• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文学位 >Changements climatiques et variations du champ magnetique terrestre dans le sud de la Patagonie (Argentine) depuis 51 200 ans reconstitues a partir des proprietes magnetiques des sediments du lac Laguna Potrok Aike.
【24h】

Changements climatiques et variations du champ magnetique terrestre dans le sud de la Patagonie (Argentine) depuis 51 200 ans reconstitues a partir des proprietes magnetiques des sediments du lac Laguna Potrok Aike.

机译：从拉古纳·波特罗克·艾克（Laguna Potrok Aike）沉积物的磁学性质重建了巴塔哥尼亚（阿根廷）南部51200年以来的气候变化和变化。

获取原文
获取原文并翻译 | 示例
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

Rock magnetism is influenced by climate and by the Earth's magnetic field. The goal of this thesis is to use the rock magnetic properties of the long sedimentary sequence from the lake Laguna Potrok Aike (106 m, 51200 cal BP) to derive paleomagnetic and paleoclimatic records in a key area of the Southern Hemisphere that is poorly documented. Laguna Potrok Aike (52°S, 70°W) is located in southeastern Patagonia (Argentina) in the path of the strong Southern Hemisphere westerly winds and in the source area of the dust deposited in Antarctica during Glacial periods. The lake geographical location is therefore ideal to reconstruct past changes in aeolian activity and climate changes in Patagonia. It is also a key location to reconstruct past changes of the geomagnetic field because the Southern Hemisphere is significantly under-documented relative to the Northern Hemisphere. In addition, the proximity of the South Atlantic Anomaly (SAA) as well as the Southern Hemisphere high flux lobes could allow identifying differences in the paleomagnetic field evolution in southern South America relative to the much more documented Northern Hemisphere. For his strong potential to provide high-resolution climatic, aeolian and paleomagnetic records beyond the last climatic transition, the maar lake Laguna Potrok Aike was drilled in the framework of the International scientific Continental Drilling Program (ICDP) for the Potrok Aike maar lake Sediment Archive Drilling prOject (PASADO). In this thesis, high-resolution rock-magnetic and physical properties are used in order to reconstruct paleoclimate and paleomagnetic records from the southernmost part of South America.;In the second chapter, rock-magnetic proxies of dust and wind intensity since 51200 cal BP are constructed. The combined use of rock magnetism and grain size data allowed identifying the median destructive field of the isothermal remanent magnetisation (MDFIRM) as best reflecting silt-sized magnetite typically transported by wind in suspension over short distances. The MDF IRM displays similar variability than other wind intensity proxies derived from marine and lacustrine sediments, peat bug and speleothem records from Patagonia since the last climatic transition and from the Southern Hemisphere since 51200 cal BP. In addition, estimation of the flux of magnetite to the lake, investigation of the grain size influence on magnetic susceptibility and comparison with distal Patagonian dust records from the Southern Ocean and Antarctica indicate that the magnetic susceptibility signal from Laguna Potrok Aike is a dust record at the multi-millennial scale.;In the third chapter, rock-magnetic proxies of runoff events associated with extreme precipitation and permafrost melt since 51200 cal BP are presented. The runoff events are identified by the presence of high coercivity magnetic mineral (such as hematite and goethite) which its pedogenic origin is inferred from geological, limnological, stratigraphic