A high-resolution Holocene diatom record on the North Icelandic shelf   总被引：1，自引：0，他引：1  

LIHUA RAN  HUI JIANG  KAREN LUISE KNUDSEN  JÓN EIRÍKSSON 《Boreas: An International Journal of Quaternary Research》2008,37(3):399-413

A high-resolution diatom record from core MD99-2275 reveals a series of palaeoceanographic changes on the North Icelandic shelf since about 9000 cal. yr BP. The influence of relatively warm high-salinity Atlantic water-masses of the IC was strong in the study area during the Holocene Climate Optimum (8760 (base of record) to c . 5300 cal. yr BP) and peaked between c . 8000 and 7000 cal. yr BP. There is a general cooling trend from c . 7000 cal. yr BP to the present, which is indicated by an increase in the influence of cold Polar water-masses from the EGC and the EIC and a decrease in the influence of the IC. A major change in diatom assemblages at around 5300 cal. yr BP indicates a palaeoceanographic shift on the North Icelandic shelf in the mid-Holocene. In addition, several abrupt palaeoceanographic changes are distinguished. Enhanced influence of Polar waters is reflected during the intervals 8120–8000, 6650–6100, 4300–4100, 3000–2700, 1300–1100 and 600–200 cal. yr BP. The palaeoceanographic indication of the diatom record of core MD99-2275 is consistent with the indication of other environmental parameters from the same core, such as benthic and planktonic foraminifera as well as magnetic properties, and the results are also consistent with palaeoclimatic records from adjacent areas around Iceland and in the North Atlantic region.  相似文献   

三维GIS平台复杂工况下的电气校验     

蒋剑  惠帅  李毓  徐华秒  鲁思光 《测绘科学》2017,42(1)

针对传统输电线路设计过程中校验过程困难、精度低的问题,基于三维GIS平台设计了三维电气校验模块,利用悬链线理论、空间坐标转换、状态方程等计算方法实现了不同的工况条件下对"导线对地距离""导地线间距离""导线对地物距离""极限档距"及"安全间隙"的校验,校验算法的准确性通过了设计院的校核。通过多个工程的试用表明,该方法不仅提高设计人员的工作效率,而且可以提高电气校验的精度,研究结果对输电线路数字化设计过程中电气校验具有一定的参考价值。  相似文献   

EISCAT雷达观测到的极区电离层等离子体反常对流          下载免费PDF全文

马淑英  刘鹏  刘会欣  徐继生  K Schlegel 《地球物理学报》2001,44(4):446-453,T001

综合分析EISCAT雷达与卫星当地测量数据,并利用磁层磁场模式对磁力线进行追踪,研究了发生在极光椭圆朝极盖边界附近电离层中,一例反常的背离太阳流动的强等离子体对流事件,及相关的太阳风-磁层-电离层耦合过程.结果表明,磁暴期间IMFBz指向南时观测到这一反常高速对流,及其相应的等离子体性态特征,很可能是向阳侧磁层顶磁重联过程在电离层中的印记.  相似文献   

用接收函数方法研究中国及邻区上地幔间断面的埋藏深度   总被引：10，自引：4，他引：10       下载免费PDF全文

杨毅  周蕙兰 《地球物理学报》2001,44(6):783-792

使用中国及邻区的18个数字化地震台的宽频带三分向远震记录图,筛选计算得到了263条径向接收函数,并拾取了在41Okm和660km间断面上的透射转换震相P4S、P660S与P波的到时差.通过调整各台站之下的速度模型中这两个间断面的深度,使理论接收函数的P4S、P660S与P波的到时差与观测值相符,最终确定这两个间断面的实际埋藏深度.结果表明,各台站之下4km间断面的平均深度为403km,具有明显的横向不均匀性和区域性,其中北京台、西安台、兰州台和恩施台等的埋藏深度较浅,琼中台、CHTO等台较深.660km间断面的平均埋藏深度为663km,也存在明显的横向不均匀性,其中牡丹江台和MAJO台的较深,琼中台和HYB台的较浅.  相似文献   

二元模式下水资源承载力系统动态仿真模型研究   总被引：77，自引：4，他引：77  

惠泱河  蒋晓辉  黄强  薛小杰 《地理研究》2001,20(2):191-198

首先探讨了二元模式下水资源承载力的内涵,然后根据水资源承载力的特点探讨了运用系统动力学方法研究水资源承载力的可行性,并在此基础上建立了二元模式下水资源承载力系统动力学动态仿真模型,最后以典型缺水地区陕西关中为例,根据未来水资源的变化趋势,研究了不同方案下关中水资源承载力,得到提高关中水资源承载力的满意方案。  相似文献   

