Exploring the hidden underbelly – tectononorphic evolution of the Bellingshausen Sea sector of West Antarctica

探索西南极洲别林斯高晋海区隐藏的弱点——构造演化

• 批准号: 510079091
• 负责人: Professor Dr. Frank Lisker
• 金额: --
• 依托单位: Fachgebiet Geodynamik der Polargebiete
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/510079091?language=en
• 关键词: Exploring; hidden; underbelly; tectononorphic; evolution

The Bellingshausen sector underlies a large part of the West Antarctic Ice Sheet, and it hosts several deeply incised troughs, which are interpreted as branches of the West Antarctic Rift System, one of the largest continental rift structures on Earth. Except for few nunataks close to the troughs, these rift branches are completely covered by km-thick ice, impeding direct geological investigations. The troughs connect the South Pacific with Antarctica´s continental interior, providing pathways for warm oceanic deep water, which causes basal melting of the overlying ice sheet. The ship icebreaker Polarstern provides us with the opportunity for field work and sample collection to investigate this remote part of Antarctica. In addition to the coastal nunataks, we will obtain material from the area hidden beneath the ice by collecting offshore clastic sediments from the glacial outlets draining into the Bellingshausen Sea. The samples will be studied by combined U/Pb, fission track and (U-Th)/He analysis. For efficiently including (U-Th)/He analysis on detrital minerals, we will apply the new technique of laser-ablation (U-Th)/He dating. Two main topics will be addressed: (i) Timing of activity, mode (continuous vs. episodic) and kinematic relationships of the different rift branches. The results will contribute to the understanding of this hitherto poorly constrained continental rift system, and will also provide information since when the current configuration connecting the oceanic realm with the continental interior via the deep rift troughs may have existed in the past. This in turn provides information on the past vulnerability of the West Antarctic Ice Sheet. (ii) Tectonomorphic evolution of the Bellingshausen sector. Plate tectonic reconstructions indicate that the tectonic history of the Bellingshausen sector was very different from that of the adjacent Amundsen sector, as the latter was situated along a rifted margin from ~100 Ma onwards, whereas the Bellingshausen sector remained in an active margin position until at least the Eocene. These different tectonic settings are only insufficiently incorporated into current paleotopographic models. However, understanding the topographic evolution of Antarctica is of major importance, because the existence of topography is the prerequisite to allow for West Antarctic glaciation under the warmer climate of the geological past. Our new data will be compiled with previously published thermochronology data from West Antarctica and the Transantarctic Mountains, partly remodelled for obtaining internally consistent exhumation patterns, and combined with offshore seismic and sedimentological data. From this we will generate maps which visualise patterns of onshore and offshore denudation and burial for various time slices, providing a comprehensive data base for understanding source-sink relationships, drainage patterns, and refined paleotopographic models.

别林斯高晋区位于西南极冰盖的大部分下方，拥有几个深切的海槽，这些海槽被解释为西南极裂谷系统的分支，西南极裂谷系统是地球上最大的大陆裂谷结构之一（除了靠近努纳塔克的少数努纳塔克裂谷结构）。这些裂谷分支完全被千米厚的冰覆盖，阻碍了直接的地质调查。南极洲的大陆内部为温暖的海洋深水提供了通道，从而导致了上覆冰盖的基底融化，破冰船“Polarstern”号为我们提供了实地工作和样本采集的机会，以调查南极洲的这一偏远地区。对于沿海的努纳塔克群岛，我们将通过收集排入别林斯高晋海的冰川出口的离岸碎屑沉积物来研究隐藏在冰层下的区域的材料。 U/Pb、裂变径迹和(U-Th)/He 分析为了有效地对碎屑矿物进行(U-Th)/He 分析，我们将应用激光烧蚀(U-Th)/He 测年新技术。将讨论两个主要主题：（i）不同裂谷分支的活动时间、模式（连续与间歇）和运动学关系。研究结果将有助于理解迄今为止约束较差的大陆裂谷系统。还将提供有关过去通过深裂谷连接海洋区域与大陆内部的结构的信息，这反过来又提供了有关南极西部冰盖过去脆弱性的信息。别林斯高晋扇区的演化过程表明，别林斯高晋扇区的构造历史与邻近的阿蒙森扇区有很大不同，因为后者所处的位置。从大约 100 Ma 开始，别林斯高晋扇区一直处于活跃的边缘位置，这些不同的构造环境还没有充分纳入当前的古地形模型中。然而，了解南极洲的地形演化至关重要。重要性，因为地形的存在是在过去地质气候温暖的情况下允许西南极冰川发生的先决条件。我们的新数据将与之前发布的数据一起汇编。来自西南极洲和横贯南极山脉的热年代学数据，经过部分改造以获得内部一致的折返模式，并将近海与地震和沉积学数据相结合，由此我们将生成可视化不同时间切片的陆上和近海剥蚀和埋藏模式的地图，提供。用于了解源汇关系、排水模式和精细古地形模型的综合数据库。