Abstract The relationship between the spatial variability of soil elements, weathering and erosion rates can be very complex. Topography, abruptly-changing elevation gradients and slopes of varying geological composition exert an important influence on weathering trajectories and erosion. This complex interconnectivity is only rarely addressed in weathering studies. The main objectives of this investigation are, therefore, to relate weathering and erosion to various and geomorphic units in a dry-alpine and threshold landscape having steep slopes (Kan catchment, Tehran Province, Iran). A number of common weathering indices were tested using a genetic algorithm. The best indices are the (K + Na)/Ti ratio, the WIP (weathering index according to Parker), and the PI (product index according to Ruxton). However, the recently suggested 4Si-M+-R2 and M-F-Wmin systems discriminate weathering trends more accurately. Our results show that these soils have a low to moderate weathering stage. Weathering trajectories point to the active formation of kaolinite and oxyhydroxides. River sediments are slightly more weathered and contain the most-weathered topsoils and suggest erosion in the catchment is predominantly due to topsoil removal. Chemical weathering is influenced by the dominant geomorphic units (unconsolidated deposits of the Quaternary and solid bedrock) and landform features (combination of altitude and slope). Aspect does not appear to have a significant impact on weathering. Denudation (~erosion) rates were determined using meteoric 10Be since the fluvial sediments did not contain enough quartz for in situ 10Be analyses. This procedure has higher uncertainties due to difficulties in estimating the depositional flux of meteoric 10Be. Due to tectonic uplift, the erosion rates are very high. To maintain a soil layer, soil production rates must be also high. Although annual precipitation is relatively low, slope and soil dynamics seem particularly high, which leads to a fast turnover of the soil material and maintains the weathering intensity at a rather low to intermediate level.

中文翻译：

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将化学风化和侵蚀的空间变异性与地质和地形区联系起来

摘要 土壤元素的空间变异性、风化和侵蚀速率之间的关系可能非常复杂。地形、突然变化的海拔梯度和不同地质成分的坡度对风化轨迹和侵蚀产生重要影响。这种复杂的互连性在风化研究中很少涉及。因此，本次调查的主要目标是将风化和侵蚀与具有陡峭斜坡的干高山和阈值景观（伊朗德黑兰省坎集水区）中的各种地貌单元联系起来。使用遗传算法测试了许多常见的风化指数。最好的指数是 (K + Na)/Ti 比率、WIP（根据 Parker 的耐候指数）和 PI（根据 Ruxton 的产品指数）。然而，最近建议的 4Si-M+-R2 和 MF-Wmin 系统更准确地区分了风化趋势。我们的结果表明，这些土壤具有低到中度的风化阶段。风化轨迹表明高岭石和羟基氧化物的活跃形成。河流沉积物风化程度稍高，含有风化最严重的表层土，表明流域的侵蚀主要是由于表层土的去除。化学风化受主要地貌单元（第四纪的松散沉积和固体基岩）和地貌特征（海拔和坡度的组合）的影响。方面似乎对风化没有显着影响。由于河流沉积物中没有足够的石英进行原位 10Be 分析，因此使用大气 10Be 确定了剥蚀（~侵蚀）率。由于难以估计流星 10Be 的沉积通量，该程序具有较高的不确定性。由于构造抬升，侵蚀率非常高。为了保持土壤层，土壤生产率也必须很高。虽然年降水量相对较低，但坡度和土壤动力学似乎特别高，这导致土壤物质的快速周转并使风化强度保持在相当低到中等的水平。