Abstract: The study investigated phosphate-rich sedimentary rocks in the Late Cretaceous Karababa Formation inthe Mardin-Mazıdağ region, which represents the northern part of the Arabian Plate. The stratigraphic successionis divided in three members as i) Karataş: ellipsoidal gray-colored, largely weathered, fossiliferous shelly micriticlimestone, ii) Ekinciler: dolomitic cherty limestone interbedded with marls, and iii) Evciler: argillaceous limestonewith common phosphatic horizons. Large numbers of hand samples, collected from the outcrop successions, werecarefully studied with optic microscopy (OM) and scanning electron microscopy (SEM). They indicate the presenceof optical isotropic pelletic apatite minerals (37% P2O5), bone fragments, fish teeth, and invertebrate fossil fragmentslike brachiopod shells in phosphorite rocks and micritic limestone. The phosphorites in the Karababa Formation areinterpreted to have been deposited in a very shallow, near-shore low energy environment. The X-ray diffraction  (XRD) method confirmed the presence of apatite (carbonate fluorapatite: CFA), calcite, quartz, rare feldspar,dolomite, and clay (smectite, palygorskite, illite, kaolinite, chlorite, sepiolite, mixed layered illite-vermiculite, andchlorite-vermiculite) in phosphatic, silicic and other carbonate rocks. Total trace element concentrations in apatiteminerals range from 2436 ppm to 2456 ppm, with total concentrations normalized to chondrite (ppm) higher thanNorth America Shale Composite (NASC) at 664.98 ppm for P, 208.33 ppm for Sr and 33.66 ppm for Y. Commonoccurences of apatite, palygorskite/sepiolite, and smectite clay minerals in various sections of the KarababaFormation were interpreted as authigenic minerals in the marine environment. However, occurrences of mixedlayered clay minerals were interpreted as a result of neoformation and/or transformation processes. The phosphateoccurences in the Karababa Formation are considered to form due to mineral formation processes occurring viabiogenic and biogeochemical activities that developed with the changes in sea level linked to tectonic movementsassociated with the evolution of the Neotethyan ocean during the Upper Cretaceous period.