锦巴非蛤重要的食用部位。本研究检测了94个织锦巴非蛤斧足的总类胡萝卜素含量(TCC)和3个颜色指标L*(明暗度)、a*(红绿值)、b*(黄蓝值),发现织锦巴非蛤斧足总类胡萝卜素含量和颜色指标在不同个体之间存在较大差异。相关性分析表明,织锦巴非蛤斧足的总类胡萝卜素含量与颜色指标L*、a*、b*之间相关极显著(P0.01),相关系数分别为:–0.546、0.569、0.449。本研究表明,斧足颜色越深,其类胡萝卜素含量也越高可能是一个普遍规律,这对我们接下来选育高类胡萝卜素含量贝类提供了一种直观的参考指标。  相似文献   

Length of stay in urban areas of circular migrants from the mountainous areas in China     

Ming-hong Tan  Xiu-bin Li  Jian-zhong Yan  Liang-jie Xin  Lai-xiang Sun 《山地科学学报》2016,13(5):947-956

Currently, there is limited literature dealing with the length of stay of circular migrants in urban areas (LSCMU), although many studies have discussed the phenomenon of migration and the determinants of migration. This study attempts to fill that gap using survey data from the mountainous areas of Chongqing, Southwest China. From a comparative perspective, this study divided workers into two groups (a young group aged between 16 and 35 years and an old group aged between 36 and 65 years). The average LSCMU values for the young and old groups were 225 days and 174 days, respectively. Two multi-regression models were used to estimate the determinants of LSCMU in the two groups. The results showed that LSCMU was closely related to individual factors in both groups, including gender, age and job training. Family and community factors, including household size, arable land per capita and the distance from market, had much weaker effects on the dependent variable, especially in the older group. It was noticeable that job training had significant positive effects on LSCMU in both groups; these findings have special implications for the urbanization process in China.  相似文献