Field report: Sailing around the exhumed roots of the Mesozoic Patagonian paleo-accretionary wedge(Diego de Almagro Island,Chile)     

Samuel Angiboust  Jesus Mu?oz 《地学前缘(英文版)》2018,9(5):1591-1594

We undertook a boat expedition to explore the geological framework of a very remote, lesser-known island, in the Chilean Patagonia: the Diego de Almagro Island(latitude S51°330'). This uninhabited, ca.400 km~2 Island is one of the very rare exposures of the Mesozoic accretionary subduction complex along the Chilean margin. Unstable weather, strong winds, steep topography, and very dense vegetation make an on-land mission difficult. Careful preparation based on high-resolution satellite images is advised to optimize shore access and minimize risks of injury. Despite a relatively important degree of regional reequilibration of metamorphic assemblages due to sluggish exhumation through the forearc crust, our results have shown that the island is composed of a nappe stack of ocean-floor derived slivers of metasedimentary units that exhibit very different pressure-temperature-time paths during burial by subduction under the Chilean margin and subsequent exhumation. These rocks are witness to a complex thermal evolution of the subduction zone between Jurassic and Cretaceous times from granulite facies to blueschist facies conditions as well as multiple episodes of accretion at ca. 35 -40 km in depth for almost100 Ma over the Mesozoic era.  相似文献   

Spatio-temporal evolution and dynamic simulation of the urban resilience of Beijing-Tianjin-Hebei urban agglomeration     

Mu  Xufang  Fang  Chuanglin  Yang  Zhiqi 《地理学报(英文版)》2022,32(9):1766-1790

Journal of Geographical Sciences - The continuous growth of urban agglomerations in China has increased their complexity as well as vulnerability. In this context, urban resilience is critical for...  相似文献   

Similarities between optimal precursors for ENSO events and optimally growing initial errors in El Niño predictions     

Mu Mu  Yanshan Yu  Hui Xu  Tingting Gong 《Theoretical and Applied Climatology》2014,115(3-4):461-469

With the Zebiak–Cane model, the relationship between the optimal precursors (OPR) for triggering the El Niño/Southern Oscillation (ENSO) events and the optimally growing initial errors (OGE) to the uncertainty in El Niño predictions is investigated using an approach based on the conditional nonlinear optimal perturbation. The computed OPR for El Niño events possesses sea surface temperature anomalies (SSTA) dipole over the equatorial central and eastern Pacific, plus positive thermocline depth anomalies in the entire equatorial Pacific. Based on the El Niño events triggered by the obtained OPRs, the OGE which cause the largest prediction errors are computed. It is found that the OPR and OGE share great similarities in terms of localization and spatial structure of the SSTA dipole pattern over the central and eastern Pacific and the relatively uniform thermocline depth anomalies in the equatorial Pacific. The resemblances are possibly caused by the same mechanism of the Bjerknes positive feedback. It implies that if additional observation instruments are deployed to the targeted observations with limited coverage, they should preferentially be deployed in the equatorial central and eastern Pacific, which has been determined as the sensitive area for ENSO prediction, to better detect the early signals for ENSO events and reduce the initial errors so as to improve the forecast skill.  相似文献   

条件非线性最优扰动法在大气与海洋目标观测研究中的应用   总被引：3，自引：0，他引：3  

穆穆  王强  段晚锁  姜智娜 《气象学报》2014,72(5):1001-1011

对近年来用条件非线性最优扰动法研究大气与海洋目标观测问题的部分工作进行了总结,主要涉及厄尔尼诺-南方涛动（ENSO）事件、黑潮路径变异事件以及阻塞事件。通过研究这些事件发生的最优前期征兆（OPR）和最快增长初始误差（OGE）,发现这些事件的最优前期征兆和最快增长初始误差分别具有空间的高度相似性及其伴随的局地性特征。理想回报试验表明,如果在ENSO事件和黑潮路径变异事件的最快增长初始误差和最优前期征兆所确定的扰动大值区减小初始场误差,上述事件的预报技巧会大幅度提高;最优前期征兆和最快增长初始误差的空间相似性使得在同一敏感区域增加额外观测,不仅有助于捕捉上述异常事件的前期信号,还可以有效减小初始误差,从而提高对该事件的预报技巧。阻塞事件爆发的最优前期征兆和最快增长初始误差的空间相似性和局地性特征在其目标观测研究中的应用,应该是深入研究的课题。  相似文献   

Comparison of sparse‐grid geometric and random sampling methods in nonlinear inverse solution uncertainty estimation     

