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.

别林豪森地段是西南极冰盖的一大部分，它有几个被深深切割的海槽，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。除了靠近海槽的几个双峰外，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。这些海槽将南太平洋和南极洲的S大陆内陆连接起来，为温暖的海洋深水提供了通道，从而导致了上面的冰盖的底部融化。破冰船Polarstein号为我们提供了实地考察和采集样本的机会，以调查南极洲这一偏远地区。除了沿海的冰川，我们还将通过收集流入别林豪森海的冰川出口的离岸碎屑沉积物，从隐藏在冰下的区域获取物质。样品将进行U/Pb、裂变径迹和(U-Th)/He分析相结合的研究。为了有效地进行碎屑矿物的(U-Th)/He分析，我们将采用激光烧蚀(U-Th)/He测年新技术。将讨论两个主要主题：(I)活动的时间、模式(连续与幕式)和不同裂谷分支的运动学关系。这些结果将有助于理解这一迄今制约程度较低的大陆裂谷系统，并将提供信息，因为目前通过深裂谷连接大洋界和大陆内陆的构造可能在过去就存在过。这反过来又提供了有关西南极冰盖过去脆弱性的信息。(Ii)Bellinghausen部门的技术形态演变。板块构造重建表明，别林豪森地段的构造历史与邻近的阿蒙森地段有很大不同，阿蒙森地段从100 Ma开始就沿着裂谷边缘，而别林豪森地段至少在始新世以前一直处于活跃的边缘位置。这些不同的构造背景只是不能充分地纳入到当前的古地形模型中。然而，了解南极洲的地形演变是非常重要的，因为地形的存在是允许在地质历史上气候变暖的情况下进行南极西部冰川作用的先决条件。我们的新数据将与以前公布的南极洲西部和横贯北极山脉的热年代学数据汇编在一起，部分进行了改造，以获得内部一致的折返模式，并与近海地震和沉积学数据相结合。由此，我们将生成可视化各种时间片的陆上和近海剥蚀和埋藏模式的地图，为理解源-汇关系、排水模式和改进的古地形模型提供一个全面的数据库。