Paleogene rocks comprising the Paleocene-Eocene boundary in the Bolu basin show different characteristics of organic material type and metal enrichment. The dark gray-dark brown-black bituminous rocks of the Ozankoy (Ankara) field that was selected to compare its bituminous rock features with the Pazarkoy-Mengen, Gokcesu, Guneytepe, and Himmetolu fields in the Bolu basin have organic carbon values averaging between 4.74 and 28.29%. This type of rocks, compared to rock units with high organic carbon contents, are formed in different paleogeographic, paleoclimate, and geochemical conditions. Production and abundance of living organisms in oxygenated and nutritious seawater are much higher. Dissolved oxygen and nutrients decreasing in seawater in the following seasons together with anaerobic bacteria and temperature are the major factors for dying, accumulation, and fossilization of organisms. In the Bolu basin, determination of formation temperature of the Paleogene rocks is very important for evaluation of organic material enrichment in deposits. The absolute temperature of the depositions cogenetic with OM enrichment in the Paleogene rocks of the Bolu basin was first determined in the present study. In determination of temperatures of organic material and deposition, the empirical formula of [To = 28 (A/15B)] was applied with the use of Ca/mg ratios. The average deposition temperatures of OM-rich sediments in various parts of the Bolu basin are as follows: 25.5C (Pazarkoy-Mengen), 27C (Gokcesu), 26.5C (Guneytepe), 27.7C (Ozankoy-Ankara), and 27.0C (Himmetolu, Miocene). As shown, deposition of OM-rich sediments takes place under hot climate conditions regardless of space and time. Temperatures obtained from recent sapropelic deposits (22C-25C-27C; Holocene, Eastern Mediterranean region) are found to be comparable with temperatures from Paleogene and also Miocene bitumen-rich rocks.