Michael J. Tompkins  Juan Luis Fernández Martínez  Zulima Fernández Muñiz 《Geophysical Prospecting》2013,61(1):28-41

A new uncertainty estimation method, which we recently introduced in the literature, allows for the comprehensive search of model posterior space while maintaining a high degree of computational efficiency. The method starts with an optimal solution to an inverse problem, performs a parameter reduction step and then searches the resulting feasible model space using prior parameter bounds and sparse‐grid polynomial interpolation methods. After misfit rejection, the resulting model ensemble represents the equivalent model space and can be used to estimate inverse solution uncertainty. While parameter reduction introduces a posterior bias, it also allows for scaling this method to higher dimensional problems. The use of Smolyak sparse‐grid interpolation also dramatically increases sampling efficiency for large stochastic dimensions. Unlike Bayesian inference, which treats the posterior sampling problem as a random process, this geometric sampling method exploits the structure and smoothness in posterior distributions by solving a polynomial interpolation problem and then resampling from the resulting interpolant. The two questions we address in this paper are 1) whether our results are generally compatible with established Bayesian inference methods and 2) how does our method compare in terms of posterior sampling efficiency. We accomplish this by comparing our method for two electromagnetic problems from the literature with two commonly used Bayesian sampling schemes: Gibbs’ and Metropolis‐Hastings. While both the sparse‐grid and Bayesian samplers produce compatible results, in both examples, the sparse‐grid approach has a much higher sampling efficiency, requiring an order of magnitude fewer samples, suggesting that sparse‐grid methods can significantly improve the tractability of inference solutions for problems in high dimensions or with more costly forward physics.  相似文献   

渤海湾西岸的几道贝壳堤   总被引：2，自引：1，他引：1  

岳军  Dong yue  张宝华  耿秀山  刘雪松  赵希涛  牟林  张百鸣  韩芳 《地质学报》2012,86(3):522-534

渤海湾西岸出露或埋藏了多道贝壳堤,通过地质调查发现:贝壳堤的平面分布结构是沿着(或随着)渤海湾海岸由老至新(从岸—海)与海岸呈大致平行排列。贝壳堤的划分方案有两种,一种是从新至老,另一种是从老至新,本文采取后一种划分方法:即第Ⅰ道(老)—第Ⅵ道(新)贝壳堤。本文对每道贝壳堤的物质(岩性特征)组成与堆积特征进行了描述(图2～图7);对贝壳堤的几何形态特征进行了数理统计(表2);对贝壳堤形成的年代特征进行了对比分析(表3);对贝壳堤的生物组合特征等资料进行了归纳和整理;对贝壳堤的分道方案进行了对比分析(表1),揭示了贝壳堤的赋存状态、形成的年代及第Ⅰ道—第Ⅵ道贝壳堤所处的潮位变化(图8)。以形成贝壳堤这一独特的地质载体为基础,试图从渤海湾宏观整体的角度分析并揭示贝壳堤的成因机制(表4,图9),笔者认为广义的渤海湾是内陆的半泻湖(海),也可以视为局部海:山东庙岛列岛—辽东半岛构成了渤海的障壁海岸,在障壁海岸这样的自然地理和地貌条件下,通过大量的资料综合分析认为只有障壁海岸才是形成"科珀河型三角洲与喙状三角洲"的必然条件,而"科珀河型三角洲与喙状三角洲类型"等是形成障壁砂坝(障壁岛,障壁滩)—贝壳堤的或然条件,这就是贝壳堤成因的主要机制。  相似文献   

热带太平洋海洋环流与暖池的结构特征、变异机理和气候效应   总被引：3，自引：0，他引：3  

王凡  胡敦欣  穆穆  王启  何金海  朱江  刘志宇 《地球科学进展》2012,27(6):595-602

热带西太平洋暖池是引发强烈的大气对流、驱动Walker环流和Hadley环流系统的主要热源之一,对全球、尤其是东亚气候有重要影响。针对我国在提升气候预测水平方面的重大和迫切需求,国家重点基础研究发展计划项目"热带太平洋海洋环流与暖池的结构特征、变异机理和气候效应"于2011年7月正式立项。项目拟解决的关键科学问题包括:①调控暖池形成和变异的海洋环流多尺度相互作用过程;②海洋动力过程在暖池热盐结构变异中的作用及其机理;③暖池变异对不同类型El Nio影响机理的异同和对东亚季风变异的调制机理。围绕上述关键科学问题,项目将以暖池变异为中心,关注影响和控制暖池结构与变异的关键海洋过程,以及暖池海气相互作用影响ENSO循环、东亚季风年际变异的过程和机理,重点组织开展以下3个方面有针对性的调查研究:①热带太平洋环流和暖池的结构和变异特征;②热带太平洋环流与暖池相互作用的关键过程和机理;③暖池变异的海洋—大气耦合过程及其气候效应。在此基础上,项目将力争阐明暖池影响东亚季风和我国气候变异的过程、机理与敏感区,改进模式的混合参数化方案,提出有效提高ENSO预报技巧的同化方案,为我国短期气候预测能力的提高提供科学支撑。  相似文献   

