Texture and mineralogy of the surface sediments of Sharm Obhur, west Red Sea coast of Saudi Arabia

Abstract

The present paper deals with the study of the grain-size characteristics and the mineralogy of the bottom and beach sediments of Sharm Obhur. Most of the sediments are in digenous carbonates with little terrigenous material. A major part of the Sharm is covered with coarse to medium-grained sediments. Heavy minerals make up 5 to 15% of the samples and are mainly composed of amphiboles, pyroxenes, biotite, epidote and opaques. The heavy-mineral suite is apparently derived mainly from metamorphic source rocks with minor contribution from basalts. The content of high-Mg calcite decreases landward in the Sharm due to more inorganic precipitation of carbonate in the form of aragonite. The high content of calcite in the beach sands from the shoreline of the Sharm shows that the calcite-rich old reef limestones that crop out along the Sharm contribute considerable material of the beach sediments. Kaolinite, mixed-layer chlorite—vermiculite and illite are the dominant clay minerals. The alluvium derived from the low-grade metamorphic rocks and basalts of the Jeddah Group forms the source of the clay minerals.