西藏南部晚始新世打拉埃达克质花岗岩及其构造动力学意义

打拉二云母花岗岩岩体位于雅拉香波穹隆的东南,侵入到中生代以前的变质岩系(眼球状花岗质片麻岩和石榴黑云母片麻岩)和特提斯沉积岩(页岩和砂岩)中,主要由石英、斜长石、钾长石、黑云母和白云母组成,形成于～44.3Ma。打拉二云母花岗岩地球化学特征表明:打拉花岗岩具有高Al_2O_3(16.0%～17.0%)、Na_2O/K_2O(1.2)以及A/CNK比值(1.05),表明打拉花岗岩为富钠过铝质花岗岩;轻稀土(LREE)富集,重稀土(HREE)相对亏损,HREE中的Ho到Lu元素有变平的特征((Ho/Lu)_N=1.11～1.46);具有微弱或无Eu异常,Eu/Eu~*=0.87～0.95;较高的初始Sr同位素比值(~(87)Sr/~(86)Sr(i)=0.71754～0.71785)和较低的初始Nd比值(ε_(Nd)(i)=-9.15～-12.4)。打拉花岗岩具有高Sr含量(为355×10~(-6)～416×10~(-6))和Sr/Y的比值(59.1～71.5)、高La/Yb比值、低Y及HREE亏损的特征,与埃达克质花岗岩类似。上述特征表明打拉花岗岩是在较高压力条件下,以角闪岩为主的深部岩石部分熔融的结果。     

On the relationship between flow and suspended sediment transport over the crest of a sand dune, Río Paraná, Argentina

The links between large‐scale turbulence and the suspension of sediment over alluvial bedforms have generated considerable interest in the last few decades, with past studies illustrating the origin of such turbulence and its influence on flow resistance, sediment transport and bedform morphology. In this study of turbulence and sediment suspension over large sand dunes in the Río Paraná, Argentina, time series of three‐dimensional velocity, and at‐a‐point suspended sediment concentration and particle‐size, were measured with an acoustic Doppler current profiler and laser in situ scattering transmissometer, respectively. These time series were decomposed using wavelet analysis to investigate the scales of covariation of flow velocity and suspended sediment. The analysis reveals an inverse relationship between streamwise and vertical velocities over the dune crest, where streamwise flow deceleration is linked to the vertical flux of fluid towards the water surface in the form of large turbulent fluid ejections. Regions of high suspended sediment concentration are found to correlate well with such events. The frequencies of these turbulent events have been assessed from wavelet analysis and found to concentrate in two zones that closely match predictions from empirical equations. Such a finding suggests that a combination and interaction of vortex shedding and wake flapping/changing length of the lee‐side separation zone are the principal contributors to the turbulent flow field associated with such large alluvial sand dunes. Wavelet analysis provides insight upon the temporal and spatial evolution of these coherent flow structures, including information on the topology of dune‐related turbulent flow structures. At the flow stage investigated, the turbulent flow events, and their associated high suspended sediment concentrations, are seen to grow with height above the bed until a threshold height (ca 0·45 flow depth) is reached, above which they begin to decay and dissipate.     

2010年度大气科学领域项目评审与研究成果分析

1 2010年项目申请、送审与资助情况2010年地球科学五处共受理各类项目863项,比2009年(768项)增加了95项。面上项目、青年基金和地区基金3类项目共791项。天气与气候     

基于物元理论的滑坡灾害易损性分析及其防灾减灾对策——以湖南湘西为例

物元分析是解决矛盾问题的规律和方法,是系统科学、思维科学和数学的交叉学科。本文简单分析了物元概念的可拓性,通过以湖南湘西为例,应用物元理论知识分析说明危岩、滑坡灾害的社会经济易损性具有发散性、可扩性、相关性和共扼性的特点,提出减灾工作应在传统理论研究的基础上,应用物元理论采用可拓学的方法科学地制定防灾减灾对策,以期为滑坡区域防灾、减灾规划工作提供新的理论和方法依据。     

灌浆钻灌一体化工艺实践与探讨

历来灌浆是由两个不同的工序组合起来的,即成孔与灌浆,成孔由一套钻具完成,灌浆又是由另一套灌浆管系列完成,之间无相联关系。因此,在某些施工区域,可由钻机组与灌浆组分别完成。通过工艺改进后,可将成孔与灌浆改为一个工序,使灌浆质量与效率均能得到提高。介绍了钻灌一体化技术的原理、工艺流程及其工艺特点,并列举了工程实例。     

