Paleostress and structural analysis in the western Makran accretionary wedge in Iran; Sit area

The active Makran accretionary wedge, located in SE Iran and S of Pakistan, presumably is the largest accretionary complex in the world. The Makran accretionary wedge with width of 350 km, grows both vertically and laterally by shortening and scraping sediment material of the shallow dipping northwards subducting Arabian lithosphere. The onshore accretionary wedge is divided into three tectono-stratigraphy units, Inner-Outer- and Coastal Makran from north to south. The wedge consists of Eocene turbidites in northern part, Inner Makran, thrusted over the Oligocene-Miocene sediments in the Outer Makran and this unit is located on the Upper Miocene sediments, crops out in the Coastal Makran by series of thrusts. The study area is located in west of the Makran fold and thrust belt, Sit area, in the Outer- and Coastal Makran, which consists of WNW-SSE thrusts, backthrusts and folds. The folds are almost symmetric with large wave length of 8 km in the Miocene sediments, usually maller and a symmetric folds, S-vergence, are common in the shale and marl units, near to the fault zones. The thrusts are extended in the soft units in the study area, i.e. Lower-Middle Miocene shale units. The thrusts are shallow N-dipping with the movements of top to the south, usually. Flat to S-dipping faults in the thrust zone indicate a foreland dipping duplex, which caused to have klippes due to movements of the material in hangingwall. Large Sdipping back thrusts are evolved in the same soft units. We believe these soft units play as décolments role. Paleostress analysis is done to obtain the orientation of the principal stress directions, based on geometry and kinematic of faults such as slicken lines, fault movements and fault plane properties. In total 70 fault measured that including 5 stations in the study area. The minimum principal stresses have high plunge 80º, which according to Anderson s theory, suggest a compression regime for the study area. A general NNE–SSW compression regime is calculated that almost consistent with trends of faults and folds in the study and adjust area.