Dynamic early Holocene vegetation development on the Faroe Islands inferred from high-resolution plant macrofossil and pollen data

Vegetation dynamics during the earliest part of the Holocene (11,250-10,250 cal yr BP) have been reconstructed from a lacustrine sequence on Sandoy, the Faroe Islands, using detailed plant macrofossil and pollen evidence. The plant macrofossils suggest the initial vegetation was sparse herb and shrub tundra, with Salix herbacea and open-ground species, followed by the development of a denser and more species-rich arctic heathland after 11,150 cal yr BP. Despite high pollen values for Betula nana, macrofossils are rare. The bulk of the macrofossils recorded are S. herbacea and Empetrum leaves with numerous herb taxa and an abundance of Racomitrium moss. Conditions start to change around 10,800 cal yr BP, with increased catchment erosion and sediment delivery to the lake from ca. 10,600 cal yr BP, and a transition to alternating Cyperaceae and Poaceae communities between ca. 10,450 and 10,250 cal yr BP. This vegetation change, which has been recorded throughout the Faroes, has previously been interpreted as a retrogressive shift from woody shrubs to a herbaceous community. The detailed plant macrofossil data show the shift is the replacement of an Empetrum arctic heathland by grassland and moist sedge communities. These taxa dominate the modern landscape.     

The Permian mafic intrusive events in the northwestern margin of the Tarim Basin and their tectonic significanceSCIEI北大核心CSCD

塔里木大火成岩省是我国境内发现的两个重要的二叠纪大火成省之一,不仅有大规模的溢流相玄武岩喷发,还有复杂多样的侵入岩及其组合。以往的研究主要集中在二叠系等显生宙地层发育区,对于前寒武系等古老层系中是否存在二叠纪岩浆侵入未引起重视。本文通过野外地质调查,在阿克苏地区前寒武系中识别出数条侵入南华系的基性岩墙和较大规模侵入震旦系的基性岩床。岩墙、岩床与围岩之间均显示出典型的侵入接触关系,包括岩体内部结晶粗、边部结晶细的淬冷边结构、岩床顶底面显著的切层现象以及包裹围岩团块等;显微镜下观察表明,辉绿岩具有典型的辉绿结构和嵌晶含长结构。锆石U-Pb年代学结果表明,侵入下震旦统的辉绿岩岩床和侵入南华系的辉绿岩岩墙的侵位时代在误差范围内基本一致,约为290Ma。岩石地球化学特征表明,辉绿岩岩床具有与洋岛玄武岩(OIB)相似的稀土及微量元素配分模式,结合Sr-Nb-Pb同位素测试结果,认为它们来源于碳酸盐化的富集型岩石圈地幔部分熔融,而辉绿岩岩墙具有Nb、Ta、Zr、Hf等负异常的地球化学特征,可能来自曾被俯冲相关流体/熔体交代的岩石圈地幔源区。本文的早二叠世辉绿岩岩床和岩墙的形成时代、岩浆源区和岩浆演化...     

广西玉林北均塘组腕足动物群的发现及意义

首次报道了广西玉林林木北均塘组校深水相腕足动物群。论证了其较深水相的性质；讨论了部分种的演化；建立了四个腕足生物带；简述了与笔石带的关系并进行了国际对比；确定其时代为晚洛赫柯夫－早布拉格早期，得出腕足动物集群具有快速迁移能力的结论；鱼化石的发现也为我国华南早泥盆世早期海相与陆相地层的对比提出了线索。     

Rock associations and their spatial-Temporal variations of the early mesozoic igneous rocks in the NE Asia: Constraints on the initial subduction timing of the paleo-pacific plate北大核心CSCD

