Environmental implications of the distribution and physical characteristics of surface sediments in the northern Persian Gulf

摘要

The Persian Gulf (PG) is a marginal sea with unique geomorphology and ocean currents, as well as various sub-basins with specific sediment characteristics. In this study, grain size distribution and microscopic examination of coarse-grained particles of 52 surface sediments of the Iranian part of the PG were performed to assess the distribution and physical characteristics of surface sediments and their link to the environmental conditions. Results showed that the seafloor of the middle parts of the PG bottom is covered by silt and sandy silt with a coarsening trend from shallower to deeper waters. At the NW part (submerged Arvand Delta) and the SE part (Strait of Hormoz) of the PG, however, coarser grains of silty sand, and locally, gravelly muddy sand dominate. High-energy density-driven bottom current leaving the PG from channelized deeper areas is likely responsible for removing fine grains, resulting in the accumulation of very poorly to poorly sorted coarse sediments (shell fragments and relict particles) in the deep bottom areas. This hard bottom, in turn, provides a proper surface for some epifaunal communities such as corals and foraminifera. The Iranian offshore basins, on the other hand, are dominated by well to moderately sorted silt to fine sand terrigenous particles. These finer sediments contain a relatively high organic matter with high pellet contents. Altogether, the sedimentation regime of the basin is under the influence of complex hydrodynamic conditions, different bottom materials (relict and bioclasts), the proportion of terrigenous components, complex bottom topography and climate.