Identification of carotane breakdown products in the 1.64 billion year old Barney Creek Formation, McArthur Basin, northern Australia

Some of the oldest, indisputably indigenous, and thermally exceptionally well preserved biomarkers occur in the uppermost sections of the 1.64 billion year old (Ga) Barney Creek Formation (BCF) of the McArthur Basin in northern Australia. These rocks preserve more than 22 different C40 carotenoid derivatives, including the saturated hydrocarbons β-carotane, γ-carotane and lycopane. However, in deeper sections of the BCF, saturated carotenoid derivatives were not detected. To determine whether their absence from the deeper sections is a primary biological phenomenon or the result of degradation, we simulated the catagenesis of β-carotane in the laboratory by way of hydrous pyrolysis. Using breakdown products as elution standards, we were able to confirm the presence of β- or γ-carotane derivatives in the deeper sections, where the C40 parent compounds had been degraded.