Atmospheric dust contribution to deep-sea particle fluxes in the subtropical Northeast Atlantic     

Juliane Brust  Joanna J. Waniek 《Deep Sea Research Part I: Oceanographic Research Papers》2010,57(8):988-998

The lithogenic flux of sediment trap material was analyzed from a three year time series (February 2002–March 2005) at 2000 m depth in the Northeast Atlantic (Kiel 276, 33°N, 22°W) with regards to the seasonal and interannual variability of flux intensity and mineralogy—by applying an automated particle SEM-EDX analysis (scanning electron microscope-energy dispersive X-ray analysis). The lithogenic flux shows strong interannual variations with highest lithogenic flux rates occurring during January–February and April–March coupled to the total particle flux. Mean lithogenic flux rates for the sample years are 7.1 (2002–2003), 5.1 (2003–2004) and 16.1 mg m^?2 d^?1 (2004–2005). Mineral assemblages from the three sample years reveal distinct major minerals related to specific source regions. Clay minerals dominate the lithogenic fraction within the years 2002 and 2004 with illite (2002–2003) and palygorskite (2003–2004) being the major clay minerals. During the year 2004–2005, quartz is the major lithogenic mineral accompanied by smectite. The mineral assemblages hint to a mixture of North African source areas with dominant sources in Mauritania and north western parts of NW Africa for the years 2002–2004 and central Sahara (Algeria–Mali) within the year 2004–2005.  相似文献   

Reconstructing climate variability on the northeastern Tibetan Plateau since the last Lateglacial – a multi-proxy,dual-site approach comparing terrestrial and aquatic signals     

Juliane Wischnewski  Steffen Mischke  Yongbo Wang  Ulrike Herzschuh 《Quaternary Science Reviews》2011,30(1-2):82-97

A sediment core from a closed basin lake (Lake Kuhai) from the semi-arid northeastern Tibetan Plateau was analysed for its pollen record to infer Lateglacial and post glacial vegetation and climatic change. At Lake Kuhai five major vegetation and climate shifts could be identified: (1) a change from cold and dry to relatively warmer and more moist conditions at 14.8 cal ka BP; (2) a shift to conditions of higher effective moisture and a stepwise warmer climate at 13.6 cal ka BP; (3) a further shift with increased moisture but colder conditions at 7.0 cal ka BP; (4) a return to a significantly colder and drier phase at 6.3 cal ka BP; (5) and a change back to relatively moist conditions at 2.2 cal ka BP. To investigate the response of lake ecosystems to climatic changes, statistical comparisons were made between the Lake Kuhai pollen record and a formerly published ostracod and sedimentary record from the same sediment core. Furthermore, the pollen and lacustrine proxies from Lake Kuhai were compared to a previously published pollen and lacustrine record from the nearby Lake Koucha. Statistical comparisons were done using non-metric multidimensional scaling and Procrustes rotation. Differences between lacustrine and pollen responses within one site could be identified, suggesting that lacustrine proxies are partly influenced by in-lake or local catchment processes, whereas the terrestrial (pollen) proxy shows a regional climate signal. Furthermore, we found regional differences in proxy response between Lake Kuhai and Lake Koucha. Both pollen records reacted in similar ways to major environmental changes, with minor differences in the timing and magnitude of these changes. The lacustrine records were very similar in their timing and magnitude of response to environmental changes; however, the nature of change was at times very distinct. To place the current study in the context of Holocene moisture evolution across the Tibetan Plateau, we applied a five-scale moisture index and average link clustering to all available continuous palaeo-climate records from the Tibetan Plateau to possibly find general patterns of moisture evolution on the Plateau. However, no common regional pattern of moisture evolution during the Holocene could be detected. We assign this to complex responses of different proxies to environmental and atmospheric changes in an already very heterogeneous mountain landscape where minor differences in elevation can cause strong variation in microenvironments.  相似文献   

Seismic Sequence in Carbonate Rocks By Vibrational Liquefaction   总被引：16，自引：0，他引：16  

Qiao Xiufu  Song Tianrui  Gao Linzhi  Peng Yang  Li Haibing  Gao Mai  Song Biao  Zhang QiaodaInstitute of Geology  Chinese Academy of Geological Sciences  Beijing 《《地质学报》英文版》1994,68(3)

On the basis of the records of strong seismic events taking place in soft carbonate sediments, a new seismic sequence system of vibrational liquefaction is established, which consists of a series of units, such as escaped structure of micrite veins and liquefied deformation formed in the period of seismic liquefaction, land subsidence structure after liquefaction, tsunamic hummocky and turbidite produced by seismic events, This sequence is a generalization and summation of field observation in vast areas, which shows the whole process of a strong seismic event and provides an unified theoretical explanation. The pattern of the seismic sequence by vibrational liquefaction provides one of correlation standards for geologists in the field to discriminate events in carbonate sequences. Based on the pattern of seismic sequence, the authors first advance a new conception of the Palaeo-Tanlu (Tancheng-Lujiang) Zone and discuss primarily its geological significations.  相似文献   

东北三江平原几个钻孔剖面的孢粉组合分析及其意义   总被引：7，自引：0，他引：7       下载免费PDF全文

叶永英  严富华  麦学舜 《地质科学》1983,(3):259-266

三江平原位于我国东北的边陲,系黑龙江、松花江、乌苏里江汇流而成的冲积平原。其位置在东经129°11′20″至135°5′10″,北纬43°49′55′至48°27′40″(图1)。  相似文献   

