西藏仲巴白垩纪-古近纪孢粉组合及其意义   总被引：3，自引：1，他引：2  

李建国  张一勇  蔡华伟  郭震宇  万晓樵 《地质学报》2008,82(5):584-595

西藏的白垩—古近纪孢粉资料迄今鲜有发掘,因此我们对西藏当时的古植物区系、古植被和陆地生态系统等的了解也就甚为了了。本文对位处当时劳亚大陆南部边缘的仲巴县错江顶白垩系—古近系进行了孢粉分析。研究揭示,剖面的孢粉组合可划分为两个孢粉组合带,自下而上分别为Classopollis-Exesipollenites-Cycadopites组合和Pinuspollenites-Quercoidites-Trilobapollis组合,其时代分别为晚白垩世晚期Santonian—Maastrichtian和古近纪古新世—始新世。剖面的白垩系/古近系界线可能位于曲贝亚组和曲下组之间。针叶树花粉大量繁盛,特别是一些类型如Abiespollenites、Cedripites、Piceapollis和Tsugaepollenites仅见于曲下组顶部至加拉孜组底部的孢粉组合,反映了一次与构造运动密切相关的古环境变化事件,可能指示了印度—劳亚板块碰撞的开始。研究区孢粉植物区系与中国南方植物区系有很好的可比性,而与印度北缘同期植物区系区别明显,暗示着印度与劳亚大陆之间的海域直至始新世仍然具有明显的隔离作用,阻碍着两侧大陆上植物区系间的交流。  相似文献   

Mercury pollution from artisanal mercury mining in Tongren, Guizhou, China     

Ping Li  Xinbin Feng  Lihai Shang  Guangle Qiu  Bo Meng  Peng Liang  Hua Zhang   《Applied Geochemistry》2008,23(8):2055-2064

Concentrations of total Hg (T-Hg) were measured in mine waste, stream water, soil and moss samples collected from the Tongren area, Guizhou, China to identify potential Hg contamination to local environments, which has resulted from artisanal Hg mining. Mine waste contained high T-Hg concentrations, ranging from 1.8 to 900 mg/kg. High concentrations of Hg were also found in the leachates of mine waste, confirming that mine waste contains significant water-soluble Hg compounds. Total Hg distribution patterns in soil profiles showed that top soil is contaminated with Hg, which has been derived from atmospheric deposition. Data suggest that organic matter plays an important role in the binding and transport of Hg in soil. Elevated T-Hg concentrations (5.9–44 mg/kg) in moss samples suggest that atmospheric deposition is the dominant source of Hg to local terrestrial ecosystems. Concentrations of T-Hg were highly elevated in stream water samples, varying from 92 to 2300 ng/L. Particulate Hg in water constituted a large proportion of the T-Hg and played a major role in Hg transport. Methyl–Hg (Me–Hg) concentrations in the water samples was as high as 7.9 ng/L. Data indicate that Hg contamination is dominantly from artisanal Hg mining in the study area, but the extent of Hg contamination is dependent on the mining history and the scale of artisanal Hg mining.  相似文献   

Assessing vegetation dynamics impacted by climate change in the southwestern karst region of China with AVHRR NDVI and AVHRR NPP time-series   总被引：6，自引：0，他引：6  

