Sedimentological Study of the Balambo Formation (lower Cretaceous) in the Exposed Part of the Selected Section from Choman Area, Erbil, Iraqi- Kurdistan Region

A detailed sedimentology of the Balambo Formation (lower Cretaceous) including petrography, mineralogy, microfacies analysis and depositional environment in Razan section, Northeastern Iraq has been conducted. The formation is comprised of alternation of thin to medium, yellowish grey and grey marly limestone, medium bedded limestone, thin bedded dark grey to black shales, thin bedded grey to green marl with dark bands and nodules of chert. Based on the petrographic investigation, the main skeletal grains in carbonate of Balambo Formation include planktonic foraminifera, calcispheres and radiolaria. The major diagenetic processes affecting the carbonate of the formation include micritization, neomorphism, dolomitization, cementation, compaction, dissolution and pyritization. Some marl and shale samples are subjected to X-ray diffraction investigation, which revealed that the non-clay minerals are pyrite, dolomite, quartz, and calcite, while the clay minerals are kaolinite and illite. To ascertain and interpret the depositional environment of the formation, three primary microfacies are identified in the carbonate of the Balambo Formation and then subdivided into six submicrofacies. Petrographic examination and microfacies research show that a basinal, deep-water environment is where the Balambo Formation in the Razan section had been deposited.