This paper summarizes rook associations and spatial-Temporal variations of the early Mesozoic igneous rocks in the NE Asia, with the aim of revealing the initial subduction timing of the Paleo-Pacific Plate beneath the Eurasia, and the relationships between the early Mesozoic magmatisms and the Paleo-Asian tectonic system, Mongol-Okhotsk tectonic system, and amalgamation of the Yangtze and North China cratons. Dating results indicate that the early Mesozoic magmatisms in the NE Asia can be subdivided into three stages, i.e., Early-Middle Triassic, Late Triassic, and Early Jurassic. The early Mesozoic calc-Alkaline magmatisms within the Erguna Massif reveal southward subduction of the Mongol-Okhotsk oceanic plate. The Triassic alkaline and bimodal magmatisms within the northern margin of the North China Craton indicate an extensional environment related to the final closure of the Paleo-Asian Ocean. The Late Triassic A-Type rhyo- lites and bimodal magmatisms, together with the Late Triassic stable sedimentary rocks, in eastern Heilongjiang-Jilin provinces, reveal an extensional environment and passive continental margin setting, whereas the Early Jurassic calc-Alkaline magmatisms and its compositional variations, together with the coeval accretionary complex, reveal the onset of the Paleo- Pacific plate beneath the Euirasian continent.     

东昆仑大干沟火山岩SHRIMP锆石U-Pb测年及其地质意义

东昆仑大干沟以北地区造山后形成的牦牛山组磨拉石建造不整合覆盖于前泥盆系之上,其形成时代对限定柴达木盆地加里东造山作用的结束时间及晚古生代裂解作用的开始时间具有重要意义。应用单颗粒锆石离子探针质谱仪(SHRIMP)方法,对牦牛山组上部火山岩段的样品进行精确的锆石U-Pb测年。结果表明,牦牛山组上段火山岩样品DG01和DG02中的岩浆锆石206Pb/238U平均年龄分别为403.6±5.1Ma和409±3.4Ma。综合前人研究认为,造山后牦牛山组伸展型磨拉石的形成时代为晚志留世-早泥盆世,限定了晚古生代裂解的开始时间,也意味着早古生代加里东造山运动在晚志留世-早泥盆世之前已经结束。     

基于危险度区划的县级区域降雨引发滑坡的风险预警方法——以四川省米易县降雨滑坡为例

降雨滑坡预警在世界上开展广泛,但对小区域的降雨滑坡风险进行预警尚不多见。以通用的风险定义为基础,首先对目标区域——四川省米易县的地质灾害进行调查,以典型滑坡进行反演,获得灾害的本底因素,按贡献率权重叠加法进行危险度分区;通过对承灾体的调查确定承灾对象,并将各承灾对象按密度由行政界限向1km×1km的网格单元转化后叠加形成易损度分区。二者相乘完成风险分区。对研究区域近5年逐日降雨数据与172条地质灾害记录进行分析,按前期日降雨量模型得到降雨阈值,根据滑坡空间概率和降雨引发滑坡的时间概率叠加的结果,得到研究区域的降雨滑坡概率,对照风险分区,完成风险预警。     

论辽宁锦西杨家杖子杂岩体的岩浆成因演化及成矿作用

杨家杖子杂岩体中的二长闪长岩代表一种母岩浆,它是燕山早期库拉板块向欧亚板块下俯冲所产生的,并汇聚上升的安山质岩浆。粗粒似斑状二长花岗岩、细粒似斑状二长花岗岩和(碱长)花岗斑岩是二长闪长岩浆在7km深、弱还原环境、氧逸度为10~(-8)～10~(-10)Pa、1200°～1250℃的岩浆房中经结晶分异作用的派生物。以后,这些岩浆相继上侵,定位于2.5km深处。由这些岩浆岩侵入体所引起的镁夕卡岩、钙夕卡岩和岩浆期后酸性热液淋滤蚀变非常发育。只有来自细粒似斑状二长花岗岩和(碱长)花岗斑岩岩浆、富含Mo的酸性热液沿着裂隙侵入夕卡岩中,在240～330℃时,才形成Mo矿床。此种酸性热液也沿着裂隙侵入细粒似斑状二长花岗岩和(碱长)花岗斑岩中,而形成细脉浸染Mo矿床。因此,杨家杖子Mo矿床属于斑岩-夕卡岩型。     

