Evaluation of the quantitative and qualitative relationship between springs and geological formations using geostatistics as well as Boolean logic in Iran

Abstract

Geologically, Mahdishahr watershed are considered as a part of the folds of the Alborz southern slopes in which we can find the signs of the first to third geological periods. This basin with an area of 1954 km2 is located in the north of Semnan. About 600 springs are found in this area. In the present study, geostatistics and Boolean logic is used to evaluate the correlation between the springs location, discharge, and EC with structural factors and geological formations. In order to assess the role of geological formations in quality and quantity of the springs discharge, after preparing a file of the springs location with 500, 1000, 2000, and 5000 m buffers, effective pre-Quaternary formations were counted based on the Boolean logic and geostatistical methods. The results of this study showed that most springs have been occurred in Shemshak, Elika, marl, and Eocene limestone (Elm) formations, respectively, which are followed by Laar, Ruteh, and Barut limestone formations. The most faults and fractures in this area have been occurred in the same formations, with the amount of 176, 98, 77, 71, 58, and 38 km, respectively. The highest discharge among the formations was devoted to Tizkuh formation, with an ultra-low EC value, while the highest EC value was observed in marl, and Eocene limestone formations. So, it can be concluded that faults and fractures of this area are closely related to the number of exposed springs, so that the faults of this area have increased the number of the springs and the type of the formation has controlled the amount of the springs discharge.