CLASSIFICATION AND DISTRIBUTION OF THE RED-SEA COASTAL SABKHAS NEAR JEDDAH-SAUDI-ARABIA

Sediment composition is an important factor in distinguishing sabkhas. Soluble salts (sulfates and chlorides), siliciclastic sediments, and carbonate minerals are the dominant components of sabkhas developed ar ound Sulaymaniya lagoon, located some 50 km north of Jeddah. By select ing different components as end members of a compositional triangle, a classification of sabkhas is proposed. Four stages of sabkha developm ent are recognized.namely the (1) incipient, (2) slightly developed, ( 3)moderately developed, and (4) well developed. Each type is divided i nto arenaceous or argillaceous depending on whether the insoluble frac tion is mainly composed of coarse- grained siliciclastic sediments or a combination of fine- grained siliciclastics, carbonate minerals, and organic matter. A detailed examination of the surface and near-surfac e features of each type of sabkha is made; and a map depicting sedimen t variation between sabkhas is prepared. The salinity of the water sam ples, collected from the boreholes located in different types of sabkh as, shows that the incipient- and slightly developed sabkhas are repre sented by very- saline- and slightly hypersaline waters. By contrast, the moderately to well- developed sabkhas are characterized by waters that are moderately to highly hypersaline. It is found that the spatia l pattern of geomorphic- and salinity zones is compatible with the dis tribution of sabkhas in the studied area.