J. Wang  J. J. Meng  Y. L. Cai 《Environmental Geology》2008,54(6):1185-1195

The relationship between climate change and vegetation dynamics in the southwestern karst region of China has been identified by recent studies. Based on previous researches and AVHRR (Advanced Very High Resolution Radiometer) GIMMS (Global Inventory Monitoring and Modeling Studies) NDVI (Normalized Difference Vegetation Index) (1982–2003) and AVHRR GloPEM (Global Production Efficiency Model) NPP (Net Primary Production) (1981–2000) datasets, vegetation dynamics impacted by climate change in the southwestern karst region of China were assessed. The results show that: (1) since the early 1980s, both vegetation cover density and net primary production have insignificant ascending tendencies. However, the inter-annual variation rates of vegetation indexes have apparent spatial differentiations; (2) the correlation coefficients between the inter-annual variations of vegetation indexes and the inter-annual variations of climate factors vary geographically; (3) as indicated by NDVI and NPP, various vegetation types have different responses to climate change, and the annual mean temperature variation has more significant impact on vegetation dynamics than the annual precipitation variation in the study area; (4) distribution laws of correlation coefficients between the inter-annual variations of vegetation indexes and the inter-annual variations of climate factors in different climate conditions are apparent. All these findings will enrich our knowledge of the natural forces which impact the stability of the karst ecosystems and provide scientific basis for the management of the karst ecosystems.  相似文献   

黑龙江北部孙吴——嘉荫盆地沉积相类型及其演化   总被引：4，自引：1，他引：3       下载免费PDF全文

杨建国  邵曌一  吴河勇  刘俊来 《地质科学》2008,43(4):648-660

通过对孙吴-嘉荫盆地淘淇河组、永安村组、太平林场组、鱼亮子组、乌云组和孙吴组露头剖面详细的沉积学研究,查明该盆地从淘淇河组到孙吴组发育的沉积相类型有冲积扇、辫状河、曲流河、扇三角洲、辫状河三角洲、曲流河三角洲、湖底扇和湖泊。冲积扇及扇三角洲主要发育于淘淇河组和孙吴组;辫状河及辫状河三角洲主要发育于鱼亮子组和乌云组;曲流河及曲流河三角洲主要发育于永安村组和太平林场组,各组均有湖泊相沉积发育。孙吴-嘉荫盆地从淘淇河组到乌云组,具有冲积扇-扇三角洲-湖泊→曲流河-曲流河三角洲-湖泊→辫状河-辫状河三角洲-湖泊→冲积扇-扇三角洲-湖泊的沉积演化规律,反映晚白垩-古新世构造活动性减弱,中-上新世孙吴组沉积时重又趋于活动。  相似文献   

BDS网络RTK参考站三频整周模糊度解算方法   总被引：1，自引：1，他引：0  

高猛  徐爱功  祝会忠  葛茂荣  杨秋实 《测绘学报》2017,46(4):442-452

北斗卫星导航系统是目前唯一一个全星座提供三频观测数据的卫星导航定位系统,三频观测值有助于载波相位整周模糊度的快速、准确固定。本文提出了一种BDS网络RTK参考站三频整周模糊度解算方法。首先利用B2、B3频率的观测值及严格的模糊度固定标准确定超宽巷整周模糊度,将固定的超宽巷整周模糊度与其他宽巷整周模糊度的线性关系作为约束条件,然后估计宽巷整周模糊度、相对天顶对流层延迟误差和电离层延迟误差,并搜索确定宽巷整周模糊度。利用固定的宽巷整周模糊度与三频载波相位整周模糊度的整数线性关系,将线性关系加入载波相位整周模糊度参数估计观测模型中,然后确定载波相位整周模糊度。使用实测的CORS网BDS三频观测数据进行算法验证,结果表明,该方法可正确有效地实现参考站间三频载波相位整周模糊度的快速解算。  相似文献   

一种GPS多路径反射信号的雪深反演     

税广通  郑南山  周方平  严薛峰  史永鹏  班盟  祁作栋 《测绘科学》2017,42(10)

针对传统雪深测量缺乏必要时空敏感性的不足,该文在分析GPS信号多路径反射模型的基础上,利用GPS信噪比观测数据,通过分离提取多路径反射分量研究其时频特性,探讨GPS多路径信号与雪深及其变化关系并进行反演建模。依据菲涅尔反射区理论,确定了反射区域范围,进一步探讨卫星、波段选择及初始反射高度确定等。对比实验研究表明,反演结果与实测值吻合较好,相关系数为0.93,均方根误差为8.6cm;信噪比多路径反射分量的频率能有效跟踪积雪深度的变化。  相似文献   

Simulating the role of gravel in freeze–thaw process on the Qinghai–Tibet Plateau     

