مطالعه خاكشناسي منطقه طالقان با استفاده از روش زمين شناسي

Investigating Pedology of Taleghan by Using Geological Method

In this research, lithologic-geologic characterstics and the relationship between lithology and pedology of the studied area were investigated. The area studied consists of six chosen watersheds of the Taleghan Drainage Basin which are located in 50° 20ʹ to 51° 10ʹ longitude and 36° 05ʹ to 36° 23ʹ latitude. The six sub-catchments were chosen in such a way that every two of them were located against each other and in opposite geographic aspects. The area is located in Alborz geological zone and in central Alborz sub-zone. From the view point of seismicity, the area is active. The major faults of the area are Taleghan and Kandevan faults and a few other minor ones. Some branches of these faults are present in the area. Stratigraphically, from the oldest formations (belonging to pre-Cambrian) to the youngest formations (belonging to Quaternary) are present with diverse lithological characteristics. In the area, sedimentary rocks and evaporites outcrop. Igneos rocks are widespread. Extrusive igneous rocks consist of pyroclastics and lava flows. Intrusive igneous rocks are also present. In this paper, by photogeologic investigations and field checks, geology and lithology maps of the watersheds with the scale of 1:25000 were prepared. Then, several soil profiles were made on each lithologic unit from which soil samples were taken. Soil samples were then analyzed in the lab. The results of these analyses show that soil characteristics were dependent on chemical and physical properties of parent rocks. The soils formed on limestones had high percentage of CaCO3, alkaline pH and low EC. Soils formed on evaporitic marls had clayey texture, relatively high CaCO3% and EC, and alkaline pH. The Soils formed on acidic (Sialic) igneous rocks had acidic pH, and very low EC and CaCO3%, and mainly sandy texture. Soils formed on intermediate igneous rocks had neutral pH of 7 and low EC and CaCO3% and predominately sandy texture. soils formed on igneous rocks had a pH of 7.225, intermediate to high CaCO3%, low EC, and predominately sandy texture.