Collaborative Research: Exhumation of the Transantarctic Mountains: Constraints from (U-Th)/He Dating of Apatites

9909436 Farley这个奖项由极地项目办公室南极地质和地球物理项目提供，支持对横贯南极山脉干谷段的隆起历史进行调查。总体目标是进一步限制剥露历史的Transananaitic山脉使用新开发的磷灰石（U-Th）/He测年方法在垂直剖面收集的样品。这种方法，结合现有的磷灰石裂变径迹信息，将限制的速度和模式的折返横贯南极山脉，因为他们成立以来的裂谷侧翼隆起在新生代早期。这个项目将补充其他项目，并建立在以前的解释折返和构造历史确定磷灰石裂变径迹热年代学。它将弥补裂变径迹热年代学和宇宙成因表面暴露年代测定法确定的侵蚀率信息之间的差距，并将山脉的剥露历史与地貌演变结合起来。因此，该项目的成果将解决南极科学中的一个突出问题，即东南极冰盖的稳定性，以及从“温暖”的动态冰盖向寒冷的极地冰盖过渡的时间。与这个问题高度相关的是跨南极山脉的景观演化，因为许多不同的景观演化速度的证据已经被用来论证一个动态冰盖，直到上新世（“动态”冰盖模型）或中新世中期（“稳定”冰盖模型）。当然，了解东南极冰盖过去的稳定性或动态波动与气候记录的关系，这对了解目前的冰盖如何应对全球变暖至关重要。本项目的具体目标是确定磷灰石（U-Th）/从横贯南极洲的山脉前缘和穿越南极洲的构造纹理的一些垂直剖面，范围所有这些剖面的裂变径迹数据都已存在，磷灰石裂变径迹年龄在150-30 Ma之间。（U-Th）/He技术的更高精度和它在较低温度下记录信息的事实（封闭温度约为70摄氏度; He部分保留区的限制为40-85摄氏度）将允许更详细地检查TAM从约130 Ma到约20 Ma的折返历史。另一个方面是检查白垩纪折返记录的地区和裂变径迹剖面表明整个白垩纪的热稳定和构造稳定以及最小侵蚀时期的地区。在新生代早期，随着横贯南极山脉的隆起和形成，更快速的折返开始的时间变化也将被研究。

9909436 FarleyThis award, provided by the Antarctic Geology and Geophysics Program of the Office of Polar Programs, supports an investigation of the uplift history of the Dry Valleys segment of the Transantarctic Mountains. The overall goal is to further constrain the exhumation history of the Transantarctic Mountains by using the newly developed apatite (U-Th)/He dating method on samples collected in vertical profiles. This approach, combined with existing apatite fission track information will constrain the rate and patterns of exhumation across the Transantarctic Mountains since their inception as a rift-flank uplift in the early Cenozoic.This project will complement other projects and build on previous interpretations of the exhumation and tectonic history determined using apatite fission track thermochronology. It will bridge the gap between information on erosion rates determined from fission track thermochronology and from cosmogenic surface exposure dating and integrate the exhumation history of the mountains with their landscape evolution. As such, the results from this project will address an outstanding problem in Antarctic science; namely the stability of the East Antarctic Ice Sheet, and the timing of the transition from a "warm" dynamic ice sheet to a cold polar ice sheet. Highly relevant to this issue is the landscape evolution of the Transantarctic Mountains because many diverse lines of evidence for the rate of landscape evolution have been used to argue for a dynamic ice sheet up until either the Pliocene (the "dynamic" ice sheet model) or the middle Miocene (the "stable" ice sheet model). Understanding the past stability or dynamic fluctuations of the East Antarctic ice sheet with respect to the climate record is, of course, important for understanding how the present ice sheet may respond to global warming.The specific objective of this project is to determine apatite (U-Th)/He age versus elevation trends for a number of vertical profiles from locations within the Transantarctic Mountain front and across the structural grain of the range. Fission track data already exist for all of these profiles, with apatite fission track ages ranging from 150-30 Ma. The greater precision of the (U-Th)/He technique and the fact it records information at lower temperatures (closure temperature of ~70 degrees Celsius; limits of 40-85 degrees Celsius for the He partial retention zone) will allow examination of the exhumation history of the TAM in more detail from ca 130 Ma to ~20 Ma. Another facet is to examine areas where Cretaceous exhumation is recorded and areas where the fission track profiles indicate periods of thermal and tectonic stability and minimal erosion throughout the Cretaceous. The variation of timing of the onset of more rapid exhumation accompanying uplift and formation of the Transantarctic Mountains in the early Cenozoic will also be examined.