藏东地区新生代构造体系与成矿的关系   总被引：7，自引：0，他引：7       下载免费PDF全文

谭富文  王高明  惠兰  汪名杰  李忠雄  王小龙 《地球学报》2001,22(2):123-128

区域构造和微构造分析表明，新生代藏东地区构造应力场自印支燕山期的NE-SW向挤压向喜马拉雅山期的NNE-SSW向压扭性转变，表现在：（1）沿昌都地块两侧及古生代一中生代形成的深大断裂带发生了大规模的右旋走滑活动，伴重型较强的碎裂岩化、拉伸线埂和剑鞘褶皱等，沿主断裂两侧叠加一系列NW、NNW及NE向雁行式排列的褶皱和张扭性断裂；（2）在区域上，沿大规模右旋走滑断裂两侧形成一系列雁行式排列的第三系走滑拉分盆地；（3）新生代岩浆活动沿走滑断裂两侧的张扭性次级断裂有规律分布，新生代构造体制的转变造成大规模成矿流体与富集，使新生代成为本区最重要的成矿时期，而北澜沧江，妥坝、温泉断裂带及车所乡断裂带北段是该期矿产最有利的富集部位。  相似文献   

Dynamic sea-level change during the last deglaciation of northern Iceland     

MATS RUNDGREN  ÓLAFUR INGÓLFSSON  SVANTE BJÖRCK  HUI JIANG  HAFLIDI HAFLIDASON 《Boreas: An International Journal of Quaternary Research》1997,26(3):201-215

Rundgren, M., Ingólfsson, Ó., Björck, S., Jiang, H. & Haflioason, H. 1997 (September): Dynamic sea-level change during the last deglaciation of northern Iceland. Boreas , Vol. 26, pp. 201–215. Oslo. ISSN 0300–9483.
A detailed reconstruction of deglacial relative sea-level changes at the northern coast of Iceland, based on the litho- and biostratigraphy of lake basins, indicates an overall fall in relative sea level of about 45 m between 11300 and 9100 BP, corresponding to an isostatic rebound of 77 m. The overall regression was interrupted by two minor transgressions during the late Younger Dryas and in early Preboreal, and these were probably caused by a combination of expansions of local ice caps and readvances of the Icelandic inland ice-sheet margin. Maximum absolute uplift rates are recorded during the regressional phase between the two transgressions (10000–9850 BP), with a mean value of c . 15 cm ¹⁴C yr^-1 or 11–12 cm cal. yr^-1. Mean absolute uplift during the regressional phase following the second transgression (9700–9100 BP) was around 6 cm ¹⁴C yr^-1, corresponding to c . 3 cm cal. yr^-1, and relative sea level dropped below present-day sea level at 9000 BP.  相似文献   

油气放射性勘查中若干问题的讨论     

吴慧山  林玉飞 《铀矿地质》1992,8(1):35-42

  相似文献   

EXPERIMENTAL STUDY ON SALTATION OF SOLID GRAINS IN FLOWING WATER     

HU Chunhong  HUI Yujia  and XIA Zhenhuan 《国际泥沙研究》1992,(2)

This paper deals with the saltation of bed-load solid grains in flowing water. Experiments have been carried out by means of high-speed photographing and advanced data processing techniques while the analysis is made by combined method of mechani- cal and statistical theories. Experiments reveal that saltation is the main form of the bed-load transport under ordinary flow conditions. Taking successive saltation as the model of bed-load transport, systematic analysis has been made with regard to the forces acting on grains and the variation of their magnitudes along the saltation trajec- tories to obtain the kinematic and dynamic properties of these grains. The statistical analysis shows that the probability density functions of the relative height and length of saltation are in conformity with distribution, while the probability density functions of the relative velocities of saltation are in conformity with the Gaussian distribution.  相似文献   

皖南中生代中酸性侵入岩中黑云母的类型和构造意义     

邢凤鸣  徐祥 《矿物岩石》1991,(1)

皖南中生代中酸性侵入岩中普遍含有黑云母,按其成分可分为:镁质黑云母、铁质黑云母和黑鳞云母3类,其MF值和∫O_2依次为0.56—0.60,0.42—0.46,0.06—0.13和10~(-12),10~(-14),10~(-18)左右。其寄主岩石的成因类型分别为扬子式同熔型、江南式同熔型和改造型。它们分别占据不同的地区,是不同大地构造单元上的产物。黑云母成分的变化是大地构造环境差异的标志。  相似文献