广西六景泥盆系弗拉斯阶-法门阶界线层牙形石生物地层及碳同位素组成

广西六景泥盆系剖面是中国泥盆系标准剖面之一,通过对其弗拉斯阶-法门阶(F-F)界线附近地层进行详细的牙形石生物地层研究,自下而上识别出3个牙形石带:晚rhenana带、linguiformis带和triangularis带。F-F界线位于融县组下部(第7号层与第8号层之间),在谷闭组顶界之上3.32,m处。碳同位素的分析结果表明,F-F之交δ13C具有显著正偏移,增幅为2.0‰,与湖南老江冲、广西垌村和杨堤以及欧洲、美洲、非洲和澳洲等地的F-F界线附近的碳同位素记录一致,且具有相近的变化幅度。δ13C正异常与F-F界线上的生物灭绝有关,由于食微生物的高等生物灭绝,微生物大量繁盛,诱导海水缺氧,导致海洋有机碳埋藏速率增加,从而形成δ13C的正偏。F-F界线层发育一套以碎屑灰岩为特色的事件沉积,该事件沉积在广西乃至全球具有等时性,可能与小行星碰撞地球引起的全球性海啸有关。     

一个再生台风的分析

8214号台凤,不但路径奇异,而且生命史也奇特。本文利用GMS云图和常规的天气资料对其进行跟踪和分析,在揭示事实的基础上,着重对它的再生过程和在台风减弱阶段,中心从密蔽云区中外移且分离的现象进行探讨,得到一些有意义的结果。     

冬季中东急流与中国气候异常的联系

用NCEP/NCAR再分析资料和中国160站降水和气温资料,研究了冬季中东急流与中国气候异常的联系。结果表明:中东急流偏强、位置偏东南时,200 hPa上孟加拉湾、中南半岛及中国南海西风加强,而中国30°N以北西风减弱,相应地东亚急流减弱;500 hPa上西欧脊加强且东欧大槽加深,伴随孟加拉湾北部南支槽加深而东亚大槽减弱,有利于欧洲中东部冷空气频繁向东南方向活动,并一直影响到中国西南部;850 hPa上缅甸、中南半岛、华南沿海的西南风距平,有利于孟加拉湾水汽向华南地区输送;上述大气环流异常有利于华南地区降水显著增加,长江上游地区气温下降特别是西南地区气温显著降低,东北地区气温升高;反之亦然。     

Analysis of fossil testate amoebae in Selisoo Bog,Estonia: local variability and implications for palaeoecological reconstructions in peatlands

Niinemets, E., Pensa, M. & Charman, D. J. 2010: Analysis of fossil testate amoebae in Selisoo Bog, Estonia: local variability and implications for palaeoecological reconstructions in peatlands. Boreas, 10.1111/j.1502‐3885.2010.00188.x. ISSN 0300‐9483. Local variability in decadal water‐table changes on an ombrotrophic peatland was explored using testate amoebae analysis of near‐surface peats in an Estonian raised bog. The distribution of testate amoebae assemblages was studied along the gradient from hummock to hollow in the upper 30‐cm layer of peat. As expected, testate amoebae assemblages in different micro‐ecotypes from hummock to hollow, even as close as 10 m apart, are distinctly different. Past water‐table change was reconstructed by applying a transfer function based on modern samples from throughout Europe. Results show a decline in water level from the mid‐late 20th century on Selisoo bog in all profiles from the different micro‐ecotypes. However, the absolute water‐table depths and amplitudes of fluctuations vary between reconstructions from different sampling micro‐ecotypes. Cores were correlated using changes in non‐mire pollen concentrations down‐core, but it was not possible to correlate minor changes in water‐table owing to non‐contiguous sampling and variable accumulation rates. We conclude that different microtopes show the same decadal trends in relative water‐table change but that the absolute magnitude of change may be more variable locally. It is important that reconstructed palaeohydrological changes in bogs consider changes in bog micro‐ecotypes, and their variation over time, as this may alter the sensitivity of an individual record to drivers such as climate change. Comparison and compilation of data from parallel cores from different micro‐ecotypes and/or different sites are likely to provide more robust reconstructions.     

Organic geochemical characterization and depositional paleoenvironments of the Devonian strata in Guizhong region,Guangxi, China

Devonian strata in the Guizhong region, Guangxi, China consist mainly of marine deposition carbonates (limestones and dolomites) as well as restricted clastic rocks. The strata thickness is measured as 2041m and classified into 14 formations. An integrated field geological, petrographic, sedimentological, palaeobiological, and geochemical study of these strata reveals that the depositional paleoenvironments were carbonate tidal flat, restricted platform, open platform, shelf, platform margin slop, and algal herm. The total organic carbon (TOC) of sedimentary organic matter ranges between 0.07% and 1.96% with average of 0.21%. The organic matter types are Type I and Type III. The vitrinite reflectance (R ₀) of kerogen ranges between 0.99% and 2.03%, indicating the maturated and highly maturated stages. The analytical results of the representative samples collected from shelf and subtidal facies show that the differences of organic matter type and biological diagnostic compounds are related to the types of source rocks deposited in different paleoenvironments.