Differential Features of Alluvial Fans Controlled by Quaternary Tectonic Activities around Misho-Dagh Mountainous Area (Northwest of Iran)

The northern and southern borders of Mishow- Dagh mountainous chain (northwest of Iran) include zones with ideal characteristics for optimum development of alluvial fans. The alluvial fan development in this area is related to environmental factors such as tectonic activities. In this study, we discussed to what extent tectonics affect the peculiarities in the sedimentary processes occurring in the fans on different sections of the study area (37 Quaternary alluvial fans in four groups), thus causing geomorphological anomalies in them. For this object, we analyzed the main morphological features of the fans and their drainage basins, as well as some of their constitutive elements. We then focused on the connection zone between the fans and their drainage basins. Finally, we analyzed the possible relations between the different parameters of the drainage areas and the fans. All of these analysis were based on interpretation of geological, topographical, areal photos and satellite images and as well as field studies. The results showed that tectonics play a double role; On the one hand, there have been recent displacements in the zone occupied by the drainage areas, as well as between the basement and the basins in which the fans accumulate and, on the other hand, tectonic activity is responsible for the more intense subsidences in the northern and southern plains of the study area, which gives rise to significant differences in the rate of creation of accommodation space between some sectors and others. Generally, Quaternary tectonic activities have caused changes in sweep angle, longitudinal and fan cross profiles, segmentation, head incision, development of erosional gullies, uplift of Quaternary sediments, formation of telescopic alluvial fans, structure of fans and elongation of drainage basins, slope changes on mountain fronts, positive allometry in fan areas and drainage basin relations, and development of new sedimentary basins.