Impacts of natural irradiation on sedimentary organic matter–A review

•Radiolytic changes in terrestrial OM are predominately caused by γ-radiation.•In situ radiolysis of oil provides a potential chronometer for oil residence time.•Radiation interplays with thermal force and may boost hydrocarbon generation.•OM radiolysis is an alternative explanation for abnormal natural gas signatures.•Radiolysis of sedimentary OM is more complex than previously thought.