湘西花垣排碧寒武系花桥组上段—车夫组沉积环境的探讨   总被引：1，自引：0，他引：1  

梁薇  牟传龙  周恳恳  葛祥英 《地质论评》2012,58(2):259-267

湘西排碧位于中上扬子陆块的东南缘,前人认为在寒武纪第三世时期该地区位于以各种类型的"碳酸盐重力流沉积"发育为显著特征的"台缘斜坡相带"内,其主要岩石类型为泥质条带灰岩及砾屑灰岩。本文通过对花桥组上段—车夫组典型沉积物的岩石组分及沉积构造进行详细研究,发现条带灰岩并非泥质条带灰岩,而是由灰岩条带——颗粒灰岩、泥晶灰岩与粉砂质条带——粉砂质灰岩、纹层状含炭质粉砂质灰岩互层组成,表现出内源碳酸盐沉积物与陆源碎屑沉积物混积以及陆棚环境沉积物的典型特征。砾屑灰岩及伴生岩石组合发育丘状(洼状)交错层理等众多风暴成因的沉积构造,为具有不同风暴沉积序列的风暴沉积物。此外,花桥组上段—车夫组沉积物中含各种藻类等浅水生物及大量三叶虫骨刺。因此,认为花桥组上段—车夫组的沉积环境应为正常浪基面以下、风暴浪基面以上,受周期性强风浪作用影响的混积陆棚环境。  相似文献   

山东平邑盆地古近系湖相微生物碳酸盐岩形成机理^*          下载免费PDF全文

唐鑫萍  黄文辉  邓宏文  王文勇  穆娜娜 《古地理学报》2012,14(3):355-364

微生物碳酸盐岩是当前沉积学的研究热点之一,但关于古近系湖相微生物碳酸盐岩的报道还非常少。为探讨山东平邑盆地古近系官庄组中段湖相微生物碳酸盐岩的形成机理,笔者进行了野外实测以及室内偏光显微镜和扫描电镜观察。研究结果认为：（1）研究区微生物碳酸盐岩主要有核形石、叠层石和凝块石;（2）在核形石、叠层石和凝块石内部均发现了球状微生物化石、席状体和凝块状泥晶等微生物成因的显微组构,表明了它们形成过程中共同的生长、粘结和钙化等微生物作用;（3）微生物作用对环境变化比较敏感,水体较小、变化频繁的湖泊环境,对微生物碳酸盐岩结构和形态的发育有很大影响;核形石、叠层石和凝块石的形成环境大致呈现出水动力依次减弱、陆源碎屑物质依次减少、水深依次加大的规律;（4）提出了研究区微生物碳酸盐岩的成因模式,认为这3种微生物碳酸盐岩正是以微生物活动为共同基础,在不同的环境条件下形成的。  相似文献   

鄂尔多斯盆地煤炭基地含水层及其保护研究     

马秀芬  翟立娟  傅耀军  唐燕波  李七明  苗建  穆金霞  李岩 《中国煤炭地质》2012,(8):36-42

鄂尔多斯盆地周边分布着神东、陕北、黄陇和宁东四个大型煤炭基地,煤炭资源丰富,但开采利用程度低,是我国＂十二五＂期间重点开发的矿区。在系统分析盆地内侏罗系煤层顶板白垩系裂隙含水层和第四系萨拉乌苏组孔隙含水层富水性的基础上,揭示了含水层与煤层的叠置关系;以煤炭开采破坏含水层、煤层与含水层距离、煤层与地表距离、含水层富水性为依据,将含水层破坏模式划分为：破坏顶板萨拉乌苏组含水层亚区、煤层埋藏浅破坏顶板含水层及生态环境亚区、破坏顶板含水层富水性较好亚区、破坏顶板含水层富水性较弱亚区,并对含水层破坏程度进行了分区评价;最后提出了含水层保护措施,为煤炭开采后的防治水工作提供了依据。  相似文献