Structural and Paleostress analysis in the western Makran fold and thrust belt in Iran; Darivar area

The Makran Accretionary Wedge is formed by ongoing northward subduction of the oceanic part of the Arabian plate beneath the Lut, in Iran, and Afghan blocks as a part of Eurasia. The wedge, with excellent outcrops in land as well as poor vegetation caused to be an excellent example to study the structures of active convergent plate boundary involving subduction of the oceanic lithosphere. The wedge consists of Eocene turbidites, located in north of the study area, western part of the Makran, which thrust over the Upper Oligocene and Miocene sediments, as a part of the study area. These sedimentary units thrust over the younger sediments, Middle to Late Miocene, located in southern part of the wedge. Measurements of fault planes and slicken lines indicate that the main faults are NEdipping reverse faults with top to South movements. Asymmetric anticlines with high angle in foreland limbs, even overturned, in hanging walls of the thrust indicate fold propagation fault systems. Close to tight S-vergent chevron folds with almost WNW-ESE trends are common in the older units, older than Late Oligocene. In contrast the younger units consist of open, rounded and usually symmetric folds. However the trends of structures are same in all part of the study area. Paleostress analysis based on geometry, kinematics of fault data by fault-slip inversion method was performed from the striations or the slicken lines data collected from the faults planes. The results of 112 fault data taken in six station indicate high angle plunge for minimum principal stress, which suggest a compression regime for the study area. The orientations of the mean maximum principal stress (σ1) is N050°, 06° and the mean minimum principal stress (σ3) is N140°,80°. The NNE–SSW compression direction is consistent with the direction of structures, fold and faults, in the study area, Which could indicate a continues and same direction of shortening.