BOTTOM SEDIMENTS OF THE ARABIAN GULF .1. SEDIMENTOLOGICAL CHARACTERISTICS

More than 100 bottom sediment samples of the Arabian Gulf were collect ed during a cruise in 1992. The area was covered through 17 traverses in a northeast-southwest direction to the axis of the Gulf. Sedimentol ogical analyses were done for fifty-six samples of reasonable volume. The recent marine bottom sediments of the Gulf are subdivided into sev en textural classes: sand, silty sand, muddy sand, sandy silt, sandy m ud, silt, and mud. Most of the study area is covered by muddy sediment s, whereas sandy deposits are restricted to the western part (offshore Qatar and the United Arab Emarites) and around islands and bathymetri c highs. The counter-clockwise circulation of current from the Indian Ocean probably led to deposition of finer sediments along the eastern (Iranian) side. Sediments along the eastern and north-western margins are poorly sorted, probably due to the effect of tidal currents, river influx and eolian deposition. Suspension is thought to be the most im portant process of transportation and deposition, hence low energy con ditions prevail in these areas, particularly in the northern part. Sed imentological characteristics reflect the interaction between autochth onous calcareous fragments mostly of biogenic origin, rock fragments d erived from beachrocks and submerged reef Bats, and allochthonous terr igenous detritus supplied to the area by dust storms and river deltas in the north and east. Based on sediment distribution, the magnitude o f bottom currents and the topographic nature of the Arabian Gulf, a no rth-south sediment transport from the northern part, parallel to the a xis of the Gulf, is inferred.