Abstract The pattern of cosmogenic nuclide inheritance within bedrock surfaces in previously glaciated regions can be used to assess the efficiency of glacial erosion and constrain topographic evolution. Here, we present fifty new in-situ cosmogenic 10Be and 26Al pairs in bedrock and boulder erratics from South Greenland. The data demonstrate rapid retreat of the South Greenland Ice Sheet in the early Holocene and a clear gradient in cosmogenic nuclide inheritance in bedrock with elevation. Sites 800 m above sea level (m a.s.l.) generally show limited or no nuclide inheritance (exposure from before the last glaciation). In contrast, the nuclide inheritance in samples from sites at higher elevations varies from negligible to > 90 kyr of exposure before the last glaciation, depending on the topographic setting. Our results suggest that steering of ice into troughs led to substantial erosion ( > 2.6 m ) in the troughs over the last glacial cycle, even at elevations above 1500 m a.s.l., while bedrock on summit flats at similar elevations experienced much less erosion. Inverse Markov-Chain Monte Carlo (MCMC) modelling of the nuclide inventories further indicates that selective linear erosion developed > 1 Myr ago at the summit flat closest to the present ice margin, and effectively limited the subsequent erosion to 2.6 m . Erosion of the Redekammen Ridge some 40 km from the present ice margin was slightly more efficient over the last 1 Myr, indicating that selective linear erosion is less pronounced, or developed later, here than at the summit flats. Long-term ice-cover histories are generally less well-constrained than the erosion histories. The results suggest that the summit flats were possibly ice-covered during large parts of the last 1 Myr and experienced minimal erosion during this interval, but it is also possible that they were only covered by ice during the coldest parts of the glacial periods and that a cover of regolith or overlying rock was stripped off during one of the latest major glaciations. Although inverse modelling cannot distinguish between these scenarios, we identify the more likely ice-cover scenarios for each site based on the geological setting and surface characteristics.

中文翻译：

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成对 26Al/10Be 核素约束下格陵兰南部的地形演化和冰川历史

摘要 先前冰川区基岩表面的宇宙成因核素遗传模式可用于评估冰川侵蚀的效率并限制地形演化。在这里，我们展示了 50 对新的原位宇宙成因 10Be 和 26Al 对，位于南格陵兰岛的基岩和巨石不规则处。数据表明，在全新世早期南格陵兰冰盖迅速退缩，基岩中宇宙成因核素遗传的明显梯度随海拔升高。海拔 800 m (m asl) 的地点通常显示有限或没有核素遗传（从最后一次冰期之前的暴露）。相比之下，来自较高海拔地点的样本中的核素遗传在最后一次冰川作用之前从可忽略不计到 > 90 kyr 不等，具体取决于地形设置。我们的结果表明，在最后一个冰期循环中，冰转向槽导致了槽中的大量侵蚀（> 2.6 m），即使海拔高于 1500 m asl，而类似海拔的山顶平坦上的基岩遭受的侵蚀要少得多。核素清单的逆马尔可夫链蒙特卡罗 (MCMC) 模型进一步表明，在最接近当前冰缘的山顶平坦处发生了 > 1 Myr 之前的选择性线性侵蚀，并有效地将随后的侵蚀限制在 2.6 m 。距离当前冰缘约 40 公里的 Redekammen Ridge 的侵蚀在过去 1 Myr 中的效率略高，这表明选择性线性侵蚀在这里比在山顶平坦处不那么明显或发展得更晚。与侵蚀历史相比，长期的冰盖历史通常受到较少的约束。结果表明，在过去 1 Myr 的大部分时间里，山顶的平坦地区可能被冰覆盖，并且在此期间经历了最小的侵蚀，但也有可能它们只在冰河时期最冷的部分被冰覆盖，并且在最近的一次主要冰川作用期间，风化层或上覆岩石的覆盖层被剥落。尽管逆向建模无法区分这些情景，但我们根据地质环境和地表特征为每个站点确定了更可能的冰盖情景。但也有可能它们只是在冰期最冷的时期被冰覆盖，而在最近的一次主要冰川期中，风化层或上覆的岩石被剥落。尽管逆向建模无法区分这些情景，但我们根据地质环境和地表特征为每个站点确定了更可能的冰盖情景。但也有可能它们只是在冰期最冷的时期被冰覆盖，而在最近的一次主要冰川期中，风化层或上覆的岩石被剥落。尽管逆向建模无法区分这些情景，但我们根据地质环境和地表特征为每个站点确定了更可能的冰盖情景。