Yamama Formation (Late Berriasian–Valangenian) forms the most important Lower Cretaceous carbonate reservoir in the south of Iraq. The petrographic study by thin-section examination indicates that the Yamama Formation in Tuba Oil Field had been affected by nine diagenetic processes. These processes ruled the porosity system in this formation, these processes are; cementation, micritization, pyritization, silicification, dissolution, mechanical compaction, chemical compaction (stylolization), dolomitization, and neomorphisim. The deposition of Yamama Formation was occurred during a regressive period within inner ramp, mid ramp, and outer ramp environments.

Diagenesis, Lower Cretaceous, Yamama Formation, Tuba Oil Field, Iraq.