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Petrographic and Biostratigraphic Study on a Representative Core Section From the Kurdistan Region of Iraq

Abstract

It is estimated that the Zagros fold and thrust belt in the Kurdistan Region of northern Iraq may contain up to 45 billion barrels of oil. However, the fold and thrust belt in the Iraqi Kurdistan has received very limited geological attention in the past decades. During the Cretaceous the area was affected by intense tectonism due to the collision of Arabian and Iranian plates. The depositional history of the studied area is characterized by a pre-drowning phase of reefal/lagoonal dolomitic limestone represented by Qamchuqa Formation (Early Cretaceous); a transitional phase; and a post-drowning phase of sedimentation with the deposition of the deep water facies of the Kometan Formation (Late Cretaceous - Turonian-Santonian) (Bellen et al., 1959; Buday, 1980). In the past few years, Oryx Petroleum has been the operator of the Hawler License area, drilling several wells in the Demir Dagh, Banan and Zey Gawra fields. In this study we discuss the results of a multi-proxy approach (petrography, calcareous nannoplankton and foraminifera) carried out on a 27 meter core from Oryx Well Demir Dagh 11 (Erbil, Iraqi Kurdistan, NE Iraq). Data was used to produce a biostratigraphic age model, to refine paleoenvironmental reconstructions, and to describe the petrography of the samples, with emphasis on porosity and mineralogy. Preliminary results show that the samples from this well belong to three Cretaceous formations which have distinct sedimentary and diagenetic characteristics: bioclastic grainstones/packstones from the Upper Kometan Formation, and calcareous and crystalline dolostones from the Lower Kometan and Upper Qamchuqa Formations. The Biostratigraphic analysis is ongoing but preliminary results are promising. Integrated datasets from the nannofossil and foraminifera faunas, as well as the petrographic studies would improve the knowledge about timing of the complex paleoenvironments evolution in the tectonically active collision area of Northern Iraq during the Cretaceous, an area nowadays not well understood by international researchers but of major interest for oil companies. References: Bellen, R.C. Van, Dunnington, H.V., Wetzel, R. Morton. D. (1959): Lexique Stratigraphique International. Asie, Iraq, 3, 333 pp. Buday, T. (1980): Stratigraphy and paleogeography, in: Kassab, I.I.M. and Jassim, S.Z. (eds.): The regional geology of Iraq (D.G. Geol. Surv. Min. Invest.), Baghdad, 1, 445 pp.