Cloning and Characterization of an Abalone （Haliotis discus hannai ） Actin Gene   总被引：2，自引：0，他引：2  

MAHongming XUWei MAIKangsen LIUFUZhiguo CHENHong 《中国海洋大学学报(英文版)》2004,3(2):145-149

1　Introduction　Actinisanimportantcontractileproteinineukary oticcells .Itisoneofthetwomajorcomponentsin volvedinthecontractionofmusclecells .Innon mus clecells ,itisthemajorpartofcytoskeletoninvolvedinmanyprocessessuchascellmotility ,endocytosis ,exocyt…  相似文献   

黄河流域近40年日照百分率的气候变化特征   总被引：34，自引：1，他引：34  

买苗  曾燕  邱新法  高苹  王萧宇 《气象》2006,32(5):62-66

利用黄河流域及其周边146个气象站1960--2000年逐月日照百分率资料，研究分析了黄河流域日照百分率的气候变化趋势。结果表明，就整个流域平均而言，日照百分率呈明显下降趋势，黄河流域年平均日照百分率在20世纪90年代较60年代下降了2．49％；日照百分率的下降主要表现在夏季和冬季，春季和秋季下降不明显。对日照百分率气候变化的空间分析表明，除极少数台站的日照百分率呈略有上升趋势外（主要出现在流域上游），黄河流域日照百分率的下降表现得非常明显，遍布整个流域的中、下游。  相似文献   

肇庆市一次超级单体的多普勒雷达资料分析   总被引：5，自引：1，他引：5  

郭媚媚  麦冠华  胡胜  何华庆 《气象》2006,32(6):97-101

利用广州S波段多普勒雷达资料,对2004年7月1日夜间发生在广东省肇庆市的一次强对流天气过程进行分析,发现引起这次强对流的风暴具有超级单体风暴的特征。这个超级单体南边出现两条明显的出流边界,分别位于钩状回波的西南和东南。相应的中低层径向速度图呈现一个弱中尺度气旋,旋转速度达12m·s-1。该超级单体的移动方向在盛行风向的右侧约30°,属于右移风暴。  相似文献   

新疆14C年代测定及数据集（I＊）     

阮成雯  高峰林 《内陆地震》1998,12(1):83-91

主要介绍新疆维吾尔自治区地震局放射性同位素碳测年实验室的１４Ｃ测年原理,样品的前处理、样品的化学制备,低水平放射性测量方法及测定年代。首次公布一批１４Ｃ年代测定数据。  相似文献   

Sm-Nd dating of Seve eclogites,Norrbotten, Sweden — Evidence for early Caledonian (505 Ma) subduction     

Mai Britt E. Mørk  Kåre Kullerud  Arne Stabel 《Contributions to Mineralogy and Petrology》1988,99(3):344-351

The Seve Nappes consist of long-transported thrust sheets belonging to the Upper Allochthon within the Scandinavian Caledonides. Eclogites from two different megalenses within the Seve Nappe Complex in Norrbotten (northern Sweden) have been dated with the Sm-Nd method. The two eclogite-bearing megalenses have been subjected to different pressure and temperature conditions during the high-pressure metamorphism. Garnet + omphacite + whole-rock from TS2 within the Tsäkkok Lens give an age of 505±18 Ma (2), I=0.512231±0.000024, MSWD=0.10. Garnet and whole-rock from TS5 and whole-rock TS3 also fall on the above isochron. The composite isochron gives an age of 503±18 Ma (2). These results are interpreted to date the peak of the high-pressure metamorphism (500–630° C and 12–15 kbars) for the Tsäkkok Lens. The eclogites in the Vaimok Lens (at Grapesvarre) were subjected to higher pressure and temperature conditions and more extensive reequilibration during the early cooling stages. Retrograde breakdown-reactions accompanied by retrograde zoning of relict garnet seems to be associated with disturbance of the Sm-Nd isotopic systems. In contrast, a sample with unzoned garnet and well preserved high-pressure mineralogy from Grapesvarre gives a Sm-Nd garnet + omphacite age of 503±14 Ma (2), I = 0.512010±0.000038 (2). The ages for the Seve eclogites are significantly older than the Sm-Nd eclogite dates from the Western Gneiss Region of Norway (WGR), suggesting the existence of at least two eclogite-forming events in the Caledonide Orogen. The younger event has been related to the main continent-continent collision stage of the Caledonian Orogeny, while the older event that led to the production of the Norrbotten eclogites must have taken place several hundred kilometres to the north and in a different tectonic setting more oceanward to the WGR. It appears that the older event (ca. 505 Ma) was restricted to the subduction of dyke-intruded sedimentary cover rocks which are thought to represent the rifted edge of the Baltic continent.  相似文献   

一种准确而快速的运动目标检测算法   总被引：2，自引：0，他引：2  

曾脉  左志宏  常晓夫  何煊 《成都信息工程学院学报》2008,23(4)

运动目标的检测是计算机视觉和图像编码研究的主要内容,有着广泛的应用领域.减背景法是常用的方法之一,但其受环境光照影响;而帧差法又不能完全提取出目标的所有相关点.针对传统运动目标检测算法的不足,提出基于动态阈值的减背景法与帧差法相结合的运动目标检测算法.实验证明,算法既能完全提取出目标的所有相关点,又适应复杂变化的环境,运动目标检测的精确度和速度都有了明显的提高.  相似文献