Upper Cenomanian-Lower Campanian Derdere and Karababa formations in the Çemberlitaş oil field, southeastern Turkey: their microfacies analyses, depositional environments, and sequence stratigraphy

Abstract

The frontal belt of the southeastern Anatolia fold-thrust belt in Turkey contains several small to mid-size oilfields, producingfrom carbonate reservoirs of the Cretaceous Mardin group. Many of these fields are found along narrow, asymmetrical anticlinalstructures, associated with the formation of the fold-thrust belt. The Çemberlitaş oil field in Adıyaman, southeastern Turkey, is oneof the most important oilfields in the region. It produces from the Upper Cretaceous Derdere and Karababa formations of the Mardingroup. We have conducted a detailed study of the microfacies, depositional environments, and sequence stratigraphy of the Karababa(Coniacian-lower Campanian) and Derdere (mid-Cenomanian-Turonian) formations in the oil field. Eight microfacies in the Karababaand Derdere formations have been identified; the microfacies in the Karababa formation are 1) mollusk-echinoid wackestone/packstone,2) dolomitic planktonic foraminifera wackestone, 3) planktonic foraminifera bearing wackestone/packstone, and 4) phosphatic- glauconitic planktonic foraminifera bearing wackestone. The microfacies in the Derdere formation are 5) lime mudstone, 6) bioclasticwackestone/packstone, 7) medium-coarse crystalline dolomite, and 8) fine crystalline dolomite. These microfacies suggest that theDerdere formation was deposited in lagoonal to shelf depositional environments and the Karababa formation was deposited in a deepto shallow marine intrashelf basin. Two third-order sequence boundaries of late Turonian and early Campanian in age have beenrecognized in the reservoir interval. Depositional sequences contain transgressive and highstand systems tracts. These sequences arecompared with those in other regions to differentiate the local, regional, and global factors that controlled sedimentation within theÇemberlitaş oil field area.