The article is devoted to the role of algal material of the Bazhenov suite in the the formation of authigenic dolomite. Authigenic dolomite could form in the environment of convergence of two processes: hydrothermal («wedging out» in the rear zones) and catagenetic (background) generated by conductive heat transfer. The development of the algal dolomite in situ shows that the source rocks experienced the stage of intensive (final) hydrocarbons generation.