Polycyclic aromatic hydrocarbons in ancient sediments and their relationships to palaeoclimate

Combustion-derived and land-plant-derived polycyclic aromatic hydrocarbons (PAHs) have been investigated for an Upper Triassic to Middle Jurassic sedimentary sequence from the Northern Carnarvon Basin, Western Australia. The former included fluoranthene, pyrene, benzofluoranthenes, benzo[e]pyrene and benzo[a]pyrene, and the latter included retene, cadalene and simonellite. Combustion-derived PAHs are most abundant in the Upper Triassic and late Lower Jurassic sediments. The abundances of land-plant-derived markers all maximise in the upper part of the Lower Jurassic section, but vary independently of one another through time. The changes in the relative abundances of these markers have been related to the variation of regional climatic conditions, especially the changes in humidity and seasonality during the Late Triassic to Middle Jurassic times.