Impact of glacial isostatic adjustment on cosmogenic surface-exposure dating
Impact of glacial isostatic adjustment on cosmogenic surface-exposure dating
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冰川等静力调整对宇宙生成物地表暴露年代测定的影响
DOI：
10.1016/j.quascirev.2019.03.012
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发表时间：
2019-05-15
影响因子：
4
通讯作者：
Dalton, A. S.
中科院分区：
文献类型：
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作者：
Jones, R. S.;Whitehouse, P. L.;Dalton, A. S.
计算宇宙起源核素表面暴露年龄在很大程度上取决于对样本地点海拔的了解。由于冰川均衡调整（GIA），海拔随着时间的推移而发生变化，可能会改变当地核素的产生率，从而改变表面暴露年龄。在这里，我们评估的影响，GIA的表面曝光测年计算全球时间依赖的生产率，因为末次冰期最大使用表面高程校正和未校正的GIA。我们发现，GIA效应的大小是空间和时间可变的。在最大的冰川均衡沉降期，在大冰块内部（北美、斯堪的纳维亚和南极洲西部），核素的产生可减少50%。尽管影响较小，但在冰盖边缘仍然很明显，那里的核素产量减少了>5%，可能> 10%，使这些地区的暴露年龄更大。远离冰盖边缘，陆地表面可以均衡地升高，这可以使核素产量增加5%以上，因此使照射年龄更年轻。最近暴露的区域或远离大冰块的区域通常受到的影响较小。重要的是，我们发现在主要Be-10生产校准地点的影响是
Calculating cosmogenic-nuclide surface-exposure ages is critically dependent on a knowledge of the altitude of the sample site. Changes in altitude have occurred through time as a result of glacial isostatic adjustment (GIA), potentially altering local nuclide production rates and, therefore, surface-exposure ages. Here we assess the impact of GIA on surface-exposure dating by calculating global time-dependent production rates since the Last Glacial Maximum using surface elevations that were corrected and uncorrected for GIA. We find that the magnitude of the GIA effect is spatially and temporally variable. Nuclide production could be reduced by up to 50% in the interior of large ice masses (in North America, Scandinavia and West Antarctica) at times of maximum glacial isostatic depression. Although smaller, the effect is still significant at ice sheet margins, where nuclide production is reduced by >5% and potentially >10%, making exposure ages older in those areas. Away from the ice sheet margins, land surfaces can be isostatically elevated, which can increase nuclide production by >5% and, therefore, make exposure ages younger. Areas that were more recently exposed or that are distal to large ice masses will generally be less affected. Importantly, we find that the effect at the primary Be-10 production calibration sites is