Abstract: Diagenetıc quartz crystals with different textural features are observed as cement and replacement in various lit/iologies andfossils of the Berdiga limestone of Upper Jurassic-Lower Cretaceous age which has widespread exposures in eastern Pontids. Spongia spicules, radiolarian tests, clay stones, granitic and volcanic rocks rich in K-feldspar is the source for the silica required for theformation of diagenetic quartz.Various models have been proposed to explain the dissolution of carbonates and/or the replacement of carbonates by silica. Themost appropriate model is the one which explains that silicification observed in the Berdiga limestone is likely to be due to a replacment mechanism controlled by the force of crystallization. The other models (especially bacterial decay of organic substances) mayhave played a role locally during the ini t at i on of silicification of carbonates.Comparasion of diagenetic qucutz types found in the Berdiga limestone with various diagenetic environments and/or diageneticproducts of these environments has shown that diagenetic quartz crystals are not contemporaneous, and that, depending ont he timedepth function (together with volumetric shrinkage) they are observed to change from chalcedony-to quartzine-to microcrystallinequartz-and to megaquartz from shallow to deep burial environments.