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首页> 外文期刊>Earth Surface Processes and Landforms: The journal of the British Geomorphological Research Group >Catchment lithology as a major control on alluvial megafan development, Kohrud Mountain range, central Iran
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Catchment lithology as a major control on alluvial megafan development, Kohrud Mountain range, central Iran

机译：流域岩性作为对冲积巨扇发育的主要控制手段，伊朗中部科鲁德山脉

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摘要

The relative importance of tectonics, climate, base level and source lithology as primary factors on alluvial-fan evolution, fan morphology and sedimentary style remain in question. This study examines the role of catchment lithology on development and evolution of alluvial megafans (>30km in length), along the flanks of the Kohrud Mountain range, NE Esfahan, central Iran. These fans toe out at axial basin river and playa-fringe sediments towards the centre of basin and tectonics, climatic change and base-level fluctuations, were consistent for their development. They formed in a tectonically active basin, under arid to semiarid climate and a long term (Plio-Pleistocene to Recent) change from wetter to drier conditions. The key differences between two of these fans, Soh and Zefreh fans, along the west and south flanks of this mountain range, is that their catchments are underlain by dissimilar bedrock types. The source-area lithologies of the Soh and Zefreh fans are in sedimentary and igneous terrains, respectively, and these fans developed their geometry mainly in response to different weathering intensities of their catchment bedrock lithologies. Fan surface mapping (based on 1/50000 topographic maps, satellite images, and fieldwork), reveals that the geomorphic evolution of these fans differs in that the relatively large-scale incision and through trenching of the Soh fan is absent in the Zefreh fan. Whereas the limited sediment supply of the Soh fan has resulted in a deep incised channel, the Zefreh fan has remained aggradational with little or no trenching into proximal to medial fan surface due to its catchment bedrock geology, composed mainly by physically weathered volcaniclastic lithology and characterized by high sediment supply for delivery during episodic flash floods. Sediment supply, which is mainly a function of climate and source lithology, is a dominant driver behind the development of fan sequences in alluvial megafans.
机译：构造，气候，基础水平和源岩性作为冲积扇演化，扇形和沉积样式的主要因素的相对重要性仍然存在疑问。这项研究考察了伊朗中部NE Esfahan的Kohrud山脉两侧的集水岩性对冲积巨扇（长度大于30 km）的发育和演化的作用。这些风扇在盆地轴向河涌出，并向盆地中心和滩涂边缘沉积物，构造，气候变化和基准面波动与它们的发育一致。它们形成于一个构造活跃的盆地，处于干旱至半干旱气候下，长期（从上新世到近新世）从潮湿到干燥的变化。 Soh和Zefreh风扇这两个风扇之间的主要区别是，在该山脉的西侧和南侧，其集水区位于不同的基岩类型之下。 Soh和Zefreh扇的源区岩性分别处于沉积和火成区，这些扇主要根据其集水基岩岩性的不同风化强度发展了其几何形状。风扇表面贴图（基于1/50000地形图，卫星图像和野外作业）显示，这些风扇的地貌演化不同，因为Zefreh风扇中没有较大尺寸的切口和Soh风扇的开槽。 Soh风机有限的沉积物供应导致了一条深切的通道，而Zefreh风机由于其集水基岩地质学（主要由物理风化的火山碎屑岩岩性组成）而保持凝结状态，几乎没有或几乎没有向内侧风机表面开槽。大量的泥沙供应，以便在突发性山洪暴发期间输送。沉积物供应主要是气候和烃源岩性的函数，是冲积巨型扇形扇序列发展的主要驱动力。

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