Tectonic and surface processes (e.g., erosion) act in concert to denude and flatten elevated topography during and following collisional uplift. In orogens that collapsed rapidly (<10 Myr), the effectiveness and relative contribution of erosion remains poorly understood. Here, we use 1-D and 2-D finite-difference models to test plausible magnitudes of erosion during denudation of the Scandian orogenic wedge, in northern Scotland, which previous work suggests may have been very rapid. Thermochronologic, stratigraphic, and thermobarometric data constrain initial post-collision uplift rates as well as the cumulative post-collisional exhumation magnitude. Using these constraints, we consider an idealized orogen subjected to fluvial incision, hillslope diffusion, and subsequent isostatic compensation for a duration of 10 Myr. Using a range of geomorphic parameters, we evaluate whether erosion alone is sufficient to achieve the observed cumulative exhumation. Additionally, we apply a thermal model during the same period to determine the viability of the previous erosion estimates in the presence of a transient geothermal gradient. For most cases with initial uplift rates of 0.5–2.5 mm yr⁻¹, total erosion is insufficient to account for the observed Scandian denudation history, regardless of whether a fixed or transient geothermal gradient is assumed. Average elevations near the crest of the modeled orogen after 10 Myr are >1.4 km, which is inconsistent with the post-Scandian landscape relief interpreted from the reconstructed depositional surface of the Emsian (407–403 Ma) Old Red Sandstone, Collectively these findings imply a combination of rapid erosion and tectonic denudation likely accomplished the rapid collapse of the Scandian wedge.

中文翻译：

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快速造山剥蚀侵蚀地球动力学阈值的评价

在碰撞隆升期间和之后，构造和地表过程（例如，侵蚀）共同作用以剥蚀和平坦化升高的地形。在迅速崩塌（<10 Myr）的造山带中，侵蚀的有效性和相对贡献仍然知之甚少。在这里，我们使用一维和二维有限差分模型来测试在苏格兰北部斯堪的纳造山带剥蚀过程中可能发生的侵蚀程度，之前的工作表明这可能非常迅速。热年代学、地层学和热气压数据限制了初始碰撞后抬升率以及累积碰撞后剥落幅度。使用这些约束条件，我们考虑了一个理想化的造山带，在 10 Myr 的持续时间内经受了河流切割、山坡扩散和随后的均衡补偿。使用一系列地貌参数，我们评估仅侵蚀是否足以实现观察到的累积剥落。此外，我们在同一时期应用了一个热模型，以确定在存在瞬态地温梯度的情况下先前侵蚀估计的可行性。对于初始抬升率为 0.5-2.5 毫米/年的大多数情况^-1，总侵蚀不足以解释观察到的斯堪的纳剥蚀历史，无论假设是固定的还是瞬态的地温梯度。10 Myr 之后模拟造山带顶部附近的平均海拔 > 1.4 km，这与从 Emsian (407–403 Ma) 旧红砂岩的重建沉积表面解释的后斯堪的亚景观浮雕不一致，这些发现共同表明快速侵蚀和构造剥蚀的结合可能导致了斯堪的纳楔形体的快速坍塌。