Constraining landscape history and glacial erosivity using paired cosmogenic nuclides in Upernavik, northwest Greenland
Constraining landscape history and glacial erosivity using paired cosmogenic nuclides in Upernavik, northwest Greenland
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使用格陵兰岛西北部乌佩纳维克的成对宇宙成因核素限制景观历史和冰川侵蚀力
DOI：
10.1130/b30813.1
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发表时间：
2013
影响因子：
4.9
通讯作者：
D. Rood
中科院分区：
文献类型：
--
作者：
L. Corbett;P. Bierman;J. Graly;T. Neumann;D. Rood
高纬度的景观演变过程有可能保存旧的，残留的表面，通过埋葬冷基，非侵蚀性冰川冰。为了调查高北极地区的景观历史和年龄，我们分析了格陵兰西北部乌佩尔纳维克33块岩石中的宇宙成因10 Be和26 Al。我们采样相邻的岩石巨石对沿着100公里的样带海拔高达1000米以上。基岩样品显着老的表观暴露年龄比相应的巨石样品，最低限制年龄随海拔升高。对33个样品中的20个进行的双同位素计算（26 Al/ 10 Be）得出的最小极限暴露持续时间高达112 k. y，最小极限埋藏时间可达900 k.y.，最小极限总历史可达990 k. y。10 Be和26 Al的患病率继承自以前的暴露时期，特别是在高海拔的基岩样品，表明这些地区记录长期和复杂的表面暴露的历史，包括显着的埋藏期，几乎没有冰下侵蚀。长期的总历史表明，这些高海拔的表面大部分保存在寒冷的，非侵蚀性的冰或雪原下，至少在第四纪的后半期。由于高浓度的遗传核素，只有六个最年轻的巨石样本似乎记录了冰退缩的时间。这6个样品表明乌佩尔纳维克海岸在11.3 ± 0.5 ka（平均值± 1标准差）的冰川消退。沿着100 km的样带，冰消年龄沿着没有差异，这表明冰缘位置以每年1.20亿的速度迅速消退。
High-latitude landscape evolution processes have the potential to preserve old, relict surfaces through burial by cold-based, nonerosive glacial ice. To investigate landscape history and age in the high Arctic, we analyzed in situ cosmogenic 10 Be and 26 Al in 33 rocks from Upernavik, northwest Greenland. We sampled adjacent bedrock-boulder pairs along a 100 km transect at elevations up to 1000 m above sea level. Bedrock samples gave significantly older apparent exposure ages than corresponding boulder samples, and minimum limiting ages increased with elevation. Two-isotope calculations ( 26 Al/ 10 Be) on 20 of the 33 samples yielded minimum limiting exposure durations up to 112 k.y., minimum limiting burial durations up to 900 k.y., and minimum limiting total histories up to 990 k.y. The prevalence of 10 Be and 26 Al inherited from previous periods of exposure, especially in bedrock samples at high elevation, indicates that these areas record long and complex surface exposure histories, including significant periods of burial with little subglacial erosion. The long total histories suggest that these high-elevation surfaces were largely preserved beneath cold-based, nonerosive ice or snowfields for at least the latter half of the Quaternary. Because of high concentrations of inherited nuclides, only the six youngest boulder samples appear to record the timing of ice retreat. These six samples suggest deglaciation of the Upernavik coast at 11.3 ± 0.5 ka (average ± 1 standard deviation). There is no difference in deglaciation age along the 100 km sample transect, indicating that the ice-marginal position retreated rapidly at rates of ∼120 m yr −1 .