COLLABORATIVE RESEARCH:Exhumation of the Transantarcitic Mountains: Constraints from (U-Th)/He dating of apatites

合作研究：横贯南极山脉的挖掘：磷灰石 (U-Th)/He 测年的限制

• 批准号: 0002824
• 负责人: Paul Fitzgerald
• 金额: $ 6.5万
• 依托单位: Syracuse University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-06-01 至 2003-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0002824&HistoricalAwards=false
• 关键词: COLLABORATIVE; RESEARCH; Exhumation; Transantarcitic; Mountains

0002824FitzgeraldThis 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.

0002824菲茨杰拉德该奖项由极地项目办公室的南极地质和地球物理学项目提供，支持对横贯南极山脉干谷部分隆起历史的调查。总体目标是通过使用新开发的磷灰石 (U-Th)/He 测年方法对垂直剖面采集的样本进一步确定横贯南极山脉的折返历史。这种方法与现有的磷灰石裂变径迹信息相结合，将限制横贯南极山脉自新生代早期裂隙侧隆起以来的折返速度和模式。该项目将补充其他项目，并建立在以前对折返解释的基础上以及使用磷灰石裂变径迹热年代学确定的构造历史。它将弥合裂变径迹热年代学和宇宙成因表面暴露测年确定的侵蚀率信息之间的差距，并将山脉的折返历史与其景观演化结合起来。因此，该项目的结果将解决南极科学中的一个突出问题；即南极东部冰盖的稳定性，以及从“温暖”的动态冰盖过渡到寒冷的极地冰盖的时间。与这个问题高度相关的是横贯南极山脉的地貌演化，因为地貌演化速率的许多不同证据都被用来论证动态冰盖的存在，直到上新世（“动态”冰盖模型）或中新世（“稳定”冰盖模型）。当然，了解东南极冰盖相对于气候记录的过去稳定性或动态波动对于了解当前冰盖如何应对全球变暖非常重要。该项目的具体目标是确定磷灰石（U -Th)/He 年龄与海拔趋势的关系，来自横贯南极山脉前缘内的位置和整个范围的结构纹理的许多垂直剖面。所有这些剖面的裂变径迹数据均已存在，磷灰石裂变径迹年龄范围为 150-30 Ma。 (U-Th)/He 技术的精度更高，并且它在较低温度下记录信息（闭合温度约为 70 摄氏度；He 部分保留区的限制为 40-85 摄氏度），这将允许检查更详细地了解 TAM 从约 130 Ma 到约 20 Ma 的折返历史。另一个方面是检查记录白垩纪折返的区域以及裂变径迹剖面表明整个白垩纪热和构造稳定时期以及最小侵蚀的区域。新生代早期伴随着横贯南极山脉的隆升和形成，更快速的折返开始的时间变化也将得到研究。