There Is Carbonate Unit Deposited In The Mekelle Outlier During The Upper Jurassic Period As ArnResult Of Flooding Of The Area By Paleotethys Ocean Toward The Southeast Direction. ThernMekelle Outlier Is Situated In The Northern Most Part Of Northwestern Plateau (NWP) And ThernStudy Carbonate Successions Are Aligned Along The Western (Hagere-Selam), Southeasternrn(Messsobo) And Northeastern (Wukro Section) Margin Of The Mekelle Outlier. This StudyrnFocused On Detailed Investigation Of Facies Analysis And Paleontology Of The Upper JurassicrnCarbonate Units In Order To Obtain A Detailed Picture Of Depositional Environment, AgernDetermination And Correlation. Three Main Methods Were Implemented In Order To AccomplishrnThe Stated Research Problem And Objective Of The Present Study. These Are Pre-Fieldwork, ArnDetailed Main Fieldwork And Laboratory Analysis (Petrographic Analysis, Micro And MacrornFossil Description And Systematics And Microfacies Analysis). A Total Of 65 Rocks And 26rnProductive Dry Marl Sediment Samples Are Collected From The Study Sections And ExaminedrnUnder Petrographic Microscope. Lithostratigraphically, The Carbonate Succession Has A TotalrnThickness About 400m, Which Is Characterized By Thin-Thick Bedded Limestone, Mudstone,rnFossiliferous, Coquinoidal, Oolitic And Sandy Limestone With Different Skeletal Components AndrnDifferent Sedimentary Structures. Based On A Detailed Field Investigation, Paleontological AndrnPetrographical Information, 19 Microfacies Type Are Recognized. These Are Grouped Into FourrnMicrofacies Association Including Tidal Flat (MFT1-3), Lagoon (MFL1-2), Shoal (MFS1-6) AndrnOpen Marine Environment (MFO1-8). Therefore, The Depositional System Of The CarbonaternSuccession Represents A Homoclinal Ramp Setting Because Of Thier Wide Lateral And VerticalrnDistribution Of Facies. Additionally, The Carbonate Units Of The Study Area Are Affected ByrnDifferent Diagenetic Features Including Compaction, Cementation, Dissolusion, Micrtization,rnDolomitization, Neomorphism, And Silicification. The Carbonate Rock Units Are CorrelatedrnWithin Different Measured Sections In The Mekelle Outlier And Regionally Correlated With ThernAntalo Limestone Of Blue Nile, The Urandab Formation Of Ogaden, The Antalo Limestone OfrnEretria And Other Arabian Platforms Based On Biostratigraphy And Lithostratigraphy.