839 Journal of Oceanography, Vol. 62, pp. 839 to 849, 2006 Keywords: ⋅ Marine sediments, ⋅ terrigenous, ⋅ carbonate, ⋅ texture, ⋅ Gulf of Aqaba. * Corresponding author. E-mail: s.rousan@ju.edu.jo Copyright©The Oceanographic Society of Japan/TERRAPUB/Springer Geochemical and Textural Properties of Carbonate and Terrigenous Sediments along the Jordanian Coast of the Gulf of Aqaba SABER AL-ROUSAN*, MOHAMMED RASHEED, FUAD AL-HORANI and RIYAD MANASRAH Marine Science Station, The University of Jordan & Yarmouk University, P.O. Box 195, 77110 Aqaba, Jordan (Received 18 January 2006; in revised form 12 July 2006; accepted 12 July 2006) The physicochemical properties of 21 marine sediment samples were investigated, collected from five different localities along the Jordanian coast of the Gulf of Aqaba. According to the chemical parameters, sediments were categorized into three groups: carbonate (80% CaCO 3 ), composed mainly of materials of calcareous skeletal struc- tures; terrigenous (<10% CaCO 3 ) depositional areas for land-derived materials from surrounding rocks and alluviums; and a admixture of the first two (19–37% CaCO 3 ). High significant linear correlations were found between organic carbon (OC) and total nitrogen (TN), indicating the occurrence of these components in a common phase (organic matter). Despite the co-occurrence of TP in organic matter, these two ele- ments were negatively correlated, indicating anthropogenic sources of pollution such as phosphate exportation (hotel areas and clinker port sites) and industrial activities (industrial complex site). The study found that variations in texture properties and mud contents were due to differences in sediment sources, topography and their re- sponse during currents and waves. The finer, well-sorted sediments contain lower elemental concentrations of OC, calcium carbonate and TN (excluding TP) than coarser, poorly-sorted sediments. of the deposited organic matter is degraded, remineralized in the sediment and returns as inorganic nutrient, such as nitrogen, phosphorus and silicon, to the overlying waters (Reddy and Patrick, 1984; Boynton and Kemp, 1985; Capone et al., 1992; Howarth et al., 1995; Al-Rousan et al., 2004). Bottom sediments also act as a sink for the different pollutants which enter the sea through anthro- pogenic sources. Carbonate and terrigenous sediments differ in their chemical and physical characteristics, such as porosity, light attenuation, surface structure, sorption and desorption characteristics and dissolution kinetics (Schroeder and Purser, 1986). An understanding of the physicochemical properties of marine sediments in coral reef areas is important for estimation of inorganic nutri- ent fluxes between the bottom and the water column, which in turn influence the overall community of the nearby environment. This study is important in areas where heterogeneous sources of sediments prevail such as the Gulf of Aqaba and similar areas in the world. A knowledge of sediment composition provides an impor- tant clue about the origin of the individual grains, while textural characteristics provide information about energy 1. Introduction In tropical and subtropical environments, sediments in coastal zones are frequently dominated by biogenic sands. The unconsolidated reef sediments constitute the major proportion of the surface area of the coral reefs (Furnas et al., 1995). These loose sediments, containing carbonate skeletons of corals and other reef organisms, accumulate near the coral reefs and can be a result of the disintegration of reef rock, solid biogenic material, pri- mary clastic debris, beach rock fragments and/or fecal materials (Friedman, 1968; Mantaggioni and Gabrie, 1982; Sorkin, 1995; Rasheed et al ., 2004a). However, input of terrigenous materials may be significant in coastal fringing reefs. Many reef flats contain little loose sedi- ment except in depressions or leeward of large coral heads. Marine sediments comprise about 10% of the oceanic floor where 20–30% of the oceanic primary production and about 85% of the total organic matter sedimentation takes place (Jorgensen, 1983; Romankevich, 1984). Most