Petrography, Facies Analysis, and Depositional Environment of the Sargelu Formation (Middle Jurassic), in a Selected Section, Northeastern Iraq

The study deals with the sedimentology of the Middle Jurassic Sargelu Formation and its implications for facies analysis and depositional environment. The studied section is located in Sulaymaniyah City, between the Sargelu and Goshan villages, within the Highfolded Zone, northeastern Kurdistan Region of Iraq. In the study area, the formation is characterized by a succession of limestone interbedded with thin beds of dolomite and thin shale. It overlies the Sehkaniyan Formation and underlies the Naokelekan Formation. Twenty-two thin sections from the limestone succession were chosen for petrographic analysis using a polarizing microscope to determine their petrographic constituents. The petrographic study of carbonate units showed that they consist mainly of skeletal grains (calcospheres, radiolaria, pelecypods, planktonic foraminifera, and ostracods). The successions were affected by several diagenetic processes such as recrystallization, dolomitization, compaction, and Pyritization. Three different microfacies were recognized that showed a wide range of facies associations. These are further subdivided into eight sub-microfacies, suggesting the deposition of the Sargelu Formation in the deep shelf and deep marine basinal environments.