The Vendian–Riphean section of the Ust’-Maiskaya-366 parametric well was studied. The well is the first deep well drilled in the central part of the Aldan–Maya depression, in the southeast of the Siberian Platform. New probable oil source rocks within the Upper and Middle Riphean deposits have been identified based on core analysis supported by geological-survey data. We make a geochemical description of organic matter from these deposits and report the composition of abundant migrated bitumens discovered in the Ust’-Maiskaya-366 well section. The petroleum content in the Aldan–Maya depression has been predicted with regard to the new geological and geochemical data.