Robl J, Heberer B, Prasicek G, Neubauer F, Hergarten S
Department of Geography and Geology University of Salzburg Salzburg Austria.
Institute of Earth and Environmental Sciences-Geology University of Freiburg Freiburg im Breisgau Germany.
J Geophys Res Earth Surf. 2017 Jan;122(1):310-334. doi: 10.1002/2016JF003884. Epub 2017 Jan 24.
The topography of the eastern Southern Alps (ESA) reflects indenter tectonics causing crustal shortening, surface uplift, and erosional response. Fluvial drainages were perturbed by Pleistocene glaciations that locally excavated alpine valleys. The Late Miocene desiccation of the Mediterranean Sea and the uplift of the northern Molasse Basin led to significant base level changes in the far field of the ESA and the Eastern Alps (EA), respectively. Among this multitude of mechanisms, the processes that dominate the current topographic evolution of the ESA and the ESA-EA drainage divide have not been identified. We demonstrate the expected topographic effects of each mechanism in a one-dimensional model and compare them with observed channel metrics. We find that the normalized steepness index increases with uplift rate and declines from the indenter tip in the northwest to the foreland basin in the southeast. The number and amplitude of knickpoints and the distortion in longitudinal channel profiles similarly decrease toward the east. Changes in slope of -transformed channel profiles coincide spatially with the Valsugana-Fella fault linking crustal stacking and uplift induced by indenter tectonics with topographic evolution. Gradients in across the ESA-EA drainage divide imply an ongoing, north directed shift of the Danube-ESA watershed that is most likely driven by a base level rise in the northern Molasse basin. We conclude that the regional uplift pattern controls the geometry of ESA-EA channels, while base level changes in the far field control the overall architecture of the orogen by drainage divide migration.
东阿尔卑斯山南部（ESA）的地形反映了导致地壳缩短、地表隆升和侵蚀响应的压入构造。河流排水系统受到更新世冰川作用的扰动，这些冰川在局部地区挖掘出高山峡谷。地中海晚中新世的干涸以及北磨拉石盆地的隆升，分别导致了ESA远场和东阿尔卑斯山（EA）远场的显著基准面变化。在众多这些机制中，主导ESA当前地形演化以及ESA-EA分水岭的过程尚未确定。我们在一维模型中展示了每种机制预期的地形效应，并将其与观测到的河道指标进行比较。我们发现，归一化陡度指数随隆升速率增加，并且从西北的压入尖端向东南的前陆盆地递减。裂点的数量和幅度以及纵向河道剖面的变形同样向东减小。-变换后的河道剖面坡度变化在空间上与瓦尔苏加纳-费拉断层重合，该断层将由压入构造引起的地壳堆积和隆升与地形演化联系起来。ESA-EA分水岭上的梯度意味着多瑙河-ESA流域正在向北发生位移，这很可能是由北磨拉石盆地的基准面上升驱动的。我们得出结论，区域隆升模式控制着ESA-EA河道的几何形态，而远场的基准面变化则通过分水岭迁移控制着造山带的整体结构。
