The Upper Cretaceous source rocks of Jordan are organic-rich carbonate mudrocks that represent excellent source rocks but are essentially still immature to just entering the oil window. Therefore, they offer a unique opportunity to study lithology, source rock composition, and geochemistry prior to the onset of maturation and expulsion of hydrocarbons. Our study aims to examine the lithological and geochemical characteristics of these high-quality source rocks. The study utilizes an integrated petrographic and geochemical approach to define the different microfacies in the studied source rock sequence and understand their intrinsic variability.