Pan  Yongjie  Lyu  Shihua  Li  Suosuo  Gao  Yanhong  Meng  Xianhong  Ao  Yinhuan  Wang  Shujin 《Theoretical and Applied Climatology》2017,127(3-4):1011-1022

Soils containing gravel (particle size ≥2 mm) are widely distributed over the Qinghai–Tibet Plateau (QTP). Soil mixed with gravel has different thermal and hydrological properties compared with fine soil (particle size <2 mm) and thus has marked impacts on soil water and heat transfer. However, the most commonly used land models do not consider the effects of gravel. This paper reports the development of a new scheme that simulates the thermal and hydrological processes in soil containing gravel and its application in the QTP. The new scheme was implemented in version 4 of the Community Land Model, and experiments were conducted for two typical sites in the QTP. The results showed that (1) soil with gravel tends to reduce the water holding capacity and enhance the hydraulic conductivity and drainage; (2) the thermal conductivity increases with soil gravel content, and the response of the temperature of soil mixed with gravel to air temperature change is rapid; (3) the new scheme performs well in simulating the soil temperature and moisture—the mean biases of soil moisture between the simulation and observation reduced by 25–48 %, and the mean biases of soil temperature reduced by 9–25 %. Therefore, this scheme can successfully simulate the thermal and hydrological processes in soil with different levels of gravel content and is potentially applicable in land surface models.

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基于非期望产出的城市发展效率时空差异探讨——以中国东部沿海地区城市为例   总被引：1，自引：1，他引：0  

狄乾斌  孟雪 《地理科学》2017,37(6):807-816

基于非期望产出视角,采用SBM模型测度2005~2014年中国东部沿海地区53个城市（不包括港、澳、台、三沙市）的城市发展效率,并分析其时空差异特征及其影响因素。结果表明：① 考虑非期望产出的城市发展效率值低于不考虑非期望产出的城市发展效率值,并且更符合城市实际发展; ② 中国东部沿海地区城市发展效率整体水平不高,波动幅度大,阶段特征明显,整体呈先上升后下降的趋势;③ 在时空分析特征中,城市发展效率的区域差异明显,近2 a有缩小的趋势;整体城市发展效率空间呈现“北部围绕青岛市,中部围绕上海市,南部围绕深圳市”的发展格局;④ 在影响因素分析中,经济规模对城市发展效率产生正向影响,第二产业结构水平和污染处理能力对城市发展效率产生负向影响,传统的加工制造业、高耗能重污染工业和污染处理不到位是导致城市发展效率降低的主要原因。  相似文献   

GPS及AVHRR资料在浅海潮间带测量中的应用   总被引：1，自引：0，他引：1       下载免费PDF全文

范德新  杨亚新  尹成华  汤建国 《气象》2001,27(3):19-22

通过利用GPS及渔探器实测，并进行潮位订正，获得南通浅海海域大量测点的高程资料，通过对多时相各通道NOAA卫星照片进行筛选，挑选能反映浅海地貌的通道资料，从中读取各测点相对应的灰度值，在此基础上利用分级线性回归，建立不同高程范围内的高程，灰度线性回归方程，确定不同高程的灰度阈值，从而测量出南通市浅海海域不同高程以上的潮间带面积，分布。  相似文献   

岩石圈塑性流动波的实验研究(Ⅰ)   总被引：2，自引：4，他引：2       下载免费PDF全文

王绳祖  李建国  张宗淳 《地震地质》2001,23(3):407-418

实验采用了适当配比的塑化松香 ,模拟岩石圈延性层 ,研究边界驱动条件下塑性流动波的传播过程。实验表明 ,塑性流动波类似于粘性重力波 ,并有“快波”和“慢波”之分 ,二者分别由主波和辅波叠加而成。主波类似于孤立波或涌波。根据相似原理 ,“快波”主波的外推波速约为 0 .12～2 .5km/a ,在波速量级上大致相当或接近于岩石圈下层某些控制地震迁移的塑性流动波  相似文献