Understanding the influence of bedrock lithology on the catchment-averaged erosion rates of normal fault-bounded catchments and the effect that different bedrock erodibilties have on the evolution of transient fluvial geomorphology remain major challenges. To investigate this problem, we collected 18 samples for ¹⁰Be and ²⁶Al cosmogenic nuclide analysis to determine catchment-averaged erosion rates along the well-constrained Gediz Fault system in western Türkiye, which is experiencing fault-driven river incision owing to a linkage event ~0.8 Ma and has weak rocks overlying strong rocks in the footwall. Combined with existing cosmogenic data, we show that the background rate of erosion of the pre-incision landscape can be constrained as <92 mMyr⁻¹, and erosion rates within the transient reach vary from 16 to 1330 mMyr⁻¹. Erosion rates weakly scale with unit stream power, steepness index and slip rate on the bounding fault, although erosion rates are an order of magnitude lower than slip rates. However, there are no clear relationships between erosion rate and relief or catchment slope. Bedrock strength is assessed using Schmidt hammer rebound and Selby Rock Mass Strength Assessments; despite a 30-fold difference in erodibility, there is no difference in the erosion rate between strong and weak rocks. We argue that, for the Gediz Graben, the strong lithological contrast affects the ability of the river to erode the bed, resulting in a complex erosional response to uplift along the graben boundary fault. Weak covariant trends between erosion rates and various topographic factors potentially result from incomplete sediment mixing or pre-existing topographic inheritance. These findings indicate that the erosional response to uplift along an active normal fault is a complex response to multiple drivers that vary spatially and temporally.

中文翻译：

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10Be 和 26Al 宇宙成因核素分析揭示了穿越活动正断层的瞬态河流系统对隆起和岩石强度对比的复杂侵蚀响应

了解基岩岩性对正常断层流域流域平均侵蚀率的影响以及不同基岩侵蚀对瞬态河流地貌演化的影响仍然是主要挑战。为了研究这个问题，我们收集了 18 个样本进行¹⁰ Be 和²⁶ Al 宇宙成因核素分析，以确定土耳其西部良好约束的盖迪兹断层系统沿线的流域平均侵蚀率，由于连锁事件，该断层系统正在经历断层驱动的河流切割~0.8 Ma，下盘有弱岩石覆盖强岩石。结合现有的宇宙成因数据，我们表明，切割前景观的背景侵蚀率可以限制为<92 mMyr ^-1，瞬时范围内的侵蚀率从16到1330 mMyr ^-1不等。尽管侵蚀率比滑动率低一个数量级，但侵蚀率与边界断层上的单位水流功率、陡度指数和滑动率的关系微弱。然而，侵蚀率与地形或流域坡度之间没有明确的关系。使用施密特锤回弹和塞尔比岩体强度评估来评估基岩强度；尽管侵蚀性相差30倍，但强岩石和弱岩石的侵蚀率没有差异。我们认为，对于盖迪兹地堑来说，强烈的岩性对比影响了河流侵蚀河床的能力，导致对沿地堑边界断层的隆起产生复杂的侵蚀反应。侵蚀率和各种地形因素之间的弱协变趋势可能是由于不完全的沉积物混合或预先存在的地形继承造成的。这些发现表明，沿活动正断层对隆起的侵蚀响应是对空间和时间上变化的多个驱动因素的复杂响应。