الملخص

The Euphrates Formation (Early Miocene) was studied in three selected subsurface sections in the Hamrin oilfield in northern Iraq. The formation consists of limestone, dolomitic limestone, and dolomite. The petrographic study showed the dominance of the skeletal grains represented by the benthic foraminifera (Milliolid, Nummulites, Peneroplis, Dendritina, Miogypsina, Textularia and Ammonia) forming the most important genera available within the formation in addition to red algae, echinoderms, molluscs and bioclast, While the non-skeletal components constitute a smaller percentage compare to the skeletal grains and are represented by the peloids and intraclast. The matrix is composed mainly of micrite which is sometimes affected by the recrystallization process and transformed into microspar. According to the variety of petrographic constituents, five main microfacies were distinguished; Lime mudstone (Fm), wackestone (Fw), packestone (Fp), grainestone (Fg) and boundstone (Fb) which divided into fifteen submicrofacies. The sedimentary model represents deposition within a shallow marine environment extending from the lagoon to fore reef slope environments according to the facies analysis and their environmental implications and paleogeography of the Early Miocene. The rimmed platform model is the most acceptable model for the Euphrates Formation in the study area.