الملخص

the study of dhiban Fn.(Early Miocene )included the examination of four core holes . three of them the Shiekh Ibrahim area and one from Sasan area -west of mousl city . the succession of carbonates and Evaporates sedimentary facies indicated the deposition of Dhiban Fn.sediments in coastal lagoons and adjacent tidal flats which have developed as a consequence of sea regression through the second sedimentary cycle of lower Miocene. Isopach map of the region shows that Shiekh ibrahim areawasthe north eastern marcgin of the basin during this cycle. the configuration of diagenetic processes and in particular dolomitization of the dhiban and older rocks ( Euphrates and Serekagni Fns.) in the sequence cuold be interpolated via a vcariety of mechanisms namely: reflux, mixing and evaporativce pumping.