Climatic controls on debris‐flow activity and sediment aggradation: The Del Medio fan, NW Argentina
Climatic controls on debris‐flow activity and sediment aggradation: The Del Medio fan, NW Argentina
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对泥石流活动和沉积物堆积的气候控制：阿根廷西北部的德尔梅迪奥扇
DOI：
10.1002/2016jf003912
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发表时间：
2016
期刊：
影响因子：
--
通讯作者：
Strecker
中科院分区：
文献类型：
--
作者：
Schildgen;Tofelde;Wittmann;Scherler;Alonso;Strecker
在中安第斯山脉，关于冲积阶地和山谷填充物的几项研究将沉积物淤积与沉积物供应增加的时期联系起来。然而，关于构造或气候因素在引发供应增加方面是否最重要的争论仍在继续。乌马瓦卡盆地（阿根廷西北部科迪勒拉东部）的德尔梅迪奥流域位于半湿润和干旱气候之间的过渡区，是该山间山谷中唯一活跃的泥石流扇。通过结合10Be分析的巨石和沉积物样品内的德尔梅迪奥集水区，与区域形态测量附近的集水区，我们确定负责在德尔梅迪奥风扇的沉积和他们可能的触发器的表面过程。我们发现，在过去的400年里，扇面已形成的泥石流和通道撕脱。在可能影响沉积的潜在构造、气候和自生因素中，我们的分析指出了几个驱动加积的有利因素的组合。特别是在降雨量相对较低和运输能力有限的地区，偶尔大量降雨对易发生破坏的岩石类型的陡坡的影响。这些特征主要与潮湿的前陆和干旱的造山带内部之间的气候过渡带有关，这造成了沉积物供应和沉积物转移之间的不平衡。今天在Del Medio流域驱动加积的条件和过程可能提供了一个现代的模拟驱动加积在其他附近的支流在过去的条件和过程。
In the Central Andes, several studies on alluvial terraces and valley fills have linked sediment aggradation to periods of enhanced sediment supply. However, debate continues over whether tectonic or climatic factors are most important in triggering the enhanced supply. The Del Medio catchment in the Humahuaca Basin (Eastern Cordillera, NW Argentina) is located within a transition zone between subhumid and arid climates and hosts the only active debris‐flow fan within this intermontane valley. By combining10Be analyses of boulder and sediment samples within the Del Medio catchment, with regional morphometric measurements of nearby catchments, we identify the surface processes responsible for aggradation in the Del Medio fan and their likely triggers. We find that the fan surface has been shaped by debris flows and channel avulsions during the last 400 years. Among potential tectonic, climatic, and autogenic factors that might influence deposition, our analyses point to a combination of several favorable factors that drive aggradation. These are in particular the impact of occasional abundant rainfall on steep slopes in rock types prone to failure, located in a region characterized by relatively low rainfall amounts and limited transport capacity. These characteristics are primarily associated with the climatic transition zone between the humid foreland and the arid orogen interior, which creates an imbalance between sediment supply and sediment transfer. The conditions and processes that drive aggradation in the Del Medio catchment today may provide a modern analog for the conditions and processes that drove aggradation in other nearby tributaries in the past.
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