Abstract: The aim of this study is to indicate the organic geochemical characteristics of the Lower Miocene limestones. The Yazırformation contains various lithological and biofacies deposits. These are, from bottom to top, the coarse grained elastics,clayey limestones with laminated algae and miliolid, thick bedded limestones with algae and corals, clayey to sandylimestones with benthic foraminiferaThe total organic carbon content of Yazır formation is poor, but in some levels, it seems to be rich. Rare hydrocarbonoccurrences are also seen in these sections. Samples are derived from the marine organic matters (amorphous) in general.Vitrinite reflectance values range between %0.12-0.44. When these data is considered, the Yazır formation is thought to be ina diagenesis stage. When all the data are evaluated together, the Yazır formation can be regarded as a source rock for oil atsome levels. Organic geochemical and microscopic data show B organic facies according to Jones (1987) and Baskin (1997)classifications.