and climatic evidence. The runoff events are generally associated with mass movement deposits during time of enhanced lake productivity in Laguna Potrok Aike and are also coeval within the limit of the chronology to warm atmospheric conditions recorded in Antarctica. In addition, we show that the authigenic formation of iron sulfide such as greigite is strictly associated to reworked sands and tephra layers providing the required suboxic conditions and dissolved sulfate.;As a whole, rock magnetism of the sediment from Laguna Potrok Aike provides a high quality full-vector paleomagnetic record as well as rock-magnetic proxies of past climate changes in southeastern Patagonia that are also associated with climate changes in Antarctica.;In the first chapter, the full-vector paleomagnetic record (inclination, declination and relative paleointensity) derived from the sediments of Laguna Potrok Aike. A grain size influence on the relative paleointensity record (NRM/ARM) was corrected using the median destructive field of the natural remanent magnetisation (MDFNRM). Full-vector comparison of the new paleomagnetic record with other records from southern South America, elsewhere in the Southern Hemisphere, as well as dipole field models and compilations reveal similar millennial-scale variability. The Laschamp geomagnetic excursion and possibly the Mono Lake as well as the Hilina Pali excursions are recorded and suggest the global nature of these events. Nevertheless comparison with the Lake Baikal and Biwa records located on the opposite side of the globe in Siberia and Japan respectively reveals a different behaviour at ca. 46000 cal BP in Laguna Potrok Aike and in southern South America, hinting at a non-dipolar origin.;Keywords: [Paleomagnetism, sediment magnetism, paleoclimatology, Laguna Potrok Aike, Patagonia, Southern Hemisphere, millennial- to centennial-scale variability, last Glacial period, Holocene, wind intensity].
机译：岩石的磁性受气候和地球磁场的影响。本论文的目的是利用拉古纳·波特罗克·艾克湖（106 m，51200 cal BP）的长沉积序列的岩石磁学性质，得出南半球关键地区的古磁和古气候记录，但文献记载很少。 Laguna Potrok Aike（52°S，70°W）位于巴塔哥尼亚东南部（阿根廷），在强南半球西风的路径上以及冰川时期沉积在南极洲的尘埃源区域。因此，该湖的地理位置非常适合重建巴塔哥尼亚的风沙活动和气候变化的过去变化。它也是重建地磁场过去变化的关键位置，因为相对于北半球，南半球的文献资料明显不足。此外，南大西洋异常（SAA）以及南半球高通量波瓣的邻近性，可以使南美洲南部的古磁场演化相对于文献更多的北半球有所区别。由于其在上一次气候转变之后提供高分辨率的气候，风沙和古磁记录的强大潜力，在国际科学大陆钻探计划（ICDP）的框架内为Potrok Aike maar湖沉积物档案馆钻了Maar Laguna Potrok Aike湖钻井项目（PASADO）。本文利用高分辨率的岩石磁和物理性质，以重建南美最南端的古气候和古磁记录。被建造。岩石磁性和粒度数据的结合使用可以将等温剩余磁化强度（MDFIRM）的中值破坏场确定为最佳反射粉砂大小的磁铁矿，通常通过风在短距离内以悬浮方式运输。 MDF IRM显示的变化与其他自上次气候转变以来来自巴塔哥尼亚的海洋和湖相沉积物，泥炭臭虫和speleothem记录以及自51200 cal BP以来的南半球的其他风强度代理相似。此外，估算磁铁矿向湖泊的通量，研究颗粒大小对磁化率的影响，并与南大洋和南极洲的巴塔哥尼亚远洋尘埃记录进行比较，表明来自拉古纳·波特罗克·艾克的磁化率信号是一个尘埃记录。第三章介绍了自51200 cal BP以来与极端降水和多年冻土融化有关的径流事件的岩石磁代理。径流事件是通过存在高矫顽力磁性矿物（例如赤铁矿和针铁矿）来确定的，其成岩作用是根据地质，岩相，地层和气候证据推断出来的。在拉古纳·波特罗克·艾克的湖泊生产力提高的时期，径流事件通常与大规模的运动沉积有关，在南极洲记录的温暖大气条件的年代学范围内，径流事件也是同时发生的。此外，我们证明了诸如铁辉石等硫化铁的自生形成与提供所需的亚氧条件和溶解的硫酸盐的返工砂和特非拉层有严格的联系;总体而言，拉古纳Potrok Aike沉积物的岩石磁化强度很高。全矢量古磁记录以及南巴塔哥尼亚东南部过去气候变化的岩石磁代理，也与南极洲的气候变化有关。在第一章中，全矢量古磁记录（倾角，偏角和相对古强度）源自拉古纳Potrok Aike的沉积物。使用自然剩余磁化强度的中值破坏场（MDFNRM）校正了晶粒尺寸对相对古强度记录（NRM / ARM）的影响。新的古磁记录与南美洲南部，南半球其他地方的其他记录的全矢量比较，以及偶极子场模型和汇编都显示出类似的千年尺度变化。记录了Laschamp地磁游览以及可能的Mono湖以及Hilina Pali游览，这表明了这些事件的全球性。然而，与分别位于西伯利亚和日本的地球另一侧的贝加尔湖和琵琶湖的记录进行比较后，发现大约在西伯利亚。拉古纳·波特罗克·艾克和南美洲南部地区的46000 cal BP，暗示着非偶极起源。冰川期，全新世，风强度]。

著录项

  • 作者

    Lise-Pronovost, Agathe.;

  • 作者单位

    Universite du Quebec a Rimouski (Canada).;

  • 授予单位 Universite du Quebec a Rimouski (Canada).;
  • 学科 Environmental science.;Geology.;Electromagnetics.
  • 学位 Ph.D.
  • 年度 2014
  • 页码 236 p.
  • 总页数 236
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号