Estimating the rate of shortening and the role of decollement in western Kopet-Dagh deformation

The kopet- Dagh zone undergone subsidence and deposition of sediments after middle Cimmerian orogeny in middle Jurassic to Eocene. Its shortening resulted from the Zagros orogeny in Paleogene. In order to identify the minerals at the detachments, XRD analysis was carried on the samples of Shemshak and Chamanbid Formations. On the other hand, the estimated shortening in the west and central Kopet-Dagh in two north-south cross-sections, were calculated in the 3D software of Move-Midland Valley, using previous data, field observation, geological maps and satellite images. The study of the three-dimensional cross sections, which is considered to be the innovations of this research, in the Move software has shown that most of the anticlines of the region are asymmetric due to the operation of detachment horizons. The results of the analyses indicate that the Shamshak Formation has more potential for developing detachment surfaces than the Chamanbide Formation. The reason for this detachment surface is due to thickness and mineralogy of the Shemshak Formation. On the other hand, by using geometric relationships, the depth of detachments was calculated for the main folds. In most of the detachments, this depth was calculated at lower levels of the Shemshak Formation.