The lithostratigraphy and microfacies analysis of three selected stratigraphic sections werernstudied using field data and about thirty four thin sections analysis. These were used tornunderstand the depositional environments, diagenetic settings and age of the carbonaternsuccession (the Antalo Limestone Formation) of the Dire Dawa area, in South EasternrnEthiopia.rnThe field observations, microfacies analysis, and biostratigraphic examinations on therncarbonate successions of the area, which sandwiched between lower and Upper Sandstonernunits, reveal that: these carbonate units have about (~306 m) thickness , have beenrndeposited during Bathonian-Kimmeridgian time; and can be sub-divided into three sub-units,rnaccording to their facies contents and stratigraphic positions. These, from older to youngerrnare: (1) The lower sub-unit (Bathonian-Callovian) which is (~119m) thick and consists ofrnmixed siliciclastic - carbonates units of tidalflat-lagoon deposits; and peloidal and ooiliticrngrainstone facies of carbonate shoal/barrier deposits of the shallow marine setting, (2)Thernmiddle sub-unit(Oxfordian-lower Kimmeridgian) is about (~84m ) thick , conformablyrnoverlies the lower sub-unit , consists of the foreshoal facies of thick, allochemical richrnwackestone-grainstone limestones, mainly dominated by reworked intraclastic grains andrnrare amounts of patches of colonial organisms, and (3) The upper sub-unit (Kimmeridgian)rnis about (~103m) thick, overlies the middle sub-unit conformably and topped unconformablyrnby the Upper Sandstone. It consist of low energy deposits of fine grained dark micriticrnlimestones with some cherts and clastic shale interbedded at its lower; and some colonial andrncarbonate buildup organism bearing layers at its upper part.rnThe overall microfacies and facies successions throughout the unit shows a carbonate ramprndepositional setting , under which various submarine depositional environments rangingrnfrom shoreline carbonate deposits( including low energy tidalflat and lagoon) and highrnenergy platform margin carbonate sand bodies) of inner ramp , foreshoal deposits of midramprnto the offshore deposits(basin margins and open sea) of outer ramp, successively fromrnbottom to top.rnThe diagenetic sequence of these carbonate units, when ordered form early to late stage,rncomprises the following: micritization, dissolution, early marine cementation, meteoricrncalcite cementation, mechanical and chemical compaction, fractures; stylolitization,rndolomitization, silicification and burial cementation. These processes have taken place withrnvarying intensities and occurrence throughout the area.rnLastly deposition and facies patterns throughout this unit are related to already establishedrnpaleogeoraphic changes particularly involving the transgression of the sea on the horn ofrnAfrica. These deposits are also correlated with some of equivalent deposits in majorrnEthiopian sedimentary basins and with the Sana a basin of Yemen.