Active tectonic assessment in the central Makran accretionary wedge (SE Iran): a comparison between field survey data and geomorphic study

This study provides morphology and field survey data on Ghasr-e-Ghand and Kahorkan thrusts, in the central part of eastern Makran accretionary wedge, in southeast Iran. The N-dipping thrusts with E-W strike, which brought Upper Oligocene turbidites onto Lower-Middle Miocene sediments, are one of the most important structure in this area and separate Inner Makran to the north from Outer Makran in the south. A clear facies changes are recorded in hanging wall of Ghasr-e-Ghand thrust, i.e. from shale in the east to sandstone-dominated to the West.
We combined the field data with geomorphic indices and show how lithology changes along Ghasr-e-Ghand Thrust influenced topography and morphology and so reveal not reliable active tectonic areas in view of geomorphic processing.
Materials and MethodesMorphotectonic indices, Stream Length-Gradient (SL), Mountain Front Sinuosity (Smf) and hypsometric integral (Hi), which are sensitive to uplift and topography changes, are used to determine the tectonic activities along Ghasr-e-Ghand and Kahorkan thrusts. 78 adjacent catchment draining are extracted by ArcGIS 10.1 and Arc hydro software in the study area.
Field survey data were used to determine kinematic and recent activities of the thrusts, based on measurements along the thrusts, lithologic observations and stratigraphic relations across the faults.
The results of morphotectonic and field data as well as geological map and Digital Elevation Model (DEM) are combined in ArcGIS software as different layer to determine relationship between the layers and their effect on morphology of the area.
Results and DiscussionThe morphotectonic analysis consist of low value (ConclusionsField survey data indicate a recent tectonic activity for the eastern segment of Ghasr-Ghand thrust, which is in contrast with morphotectonic analysis. We believe facies changes in hanging wall of the thrust, caused different lithology with different strength and so different behavior in erosion along the thrust, which caused lower topography in the eastern segment with outcrops of shale in hanging wall to higher topography in the western segment with outcrops of volcanoclastic sandstone. Some E-W mountain, south of Ghasr-e-Ghand and Kahorkan thusts, make a sharp front without present of faults in the northern flank. Different lithologic strength caused to have such a landscape in the southern part of Makran.