Thermal maturities and inferred palaeoenvironments of hydrocarbons from the southern Sydney Basin

The Shoalhaven Group in the southern Sydney Basin contains an extensive sedimentary record of the Permian period. Regional thermal maturity and palaeoenvironments have been interpreted using hydrocarbons primarily from drillcore DM Callala DDH1, Jervis Bay. Palaeoenvironmental interpretation is largely inhibited by thermal maturity in the Shoalhaven Group, with calculated vitrinite reectance values associated with the wet gas condensate window. These high thermal maturities are attributed to the large volume of overburden deposited above the Shoalhaven Group during the Mesozoic. Wildfire-associated polycyclic aromatic hydrocarbons have been used in place of more common biomarkers, and indicate relative changes from cooler climates in the early Permian to warmer, more temperate climates in the mid Permian and probable cool, dry climate in the mid to late Permian. Relative proportions of dibenzothiophene to fluorene are recommended as indicators of source input for high thermal maturity organic matter, as data preferentially clustered by formation and expected source input.