Depositional Setting of Khurmala Formation (Paleocene-Early Eocene) in Nerwa section, Berat Anticline, Kurdistan Region, Northern Iraq

Abstract

The depositional environment of the Khurmala Formation (Paleocene-Early Eocene) has been investigated in the Nerwa section, the southern limb of the Berat anticline in the High Folded Zone of Iraq. The thickness of the formation in the studied section was about 113m and can be divided into three units; fossiliferous bedded limestone unit (Unit A), massive dolomitic limestone unit (Unit B) and bedded marly dolomitic limestone unit (Unit C). The petrographic study of the 81 thin sections of the Khurmala carbonates revealed that the majority of skeletal grains are shallow marine derivative faunas and non-skeletal grains include peloids, cortoids and intraclasts. Depending on detailed field observations and petrographic study of the carbonate rocks, five main microfacies were recorded, these are; lime mudstone, lime wackestone, lime packstone, grainstone and boundstone in addition to one lithofacies which is an intraformational conglomerate. Based on the integration of the recognized microfacies and the field criteria of the Khurmala Formation, two facies associations were identified which elucidate deposition in a lagoonal environment including reef patches. Accompanying facies indicate that the formation's sedimentary model is a ramp carbonate platform.