The influence of hydrography, bathymetry and productivity on sediment type and composition of the Oman Margin and in the Northwest Arabian Sea

Abstract

Abstract The hydrography, bathymetry and sediment composition of the Oman Margin and NW Indian Ocean areas between latitudes 24°N and 13°N, have been studied. A pronounced oxygen minimum zone characterizes the water column between 200 and 1500 m depth and extends throughout the NW arabian Sea. The bathymetry of the margin is complex, resulting from tectonic movement along the Masirah Line. Small, anoxic intrashelf basins are developed south of Masirah. The Owen/Murray Ridge provides a barrier to westward progradation of terrigenous detritus from the Indus Fan. Upwelling and surface productivity result in the deposition of biogenic calcareous and siliceous sediments, the latter being restricted to the shelf and slope regions. Depositional controls, such as redistribution by bottom currents and bathymetry, greatly affect the quality of organic carbon deposited. Evidence is presented to suggest that much of the organic matter on the Oman shelf is degraded prior to burial. This has important connotations for sediment diagenesis and hydrocarbon maturation. The distribution of calcareous and siliceous sediments resulting from upwelling may well provide an index for determining the Neogene history of upwelling in the NW Arabian Sea.