Makran continental margin sedimentation during Late Holocene

Abstract

Sedimentation in the Makran active margin is governed by complex interaction of atmospheric, tectonics and hydrodynamic setting of northern flank of the Gulf of Oman. The mixed clastic carbonate sediments in tectonically and hydrodynamically active environment have complicated distribution pattern. The region is suffering from basic sedimentological data and specifically the sedimentation history of the Holocene deposits was rarely studied in Iranian coast. To deal with this deficiency, surface and core sediment samples from the Iranian continental shelf and upper slope of the Gulf of Oman have been studied using standard sedimentological techniques. The overall sediment distribution pattern demonstrates that the grain size gradually decreases from shoreline to the deeper zones. However, some medium to coarse grained sand patches can be found in deeper parts specially in the middle part of the studied area that can be related to sediment supply of ephemeral rivers discharging in to the sea in rainy seasons and/or high energy events i.e. turbidites and tsunamis during the Holocene. Several horizons of the coarse grained detrital sediments are detectable in upper slope sediment cores. The coarse grained materials are received from hinterland during flashfloods and could be accumulated due to mass wasting events. The elevated amount of organic materials in the upper slope indicates deficit of dissolved oxygen that leads to preservation of organic materials in the bottom sediments.