ANALYSIS OF REEF SEDIMENTATION IN HURGHADA (EGYPT), NORTHERN RED-SEA

A facies model for sedimentation on a patch reef near Hurghada, northe rn Red Sea Egypt has been developed. This model is based on field obse rvations, results of laboratory analyses (textural, mineralogical, geo chemical and petrographical analyses) and multivariate statistical ana lyses of reef sediments collected from different zones in the study ar ea Results of laboratory analyses of 28 samples suggested that the sed iments exhibit remarkable variations within the study area Statistical classification of the sediments allows determination of three facies: Siliciclastic/Carbonate facies: Includes samples from beach and back- reef zones and was recognized on the basis of Foraminifera/Mn-Ba-Mg-Fe /Dolomite-Protodolomite composition. The nature and distribution of se diments in this facies suggest that a combination of biological, chemi cal and physical processes influence the sedimentation. Biotype/Aragon ite facies:-Includes those samples from the reef-flat and close to the reef formations and was recognized on the basis of coral/ aragonite c omposition. The distribution of sediments and sedimentation in this fa cies is controlled by biological and chemical factors. Textural/Iron-r ich/Mg-calcite facies:-Includes those samples locate offshore, away fr om reef formations when the depth exceeds 25 m. This facies was recogn ized on the basis of sediments size/Fe content and Mg-calcite content. The distribution and the composition of the sediments in this facies are controlled by chemical and hydrochemical factors.