P/Tr Sediments from the Perth Basin: Implications for Petroleum Source-Rock Formation

An oil-source rock correlation has been established for the northern onshore Perth Basin ( Western Australia) based on biomarkers attributed to a green sulphur bacterial source. These biomarkers have been identified throughout the entire Sapropelic Interval of a proven petroleum source rock intersected within a recently discovered marine Permian-Triassic Perth Basin borehole (Hovea-3) and several Perth Basin crude oils (Thomas et al., 2004, Australian Journal of Earth Sciences 51 , 423-431 ). The presence of photosynthetic pigments and carotenoids of green sulphur bacteria , or their diagenetic alteration products in sediments provide unequivocal evidence for photic zone euxinic conditions in the paleowater column. Photic zone euxinia is usually associated with the widespread deposition of organic-matter-rich sediments that constitute important source rocks for petroleum deposits that are being exploited today. With the exception of the Perth Basin, s uch organic-matter-rich sediments are virtually absent from Upper Permian and Lower Triassic sediments globally. Several lines of evidence indicate localised surface ocean productivity may have played a key role in the deposition of a petroleum source rock at this location, although photic zone euxinia was globally more widespread during the Permian-Triassic Superanoxic Event.

Personnel

K. Grice, W. Dunning, S. Wang, R.E. Summons, E. Grosjean, R. Twitchett, M. Böttcher

Funding

ARC (QEII), MIT was supported by the NASA Exobiology grant NAG5-1236.

Collaborators

Origin Energy, Geoscience Australia, MIT ( USA), Max Planck Institute for Marine Microbiology ( Germany) ,