al lowed dis tin guish ing 26 microfacies, which can be grouped into twelve microfacies as so ci a tions that rep re sent four main depositional en vi ron ments: open-ma rine, outer-ramp, mid dle-ramp and in ner-ramp set tings. The car bon ates have un der - gone a com plex diagenetic his tory, from penecontemporaneous shal low-ma rine con sol i da tion to deep-burial diagenesis. The most im por tant pro cesses that af fected the car bon ates are dolomitization (in dif fer ent stages), ce men ta tion (by anhydrite and cal cite), dis so lu tion (fab ric-se lec tive and fab ric-de struc tive), frac tur ing, stylolitization and neomorphism. Mi nor diagenetic pro cesses that mod i fied the sed i ments are pyritization, sili ci fi ca tion, glauconitization, micritization and bio - turbation. Diagenetic pro cesses such as dolomitization, dis so lu tion and frac tur ing im proved the res er voir qual ity, whereas ce men ta tion and com pac tion have re duced the res er voir qual ity of the Asmari For ma tion. Whole-rock ox y gen and car bon iso tope anal y ses of lime stone sam ples show that the iso to pic com po si tion of the car bon ates was hardly af fected by diagenesis and that the car bon ates re mained roughly in iso to pic equi lib rium with the Paleogene sea wa ter. Some sam ples have, how ever, been af fected sig nif i cantly by diagenesis dur ing deep burial in a closed to semi-closed diagenetic sys tem.

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