3. Solar System Formation and Early Evolution: the First 100 Million Years

The solar system, as we know it today, is about 4.5 billion years old. It is widely believed that it was essentially completed 100 million years after the formation of the Sun, which itself took less than 1 million years, although the exact chronology remains highly uncertain. For instance: which, of the giant planets or the terrestrial planets, formed first, and how? How did they acquire their mass? What was the early evolution of the “primitive solar nebula” (solar nebula for short)? What is its relation with the circumstellar disks that are ubiquitous around young low-mass stars today? Is it possible to define a “time zero” (t ₀), the epoch of the formation of the solar system? Is the solar system exceptional or common? This astronomical chapter focuses on the early stages, which determine in large part the subsequent evolution of the proto-solar system. This evolution is logarithmic, being very fast initially, then gradually slowing down. The chapter is thus divided in three parts: (1) The first million years: the stellar era. The dominant phase is the formation of the Sun in a stellar cluster, via accretion of material from a circumstellar disk, itself fed by a progressively vanishing circumstellar envelope. (2) The first 10 million years: the disk era. The dominant phase is the evolution and progressive disappearance of circumstellar disks around evolved young stars; planets will start to form at this stage. Important constraints on the solar nebula and on planet formation are drawn from the most primitive objects in the solar system, i.e., meteorites. (3) The first 100 million years: the “telluric” era. This phase is dominated by terrestrial (rocky) planet formation and differentiation, and the appearance of oceans and atmospheres.     

On the periodical structures in populations of galaxies and of clusters of galaxies

Analysing the distribution of the redshift of clusters of galaxies, obtained from the catalogue of SCHMIDT (1986), two already known periodical structures were confirmed and both periods were extended by a number of periods — approximately by two times (We elucidated 5 new periods in the first structure and 4 in the second.). The statistical significance of these structures was estimated to 0.01 in the first case and to 0.02 in the second one. Particularly, the second structure may be the largest known object in the Universe (about 900 Mpc at H = 75 km s^-1 Mpc^-1). These results agree with the predictions of the axion-dominated early Universe. In addition, we discovered periodical structures of an another type — in luminosity functions of galaxies, which are members of rich clusters. Bei der Analyse des Katalogs von SCHMIDT (1986) wurden zwei periodische Strukturen in den Verteilungen der Rotverschiebungen von Galaxienhaufen festgestellt. In den beiden Strukturen wurden 5 bzw. 4 neue Perioden beobachtet, weshalb sich die Periodenzahl in jeder der beiden Strukturen etwa verdoppelt hat. Die statistische Signifikanzen dieser Strukturen wurden zu 0.01 und 0.02 abgeschätzt. Möglicherweise entspricht die zweite Struktur dem größten bekannten Objekt des Weltalls (etwa 900 Mpc bei H = 75 km s^-1 Mpc^-1). Diese Resultate stützen die Theorie eines axiondominierten frühen Universums. Außerdem wurden weitere periodische Strukturen in der Leuchtkraftfunktion von Galaxien aus reichen Galaxien-haufen entdeckt.     

基于数值模拟的渤海海域地震海啸危险性定量化研究

根据地震海啸产生的条件,结合渤海海域的地形特征、地质构造、地震学特征和历史地震及海啸记录对渤海海域潜在的地震海啸进行了数值模拟研究。分析了渤海可能引发地震海啸的震源区域,讨论了渤海发生海啸灾害的可能性。文中通过数值模拟再现了渤海历史上几次规模较大的地震事件可能引发的海啸情景,研究分析了可能的地震海啸在渤海及周边海域的传播过程及波动特征.地震海啸传播模型采用基于四叉树原理的自适应网格加密技术,有效解决了局部分辨率与计算效率之间的矛盾。数值计算包括地震海啸产生及传播过程。利用该模型对渤海潜在的地震海啸进行了数值计算,基于数值计算结果定量阐述了渤海海域潜在地震海啸对渤海局部岸段及北黄海沿岸的影响,给出了渤海可能地震海啸危险性划分;研究结果将为我国海啸危险性分析和海啸预警技术研究工作提供技术支持。