Unconsolidated reefal sediments in the Jubal Strait region, Red Sea, Egypt

Abstract

The Strait of Jubal lies in a geologically active zone forming the junction between the old Gulf of Suez and the comparatively younger Red Sea. The western side of the strait is bordered by a series of high islands and extensive coral reef formations. The coast of the mainland is characterized by a developing fringing reef and intense sedimentation of terrigenous clastics. This area is under the influence of an arid climate and strong tidal currents. The beach and bottom sediments have different origins: the beach sediments are siliciclastics of terrigenous origin, whereas the bottom sediments comprise carbonate reef products. Both sediment types are poorly sorted, reflecting the instability of the hydrodynamic conditions and the high rate of sedimentation. It appears that lime mud originates in the northern, agitated part of the area and drifts southeastwards to become trapped in the deep-water areas. The mineral assemblage of the reefal sands comprises high-Mg calcite, aragonite and low-Mg calcite, in decreasing order of abundance, while the lime mud is composed of low-Mg calcite, calcite and aragonite. The terrigenous mineral association of the beach sands includes quartz and feldspars. Magnetite and ilmenite are the most common heavy minerals.