Origin of perylene in ancient sediments and its geological significance

The distributions of polycyclic aromatic hydrocarbons (PAHs) in sediments of three Upper Triassic to Middle Jurassic sedimentary sequences from the Northern Carnarvon Basin, Australia have been investigated. Perylene was found to be a major PAH component in the top Lower to base Middle Jurassic sediments that are immature or at low maturity. Its depth/age profiles are not related to the combustion-derived PAHs that have been believed to be produced during ancient vegetation fires before deposition. This suggests a diagenetic origin for perylene. The concentration of perylene in the sediments is proportional to the amount of terrestrial input, decreasing with distance from the source of land sediments. Its carbon isotope composition is slightly heavier than higher-plant derived PAHs, but still in the range of the terrestrially sourced PAHs including higher-plant PAHs and combustion-derived PAHs as suggested previously. Fungi are proposed to be the major precursor carriers for perylene in sediments based on the facts that (1) perylenequinone structures have been previously suggested to be the natural precursors for perylene; (2) perylenequinone pigments exist in many fungal bodies; (3) fungi have played an important role during geological processes.