Moraine chronosequence of the Donnelly Dome region, Alaska
Moraine chronosequence of the Donnelly Dome region, Alaska
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DOI：
10.1016/j.yqres.2010.04.007
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发表时间：
2010-07
影响因子：
2.3
通讯作者：
A. Matmon;J. Briner;G. Carver;P. Bierman;R. Finkel
中科院分区：
文献类型：
--
作者：
A. Matmon;J. Briner;G. Carver;P. Bierman;R. Finkel
我们给出了北阿拉斯加山脉更新世冰川作用的参考地--三角洲河谷冰川的10Be暴露年龄。年龄来自三角洲冰期和唐纳利冰期沉积的物质，分别与MIS6和MIS2相关联。10Be年代学表明，在MIS4/3期间，至少有部分三角洲冰川稳定，唐纳利冰川稳定了∼17ka。这些年龄与阿拉斯加山脉和阿拉斯加其他地区的其他日期相关联，表明整个贝林吉亚在晚更新世冰川脉动期间是同步的。从巨石周围和没有巨石的表面收集了几种样品类型：巨石、单一碎屑和砾石样品(混合的小碎屑)。对这些样品的10Be年龄进行对比，揭示了前/后沉积过程的影响，包括巨石侵蚀、巨石折返和冰雹表面下降。这些过程持续发生，但似乎在连续的冰期期间和之后加速。结果是一个多峰年龄分布，表明一旦冰川持续到后来的冰川，从该冰川上采集的样品得出的宇宙成因年龄的年代学意义显着减弱。全新世年龄的缺失意味着12ka以来相对较小的折返和/或风化作用。
We present 10Be exposure ages from moraines in the Delta River Valley, a reference locality for Pleistocene glaciation in the northern Alaska Range. The ages are from material deposited during the Delta and Donnelly glaciations, which have been correlated with MIS 6 and 2, respectively. 10Be chronology indicates that at least part of the Delta moraine stabilized during MIS 4/3, and that the Donnelly moraine stabilized ∼ 17 ka. These ages correlate with other dates from the Alaska Range and other regions in Alaska, suggesting synchronicity across Beringia during pulses of late Pleistocene glaciation. Several sample types were collected: boulders, single clasts, and gravel samples (amalgamated small clasts) from around boulders as well as from surfaces devoid of boulders. Comparing 10Be ages of these sample types reveals the influence of pre/post-depositional processes, including boulder erosion, boulder exhumation, and moraine surface lowering. These processes occur continuously but seem to accelerate during and immediately after successive glacial episodes. The result is a multi-peak age distribution indicating that once a moraine persists through subsequent glaciations the chronological significance of cosmogenic ages derived from samples collected on that moraine diminishes significantly. The absence of Holocene ages implies relatively minor exhumation and/or weathering since 12 ka.