The Impact of Active Tectonics on the Geomorphological Evidence of Alluvial Fans (Case Study: Alluvial Fans between Bardaskan and Kashmar)

This study investigated the impact of active tectonics, specifically the Dorubeh fault and an oblique-slip reverse fault, on the morphology of alluvial fans situated between Kashmar City and Ali Abad Keshmar Village in Bardaskan. The research employed a cartographic-analytical approach, utilizing 1:25,000 topographical maps, 1:100,000 and 1:250,000 geological maps, Landsat satellite images, and Google Earth. Mapping and image processing were conducted using such software as ArcMap, ArcView, Google Earth, and QGIS. The results demonstrated that fault activity plays a crucial role in shaping the predominant geomorphic features within this region, specifically the formation of alluvial fans known as bajada. The oblique-slip reverse fault, specifically, has induced significant modifications in the alluvial fans. It has repositioned the primary channels from central to peripheral and lateral positions, leading to alterations in sediment deposition patterns. Consequently, certain alluvial fans now intersect at three transverse surfaces and two longitudinal and transverse surfaces. The Doruneh fault’s activity is characterized by the manifestation of uplifts, pressure ridges, and pressure anticlines occurring at various sections within the alluvial fans, including the upper, lower, and basal regions. This fault caused left-lateral offsets in certain sub-channels on the fan's surface, resulting in the development of single-surface and nested two-surface transverse and longitudinal alluvial fans at the base of the fan and the base of the pressure ridges. Furthermore, it modified the point of intersection of the primary alluvial channels, leading to the formation of segmented fans downstream of Doruneh fault.