نوع مقاله : مقاله پژوهشی
1 دانشجوی کارشناسی ارشد تکتونیک، دانشگاه خوارزمی تهران.
2 استادیار دانشکده علوم زمین، دانشگاه خوارزمی تهران.
3 استادیار دانشکده علوم پایه، دانشگاه آزاد واحد لاهیجان.
عنوان مقاله [English]
Morphotectonics is a knowledge that can determine the effect of active tectonic with using the geomorphic indices as a quantitative description of the Rivers form. The main objective of the morphotectonics is to extract the information on the rate and patterns of active deformation directly from the landscape topography. In the active areas of the land, the bedrock channel network has important connections between the length, height and pattern of the clay-shaped network of rocks, and; accordingly, quantitative measurements provide conditions that allow them to identify the status of active tectonics areas. The location of Iran in the Alpine-Himalayan folded belt has caused the most parts of Iran to be active in terms of tectonics; the Alborz orogenic belt is a part of the named area, and the placement of the studied area in the central Alborz has caused the area to be affected by this tectonic movements. This mountain range is the result of two orogenic movements, one of them is Precambrian ores (Acinitic), the course of which is essentially a metamorphism that leads to the interconnection and hardening of the paving stones in the Precambrian, The second one is the Alpine orogeny movements that it happens in Mesozoic and Cenozoic periods. This mountain range is approximately 600 kilometers long and 100 kilometers wide along the south side of the Caspian Sea. The northern margin of the Alborz line is usually sloping. General trend of study area is NE-SW. main faults of this study area is Khazar, North Great Alborz and Taleqan faults; which the Khazar fault is located on a structural boundary on the southern end of the Caspian Sea from Gorgan to Tonekabon cities and has a length of more than 600 kilometers. The north Alborz fault is a inverted-thrust fault and the general trend of this fault is parallel to the Khazar fault. Taleghan fault with approximate east-west orientation and approximate length of 64 km and has a slope to the south is located near Taleqan city in the central part of Alborz. According to the definition of “fault segments” which means the fragmentation of a fault along the length into smaller pieces due to the collision of other faults to it, the topographic changes or bending of the fault, can change the type of tectonic activity of this piece of the ratio fault To other parts. Therefore, studying the segments of large faults that located in the study area is important. In this research, the effect of active tectonic on the longitudinal profile of the river has been researched and studied with using of modern methods. Longitudinal profile was then obtained by using digital elevation method (DEM) in MATLAB and Arc GIS software environment and then the values of Ksn and θ indexes in central Alborz region between Chalous, Ramsar and Taleqan cities along each river were calculated and determine their relationship with the structures of the area. The rivers of the studied area were classified into 4 levels very high, high, medium and low according to the values of the Ksn. The results of this classification shows that the studied area has very high and high tectonic activity. Thus, The western part of the Caspian Sea with the Ksn index range of 298 and the western part of central Alborz in the Taleghan area with with the Ksn index range of 109 have the highest and lowest tectonic activity of the studied basin. After studying the effect of main areas fault such as Khazar fault, Great Alborz fault, Taleqan thrust it was determined that the recent tectonic activity due to the movements of these faults has been affected the rivers of the study area. Regarding the classification of the Ksn along named faults in the study area and the high values obtained, it was revealed that recent tectonic activity in this part of northern Iran was attributed not only by the activity of large faults such as Khazar and Alborz; but also from activity of Other minor faults, such as Azarak faults, south of Shirax village, Dezben, SiahBishe and Holoudaran village fault have caused changes in the rivers of the study area due to their movement and displacement.So that, Generally at the intersection of faults and rivers, longitudinal profiles undergo significant changes in gradients by activity of the named faults. Also, evidence of earthquakes and the geospatial evidence obtained from field observations such as the existence of deep and narrow gorges, alluvial terraces and Waterfalls is a proof of the results of this study.