Sedimentary variations of geomorphic subenvironments at Al-Lith area, central-west coast of Saudi Arabia, Red Sea

摘要

Sediment characteristics are the indicators of the intensity and geological history of the processes active in an area. Their association with different geomorphic features also signifies the present day conditions of deposition. In this study, variations in sediment characteristics associated with different geomorphic features, such as the coastal zone, two islands and a lagoon in the Al-Lith area of central-west coast of Saudi Arabia have been analysed. Whereas, the detrital sediments (sand+mud) are common (61-87 %) in most of the subunits of the coastal zone; the nondetrital (carbonate rich) sediments are more common (54-95 %) on the two islands as well as the lagoon; indicating distinct sources of sediments in these regions. The variation of sediment texture between sand and sandy silt in most geomorphic units, also shows that they are exposed to highenergy conditions, whereas occurrence of heavy minerals in small proportions (<7 %) indicates limited inputs from landbased igneous and metamorphic rocks. Sediment mean size vs. standard deviation shows that the sediment characteristics of a geomorphic unit (e.g. beach or sand bar) on the coast and on the island are different owing to different processes responsible for their formation.