Organic geochemistry characterictics, depositional environments and hydrocarbon potential of bituminuous shales in Northwest Anatolia

Organic Geochemistry Characteristics, Depositional Environments and Hydrocarbons Potantial of Bituminuous Shales in Northwest Anatolia In this study, organic geochemical characteristics of the Tertiary aged bituminuous shales in Beypazarı, Seyitömer, Himmetoğlu, Hatıldağ, Gölpazan and Bahçecik areas (NW Anatolia) have been examined. The bituminuous shales in all the studied areas have signficantly high TOC values. In general, they are typical with high HI and low 01 values. Pyrolysis/TOC analysis results indicate that Beypazarı, Himmetoğlu, Gölpazan and Bahçecik shales contain only Type I kerogen. Seyitömer and Hatıldağ, however, minor amounts of Type II kerogen in addition to Type I kerogen. Tmax values for these shales indicate that they are all immature and haven't generated petroleum. Gas chromatograms of Himmetoğlu, Hatıldağ, Gölpazan and Bahçecik shales show a bimodal distrubition dominated with low number n-alkanes. Such a distrubition indicates that these shales are composed predominantly of algea and minor amounts of terrestrial organic matter. Pr/Ph ratios of the shales suggest that an anoxic depositional environment for the Beypazan, Seyitömer and Hatıldağ shales, and a suboxic environment for the Himmetoğlu, Gölpazan and Bahçecik shales deposited. The biomarker parameters calculated using m/z 217 and m/z 191 mass chromatograms obtained by GC-MS analysis indicate that the bituminuous shales include immature organic matter. Gammacerane, a typical biomarker for saline depositional environment, has ben determined for all shales except those from the Beypazan area. When other biomarker parameters are taken in to account, it is apparent that all shales deposited in saline environments. In general, the data gained, indicate lacustrine depositional environments for the shales in all the studied areas. However, trace amounts of C30 sterane found in only shales from the Seytiömer area indicate marine input and suggest lacustrine depositional environment that was occasionally inundated by the sea. In general, The shales studied in this research have not reached the degree of maturation to be able to generate hydrocarbon. Key Words: Bituminuous Shale, NW Anatolia, TOC, Kerogen, Maturation, n-alkane, Biomarker, GC, GC-MS IX