Lithofacies analysis and depositional environments of the upper triassic and lower cretaceous sediments in euphrates graben syria

Abstract

© SGEM2019. The upper Triassic and lower Cretaceous sediments within the Euphrates graben are one of the most important oil and gas reservoirs to the east of Syria. Based on sedimentological investigations of core materials using methods of optical and scanning electron microscopes (SEM), accompanied with EDS and XRD analyses, four major lithofacies have been detected in the upper Triassic sediments, these include; 1) Lithofacies major sandstone bodies (code: Sst-1); up to 60 m in thickness, composed of medium to coarse-grained sandstones with clay material content up to 10%, they are interpreted as deposits of a meandering rivers. 2) Lithofacies minor sandstone bodies (code: Sst-2); thickness up to 4 m, consists of very fine to coarse-grained sandstones, with clay content up to 25%, they are interpreted as minor fluvial channels and crevasse supply deposits. 3) Lithofacies claystone (code: Cls-1); include several types of sublithofacies, and interpreted as floodplains deposits, 4) Lithofacies dolomite and dolomitic claystone (code: DClst-1); interpreted as lagoonal deposits formed in brackish water environments. Two major lithofacies have been detected in the lower Cretaceous sediments, these include; 1) Lithofacies claystone (code: Cls-2); form intervals of 1 to 10 m thickness, and has medium to moderate dark gray colors. The origin of the claystones are thought to be as deposition in moderately saturated environments with oxygen, marine or estuarial conditions of a low marsh. 2) Lithofacies sandstone bodies (code: Sst-3); among this lithofacies, several sublithofacies are detected. The sediments of this lithofacies and their sublithofacies are interpreted as sediments formed under the conditions of delta to coastal marine sediments.