Role of Active tectonics on the formation of Garaghe closed basin, Zahedan

Garagheh closed basin is located in the west and northwest of Zahedan city and in the middle of Sistan Suture Zone. The presence of this basin with a large area that located in a shear-compressional Sistan Suture Zone that surrounded by numerous faults can be a subject for study of active tectonics in this area. Based on field study and the relationship between tectonic structures, the development of this basin has been investigated. We applied the geomorphic indices such as mountain-front sinuosity (SMF), asymmetry factor of drainage basin (AF), hypsometric integral (HI), basin shape (BS), mean axial slope of channel (MASC), valley floor width –valley height ratio (VF), relative assessment of tectonic activity (Iat) to evaluate tectonic activity of 378 sub-basins. The results suggest that the main basin is active and asymmetric but the activity of sub-basins are different throughout the study area. High active sub-basins are mainly located around the main basin and associated with active faults but less active basins are mainly located in the center. The relationship between shape of main basin and active faults shows, depending on the shape of the basin, the faults are close to each other in the north and northwest and far apart in the south and southeast. These results suggest a counter clockwise rotation of faults caused a tectonic rotation that creates a transtensional deformation that form a closed Garagheh Basin.