An optimised stepwise alkaline permanganate degradation was shown to have potentials in elucidating the genesis pathway and the origin of kerogens, and, more specifically, to reveal preserved precursors in a kerogen matrix. Thus, Pumpherston shale kerogen, used as the substrate in this study, was found to be of mixed origin, i.e., to contain both inherited resistant algal structures (B. braunii A and B algaenans), as well as resistant biomacromolecular components of continental flora (cutans). It is suggested that this kerogen or parts of it were formed by the selective preservation pathway