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

别林斯豪森板块位于南极西部冰原的很大一部分之下，它拥有几个深切的槽，这些槽被解释为南极西部裂谷系统的分支，这是地球上最大的大陆裂谷结构之一。除了靠近海槽的几处冰暴外，这些裂谷分支完全被几公里厚的冰覆盖，阻碍了直接的地质调查。海沟将南太平洋与南极洲大陆内部连接起来，为温暖的海洋深水提供了通道，这导致了上覆冰盖的基底融化。破冰船北极星号为我们提供了实地工作和样本收集的机会，以调查南极洲的这一偏远地区。除了沿海的冰暴外，我们还将从隐藏在冰下的区域收集材料，这些材料来自流入别令斯豪森海的冰川出口的近海碎屑沉积物。样品将通过U/Pb、裂变径迹和(U- th)/He组合分析进行研究。为了有效地对碎屑矿物进行(U-Th)/He分析，我们将采用激光烧蚀(U-Th)/He定年的新技术。将讨论两个主要问题：(i)活动的时间、模式（连续的还是偶发的）和不同裂谷分支的运动学关系。这些结果将有助于理解迄今为止缺乏约束的大陆裂谷系统，并且还将提供信息，因为通过深裂谷连接海洋领域和大陆内部的当前结构何时可能存在于过去。这反过来又提供了关于南极西部冰盖过去脆弱性的信息。别令斯豪森地区的构造演化。板块构造重建表明，别令斯豪森板块的构造历史与相邻的阿蒙森板块非常不同，后者自~100 Ma以来一直处于裂谷边缘，而别令斯豪森板块至少在始新世之前一直处于活动边缘位置。这些不同的构造环境只是没有充分地纳入当前的古地形模式。然而，了解南极洲的地形演变是非常重要的，因为地形的存在是在地质过去的温暖气候下允许南极西部冰川作用的先决条件。我们的新数据将与先前发表的来自西南极洲和横贯南极山脉的热年代学数据进行汇编，部分数据将进行重新建模，以获得内部一致的挖掘模式，并结合近海地震和沉积学数据。由此，我们将生成地图，可视化不同时间片的陆上和海上剥蚀和埋藏模式，为理解源-汇关系、排水模式和精细的古地形模型提供一个全面的数据库。

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.