Identifying spatial variations in glacial catchment erosion with detrital thermochronology
Identifying spatial variations in glacial catchment erosion with detrital thermochronology
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DOI：
10.1002/2014jf003432
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发表时间：
2015-06-01
影响因子：
3.9
通讯作者：
Woodsworth, Glenn J.
中科院分区：
文献类型：
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作者：
Ehlers, Todd A.;Szameitat, Annika;Woodsworth, Glenn J.
由于难以到达冰川底部，此前要了解冰川作用期间冰川流域侵蚀的空间分布一直很困难。碎屑热年代学的最新进展为量化沉积物的源区海拔提供了一种新技术。这种方法利用热年代计冷却年龄随海拔升高而增加的趋势，为侵蚀海拔提供了一种沉积物示踪剂。我们将该技术应用于不列颠哥伦比亚省冰川作用强烈的沃丁顿山地区的蒂德曼冰川。从蒂德曼冰川现代冰水沉积物中获取了总共106个碎屑磷灰石（U - Th）/He（AHe）和100个磷灰石裂变径迹（AFT）单颗粒年龄，其流域海拔在530米到3960米之间。这些数据与从一个约2400米垂直剖面上采集的9个AHe和9个AFT基岩年龄相结合，以检验流域内侵蚀是均匀分布还是非均匀分布的假设。采用蒙特卡罗抽样模型和柯伊伯统计检验来量化冰水沉积物来源的海拔范围。AHe数据的模型结果表明流域内侵蚀近乎均匀，沉积物更倾向于来源于海拔约2900米到2700米的区域。年龄数据显示，最大的沉积物来源靠近现今的平衡线高度（ELA）。这些结果证明了AHe碎屑热年代学（在较小程度上AFT数据也是如此）在量化单个地貌过程侵蚀分布方面的实用性，以及该技术的一些局限性。
Understanding the spatial distribution of glacial catchment erosion during glaciation has previously proven difficult due to limited access to the glacier bed. Recent advances in detrital thermochronology provide a new technique to quantify the source elevation of sediment. This approach utilizes the tendency of thermochronometer cooling ages to increase with elevation and provides a sediment tracer for the elevation of erosion. We apply this technique to the Tiedeman Glacier in the heavily glaciated Mount Waddington region, British Columbia. A total of 106 detrital apatite (U-Th)/He (AHe) and 100 apatite fission track (AFT) single-grain ages was presented from the modern outwash of the Tiedemann Glacier with catchment elevations between 530 and 3960m. These data are combined with nine AHe and nine AFT bedrock ages collected from a similar to 2400m vertical transect to test the hypotheses that erosion is uniformly or nonuniformly distributed in the catchment. A Monte Carlo sampling model and Kuiper statistical test are used to quantify the elevation range where outwash sediment is sourced. Model results from the AHe data suggest nearly uniform erosion in the catchment, with a preference for sediment being sourced from similar to 2900 to 2700m elevation. Ages indicated that the largest source of sediment is near the present-day ELA. These results demonstrate the utility of AHe detrital thermochronology (and to a lesser degree AFT data) to quantify the distribution of erosion by individual geomorphic processes, as well as some of the limitations of the technique.