The section located in WadiHajar, Haditha area, west of Iraq was sampled for microfacies analysis of the Euphrates Formation. Microfacies analysis led to the recognition of eleven microfacies association types; Mudstone, Peloidalgrainstone, ooidsgrainstone, Miliolids-Peneroplidsgrainstone, Peneroplidsgrainstone, Echinoidalwackestone, Miliolidswackestone, Alveolinidswackestone, Bioclasticpackstone, Peneroplidspackstone and Rotaliidspackstone, were deposited in restricted marine, shoal, and open marine environments. The study of the vertical succession of microfacies shows four primary 4th order cycles (1, 2, 3, and 4) each show a different episode of stills tands sea level rises. Cycle 1 is represented by LST of basal conglomerate followed by a thick succession of open marine facies of TST, overlain by sh0rt episode of still stand. According to minor sea level changes, cycle 2 is subdivided into 2a, 2b, and 2c consisting TST of bioclastic, miliolids, peloidswackestone to packstone, followed by thin HST consisting restricted marine facies. Cycle 3 consists of a short episode of sea level rise of TST followed by a long episode of sea level still standing and subdivided into 3a and 3b. Cycle 4 is marked by open marine facies (TST), overlain by HST of restricted marine facies. The low subsidence rate and eustatic sea-level fluctuation are the main factors that affect the study area. Manuscript profile