The Study of Neotectonic using Geomorphologic Indices and Evidences: A Case Study of Karganrood Talesh Watershed in West Guilan Province

Document Type : Research Article

Author

• Raf’at Shahmari Ardejani

Islamic Azad University, Astara Branch

10.22067/geo.v8i3.83055

Abstract

 

Introduction

Generally less space can be found on the surface of the Earth that is not constantly evolving, so Earth is has a dynamic system as one of its features. In fact, it can be said that active neoconstruction is deforming the surface of the earth. Geomorphological indices represent a useful tool for understanding the functionality and degree of dynamics of these processes. In order to achieve the objectives of the study, seven geomorphologic indices indicate that Korganrud basin is the most active tectonic evidence in the south of the basin in terms of active tectonic deformation. The purpose of preparing geomorphologic maps is recording information about the forms of surface, materials (soils and rocks), surface processes, and, in some cases, the age of land on these maps. The most successful approach to prepare such maps is the combination of field studies with the aerial photographs (Hosseinzadeh, 2007). The first geomorphologic map of Iran, in a scale of 1:2500000, is among a set of maps of the near East in the University of Tubingen in Germany in 1990, which was produced and released by Servati, in collaboration with Bausch and Grounret. Of course, some maps have been prepared by some colleagues of Tehran University, with the scale of 1:250000 and 1:50000. (Jedari Eivazi & Mahmoudi, 1991).

Materials and Methods

The research method was based on the analysis of form and process, library data, topographic maps, geological maps, and radar imagery as well as several field survey items. This paper presents eight geomorphological indices of Mountain Frontal Sinusitis (Smf), Drainage Basin Asymmetry (AF), valley floor to Valley Height Ratio (VF), Basin Shape (Bs), Transverse Topography (T), Hipsometric Curve (Hc), maze (S) and longitudinal river (SL) have been used to determine the new tectonic status of Karganud Talesh watershed. This study is a descriptive-analytical study which, based on the purpose, can be functional. Overall, the research process is as follows: the readiness and interest, experience and knowledge about the area, collecting large-scale topographic maps (1:25000) as the base maps, field visits and the observation of objects and phenomena on earth, drawing and producing primary map of land forms, geology and slope maps, analyzing data, aerial and satellite image analysis, and, finally, the analysis of results and producing the final geomorphologic map. Topographic map of 1:25000 and 1:50000, Guilan Faults’ Map 1:250000, Geological map of Rasht-Qazvin 1:100000, Geological map of Ardebil province 1:100000, satellite images of the west of Guilan 1:100000, and Aerial photos of the West of Guilan 1:20000 from the organization of Geological Survey of Iran (published in 1994).

Results and Discussion

The results show that Korganrood watershed is one of the mountainous watersheds in northwest of Gilan province and Talesh city. The passage of the Astara-Talesh National Fault about 400 km downstream of the eastern slopes overlooking the Gilan Plain, the Neur Fault near Khalras, and the folds indicate neotectonic activity and the occurrence of important tectonic phenomena in the area. The study area is in the West of Guilan province which starts from the zero point of the border between Iran and Azerbaijan (the town of Astara) and includes the southern parts of Astara city, Talesh, Rezvanshahr, and Masal. It is located between 38 ° 15 ´00 ˝to 38 ° 27 ´00 ˝north latitude of the equator and 48 ° 35 ´00˝ to 49 ° 14 ´00.˝east longitude (topographic map 1:25000) and has 3839/6 square kilometers. This includes about 26/1 % of the total area of Guilan province. The minimum height of the area is 28 meters in Astara coast, and a maximum altitude is about 3197 meters in Baghrouda Castle. The area under study is composed of four distinct morphology sections including: Beaches, Plains, Foothills and Mountains….

Conclusion

A direct mountain front indicates active faulting whereas the mountainous bent front shows weak tectonic activity and erosion superiority at altitudes. In this regard, the study area through the Astara-Talesh Fault Pass downstream of the basin as well as the Neur Fault upstream, are in themselves part of the northwestern Gilan tectonic zone. Because geomorphological indices are very important in assessing tectonic activity, they can easily identify areas that have experienced rapid or slow tectonic activity in the past. In this regard, of the geomorphological indices used in this study, only one confirms the inactivity of the basin and the rest all emphasize on the basin's inactivity.
Mountainous Areas: An average altitude of 1500 meters above the sea level, steep slopes, deep valleys, different streams on the slopes, existence of fault cliffs across the highlands of Talesh, and other issues can be some of the restrictive geomorphologic factors in the development of settlements in the area of the study. Geomorphologic map of the mountainous area shows that the distribution of settlements of Aq Masjid (White Mosque), Baskem Chal, Chamlar, Haji Amir, Vonabin, Heiran, Degarmankshi, Damiroughlikesh, Giladeh, Mashand, Dash Dibi, Baharestan, Latoun is influenced by the geomorphology (shape of the land). The things which are clearly visible in most areas are lack of flat land for the development and expansion of settlements.
Foothill areas have lower elevation than the surrounding mountainous areas, but compared to the plain areas have higher elevation of 100 to 500 meters with a relatively gentle slope, which extends a distance from mountains and connects to the plain. The main geomorphic elements of foothills region can be alluvial fan, concave and convex slopes, valleys and streams, cliffs, and the water path. Physical expansion of settlements usually encounters an obstacle while developing from one side. At the top of plains, the existence of mountain, high steep, rocks and boulder debris, and overall, sediments are the major obstacles for spatial development.
Plain Regions: The plains have higher rank than other units regarding the expansion and the number of urban and rural settlements. Spatial distribution of these kinds of settlements is more regular compared to the mountainous areas, but less regular compared to the foothill ones. The most important cities in the study area, such as Astara, Lavandavil, Choubar, and Haviq are formed in plain units. From among the most important effects of geomorphology in plains of the study area Kanroud, Lavandavil, Cholvand, Choubar, and Haviq rives can be mentioned. As most of these rivers pass through the city, they have left some traces in cities, some of which are river signs around Choubar, Haviq, and Keshli.
Coastal Areas: The shores of the Caspian Sea are among the lowland shores and beaches (sand and gravel). The recession and advancement of sea water along with high water levels in aquifers are bottlenecks and geomorphologic obstacles of the area which have changed into environmental problems in releasing urban and industrial wastewater in the city of Astara. It is recommended to prevent the construction of residential houses and structures which contribute to this waste.

Keywords

• reconstruction
• Gilan
• Karganrood
• Geomorphological indices

20.1001.1.23221682.1398.8.3.8.3

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