Clastic petrofacies, provenance and organic facies of the Bozbel Formation (Lutetian) in the eastern Sivas Basin (Turkey)
The Bozbel Formation (Lutetian) of the eastern part of the Sivas Basin, central Anatolia, Turkey, displays a range of lithofacies which vary greatly in thickness. The formation consists of conglomerates, sandstones, mudstones and shales, marls, limestones, and sandy limestones, clayey limestones, tuffites, and volcanic breccias. The aim of this study is to determine the elastic petrofacies of the sandstones and to describe the characteristics of the organic facies and source rocks present in the Bozbel formation. The sandstones can be classified essentially as arkoses, lithic arkoses and feldspathic litharenites, cement-rich and containing minor amounts of olivine, pyroxene, chlorite, biotite, muscovite and opaque minerals. These sands were derived from magmatic are and mixed provenances. The source-rock characters of the finer-grained Bozbel rocks and their organic facies have been determined by means of total organic carbon (T.O.C.) analyses, rock-eval pyrolysis, vitrinite reflectance data and clay mineral paragenesis, together with illite crystallinity values. The organic matter content is dominated by type 3 kerogen. Illite crystallinity indices and vitrinite reflectance data run parallel with each other and are consistent with the catagenetic stage of organic matter evolution. The Bozbel Formation in the south Hafik region is appropriately mature to yield hydrocarbons, but because of the generally low content of organic matter it is unlikely to have generated petroleum but is known to be gas prone. (C) 1996 Elsevier Science Ltd.