Samples from the Paleocene-Oligocene Pabdeh Formation were evaluated in 11 different oilfields located in the south ‎Dezful Embayment using bulk rock pyrolysis and organic petrographic methods. The combined application of these ‎techniques provided new insights about organic geochemistry and paleo-depositional settings of the Pabdeh Formation. ‎Results from this study suggest that the Pabdeh Formation is highly heterogeneous in terms of its organofacies properties. ‎In some of the studied oilfields the Pabdeh Formation is characterized with a highly organic-rich facies that is sandwiched ‎between two organic-poor facies. The mentioned organic-rich facies is highly variable in terms of it thickness and ‎therefore the Pabdeh Formation is entirely composed of organic-lean platform carbonates in some other oilfields. Organic ‎petrographic investigations of the organic-rich facies confirm the presence of abundant amorphous organic matter ‎preserved under highly reducing paleo-depositional conditions. The organic matter becomes thermally transformed into ‎hydrocarbons in deeply buried regions, thereby contributing petroleum (migrabitumen) into the overlying organic-poor ‎facies. These zones are defined as the “impregnated facies” for the first time in this study. The identification and mapping ‎of the organic-rich versus impregnated facies can be a critical risk factor for petroleum system analysis in the Cenozoic ‎succession and can open a new window for unconventional resource exploration in the frontier Pabdeh Formation of the ‎Zagros basin.‎