Erosión y desertificación.-Land degradation due to diapirs in Iran, case study: Hableh Rood drainage basin, east of Tehran

Abstract

ABSTRACT Different geological characteristics play role in Land degradation in Iran which are: 1-The abundance of Neogene evaporitic marly formations around and in desertic depression. These units have had important role in the formation of present landforms, are saline, alkaline and erodible and degrade the quality of water resources as diffuse and widespread sources and are endless sources for sand dunes. 2- The presence of numerous diapirs, some of which are salt domes consisting of halite. Due to diapirism, salts are now exposed at the surface of many parts of Iran and cause soil, surface and underground water and vegetation degradation as point sources. The importance of diapirism in geology of Iran has been emphasized previously. This paper intends to investigate the effect of salt domes in land degradation and propose restoration measures. Salt dome or diapire is a dome or anticlinal fold which due to the fact that salt has been intruded, the overlying rocks have been pierced and fractured. The process of movement and reaching of salt to the surface is called diapirism. Salt domes can be classified into active and inactive ones. Active diapirs are the ones which are still incorporating salt into the surrounding environment. They are usually young and play important role in degradation of natural resources. Solution of salt is continued. From the view point of geomorphology, they show irregular topography. One example of this kind of diapire is Kamaraj Salt Dome in Shahpour. Dalaki- Heleh Drainage Basin, Zagros Mountain Ranges, Iran. In this area, surface water resources are in constant contact with the salt. In inactive salt domes, diapirism has been terminated and most of the salt has been dissolved away. These diapirs are usually older in age and do not have important role in degradation of natural resources. In this research, diapirs of north of Great Kavir, in Central Iran Geological Zone, Hableh- Rood Drainage Basin, between Arzagh Bridge and Shahzadeh Hossein, northeast of Garmsar, southeast of Tehran, located in 35,15’ to 35, 25’ north latitude and 52, 20’ to 52, 30’ east longitude were investigated in detail. From the view point of structural geology, the studied area is located between Alborz Zone (soutern part) and and Central Iran Zone(northern part). Hableh Rood originates from mountains of northwest of Firooz-Kuh, drains Firruz-Kuh Plain and then reaches the studied area. Here, it receives Shor-Darreh whose watershed contains many active diapirs of Oligocene Age.