عنوان مقاله [English]
Continuation of the compressional regime within the convergence zone between the Central Iran and Turan rigid blocks caused thrusting of old rock complexes over the recent sediments. As a result of multiple thrusts and folds, the area uplifted at the same time and the Binalud range have been shortened. This study attempts to evaluate the amount of shortening of the Binalud mountains by reconstruction of a balanced cross-section. Field data from the Dulat-Abad-Neyshbur transect, study of the geological units and décollements along the section, and the Move® software environment are used as the basis for this research. Based on these information, four tests were carried out for balancing the cross section in question. The first test, which used the arc and polygon method for the horizons and a listric fault without floor thrust, failed to display the deformed section. In the second test the section was drawn, however the deformed structure did not balance the section in the process of unfolding the fault bend folds. In the third and fourth tests, we used the kink method to restore the deformed state to an undeformed section. For the third test, deformation was proceeded from the hinterland, and in the process of restoration, a shortening of about 65% was revealed. The fourth test was proceeded from the foreland, and taking into account both the foreland uplifts and shortening, the amount of shortening of Binalud range was estimated to about 26%. The final structural model defined a thin-skinned fold and thrust belt which included fault-bend-folds with out-of-sequence and in sequence duplexes. Major décollement horizons defined in the region include: 1) shale horizons within the Silurian-Devonian rock units, 2) medium-bedded dolomite and limestone layers within the Bahram Formation, and 3) evaporitic layers in the Eocene sediments.