Main drivers of drainage pattern development in onshore makran accretionary wedge, se Iran

Abstract

Over time, river networks achieve a specific pattern as determined by the function of several factors such as climate, tectonic, geological structures, topography, lithology, and base-level fluctuations. The relative importance of mentioned factors on drainage systems was studied to determine the controlling factors of their heterogeneity across the tectono-stratigraphic zones of onshore Iranian Makran. We applied structural, geomorphological, and climate analysis. Results indicate that the dendritic patterns of N-S flowing rivers in the western part of Iranian Makran are mostly controlled by the Minab-Zendan Fault activity and distribution of olistostrome cover, whereas the dominant trellis patterns in the eastern part are controlled by the well-developed thrust fault-related fold systems. The channel steepness pattern demonstrates that the high values are mostly localized in the hanging wall of thrust and normal faults. Accordingly, the topographic profiles of the steep rivers show the old stages of incision in the Inner and Outer Makran. However, some rivers of the Coastal Makran are in the young stage of incision, where the normal faults are located and active. The sediment connectivity index shows that the Inner Makran has a high potential of sediment supplies, while the Outer Makran intra-mountain basins and the Coastal-plain are more prone to sediments accumulation. Our findings reveal that the river patterns and landscape evolution in the Inner and Outer Makran are controlled by thrust faults, olistostrome and related mini-basins, while rivers in the Coastal Makran are governed by activity of Pliocene-Pleistocene normal faults.