| Abstract: |
The studied Middle to Upper Miocene Abu Dabbab evaporites at the coastal plains of the Red Sea represent the middle belt that is bounded to the west by the Lower Miocene clastics of the Ranga Formation, and the carbonates of Um Mahara Formation, and to thThe present work deals with the geological features, sedimentological characteristics and origin of evaporite deposits in Wadi Gasus, Wadi Teaban, and Wadi Wizr areas, located along the Re Sea coastal plain between Safaga and Mersa Alam from north to soutGeomorphologically, The studied areas are bounded on the east by the recent sediments of the shoreline of the Red Sea. Most of the sedimentary rocks in the three studied areas are of relatively moderate to low relief and its elevation decrease generally tThe three areas under study, wadi Gasus, wadi Teaban, and wadi Wizr contains economic gypsum deposits, with respect to the grade agent. The quantities of gypsum and anhydrite which used for industrial proposes (manufacture of gypsum for building proposes,The exposed rock units at wadi Wizr are represented by the basement rocks (various igneous and metamorphic rocks; the pink granite is the common rock type), of Precambrian age. The Nubian Formation consists of two Members; (A) Taref Sandstone Member, ConiIn wadi Teaban and wadi Gasus areas the Nubian formation, consists of the two Members Taref Sandstone Member and Quseir Clastic Member. The Cretaceous sediments (Nakheil, Thebes (the top part of all the high hills in the study areas), Esna, Tarawan, Duwi In the study areas two Middle Miocene formations, were recorded, 1-Gebel El Rusas Formation (consists of the lower clastics and upper carbonate units0, and 2 – Abu Dabbab Formation that represents the main sedimentary outcrops of the studied areas. It conThe evaporite rocks are differentiated into the following facies; 1 - Massive gypsum,2 - Regular laminated gypsum, 3 - Microbial laminated gypsum, 4 – Stromatolitic gypsum,5 - Nodular mosaic anhydrite, and 6 - Enterolithic anhydrite nodulesDiagenetically, the evaporite rocks have been affected during the three main stages; syndepositional stage, burial stage and uplift stage.Petrographic investigation show that the Middle to Upper Miocene Abu Dabbab evaporites of the northern Red Sea coastal plain of Egypt are composed mainly of secondary gypsum rocks that are mantled with 2-3 m thick anhydrite deposit. Several fabric types oThe fine alabastrine gypsum is formed in an active phreatic water condition and postdates the coarse porphyrotopic and poikilotopic gypsum by their dissolution and rapid crystal growth under disequilibrium condition. The gypsum veins represent excess voluWith regard to the geochemical characteristics of the studied gypsum, relatively higher concentration of FeO, MnO, k2O, MgO, TiO2, Sr, and Zr are observed. This indicates that the parent brine, from which the Red Sea gypsum was deposited, had relatively hEnvironmentally, the studied evaporite facies in the Red Sea region is either deposited in supratidal sabkha environment (nodular mosaic anhydrite and nodular enterolithic anhydrite) or shallow subaqueous (subtidal to intertidal) environment (regular lami
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