Abstract Overdeepenings (ODs) are erosional features that have been excavated below the regional sea/fluvial base level to produce closed topographic basins. Accessing bedrock topography and OD volume is often challenging. Hence, despite constituting major landscape features and being widespread in (paleo-)glaciated regions, ODs have been overlooked and the subglacial processes involved in their evolution have remained debated. In the Swiss Alpine foreland and valleys, ODs are commonly found filled with water or large volumes of sediment. Using a GIS-Matlab approach based on topographic datasets and bedrock contour-curves, we mapped the spatial distribution of ODs in Switzerland and adjacent areas in the ice-free Alpine areas. The majority of the mapped ODs occurs in very-low bedrock erosional resistance, where ODs are larger, wider and shallower than in medium to high bedrock erosional resistance domains, evidencing a strong lithological control on OD geometry. Longitudinal asymmetry and hypsometric integral suggest a dominance of quarrying during OD evolution and, for selected glacial catchments, headward erosion propagation or high sediment evacuation efficiency. OD surface data (surface and length) can be tentatively used for extracting OD subsurface metrics (depths, nested valleys and first-order volume estimates). Our data seem to indicate that ODs may initiate as multiple small nested valleys and progress to a single and connected depression. Transversal cross-sections also suggest a negative feedback between the erosion potential for deep carving and the presence of low-resistance bedrock, where subglacial meltwater infiltration could have played a key role in OD evolution. Although insightful relationships have been evidenced for ODs in the Swiss Alps and foreland, we have also observed a high spatial variability in key OD metrics such as surface area and depth. This results in general (first-order) interpretations at regional scale, but currently prevent to quantitatively constrain physical subglacial processes at their origin. Comparisons with existing OD datasets under present-day ice (Greenland, Antarctica and modern Swiss glaciers) place our results in a broader context and allow a step forward in our understanding of the complex patterns and mechanisms of (sub-)glacial erosion and resulting landforms.

中文翻译：

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瑞士阿尔卑斯山和前陆的冰川过度加深：空间分布和形态测量学

摘要 Overdeepenings (ODs) 是在区域海/河流基线以下被挖掘以产生封闭地形盆地的侵蚀特征。访问基岩地形和 OD 体积通常具有挑战性。因此，尽管构成了主要的景观特征并在（古）冰川地区广泛存在，但 OD 却被忽视了，并且其演化所涉及的冰下过程仍然存在争议。在瑞士高山前陆和山谷中，通常发现 OD 充满水或大量沉积物。使用基于地形数据集和基岩等高线曲线的 GIS-Matlab 方法，我们绘制了瑞士和无冰阿尔卑斯地区相邻地区 OD 的空间分布图。大多数映射的 OD 发生在非常低​​的基岩侵蚀阻力中，其中 OD 较大，比中高基岩抗侵蚀域更宽更浅，证明了对 OD 几何形状的强烈岩性控制。纵向不对称和测压积分表明在 OD 演化过程中采石占主导地位，对于选定的冰川集水区，向前侵蚀传播或沉积物排出效率高。OD 表面数据（表面和长度）可暂时用于提取 OD 地下指标（深度、嵌套山谷和一阶体积估计）。我们的数据似乎表明 OD 可能以多个小的嵌套山谷开始，并发展为一个单一且相连的洼地。横向横截面也表明深雕刻的侵蚀潜力与低阻力基岩的存在之间存在负反馈，冰下融水渗入可能在 OD 演化中发挥了关键作用。尽管已证明瑞士阿尔卑斯山和前陆的 OD 具有深刻的关系，但我们也观察到关键 OD 指标（例如表面积和深度）的空间变异性很高。这导致区域尺度上的一般（一阶）解释，但目前阻止在其起源处定量限制物理冰下过程。与当今冰层（格陵兰、南极洲和现代瑞士冰川）下现有 OD 数据集的比较将我们的结果置于更广泛的背景下，并使我们对（亚）冰川侵蚀和由此产生的地貌的复杂模式和机制的理解向前迈进了一步. 我们还观察到关键 OD 指标（例如表面积和深度）的高空间变异性。这导致区域尺度上的一般（一阶）解释，但目前阻止在其起源处定量限制物理冰下过程。与当今冰层（格陵兰、南极洲和现代瑞士冰川）下现有 OD 数据集的比较将我们的结果置于更广泛的背景下，并使我们对（亚）冰川侵蚀和由此产生的地貌的复杂模式和机制的理解向前迈进了一步. 我们还观察到关键 OD 指标（例如表面积和深度）的高空间变异性。这导致区域尺度上的一般（一阶）解释，但目前阻止在其起源处定量限制物理冰下过程。与当今冰层（格陵兰、南极洲和现代瑞士冰川）下现有 OD 数据集的比较将我们的结果置于更广泛的背景下，并使我们对（亚）冰川侵蚀和由此产生的地貌的复杂模式和机制的理解向前迈进了一步.