Organic geochemistry and depositional environment of the Aptian bituminous limestone in the Kale Gümüşhane area (NE-Turkey): An example of lacustrine deposits on the platform carbonate sequence

► Aptian bituminous limestone is located in the upper part of this carbonate sequence. ► Bituminous limestones were deposited in a suboxic-freshwater lacustrine environment. ► Bituminous limestones contain algal and terrestrial organic matter. ► The maturity data indicate early mature-mature character of bituminous limestone. ► Bituminous limestones are considered to have generated some amount of oil and gas.