The Middle Oligocene-Lower Miocene deltaic sediments of the Osmancik and Danisment Formations in NW Turkey comprise organic matter-rich shales and coals. The shales and coals have a mostly very good source rock potential due to its total organic carbon content ranging from 0.02 to 45.53%. T-max (pyrolysis temperature at the maximum rate of kerogen conversion) values have been measured between 351 and 449 degrees C. Thus, the sediments are ranging from immature (only biogenic gas) to middle mature. In addition, organic petrographic investigations in this study suggest that organic matter content of the coals and shales are made up of amorphous (0-5%), herbaceous (3-15%), woody (75-95%), and coaly (0-15%).