oa Extensive Formation of Rearranged Hopanes in the Late Permian, Sydney Basin, Australia

Three series of rearranged hopanes were identified in the late Permian samples from the Sydney Basin, Australia: 18α(H)-neohopanes, 17α(H)-diahopanes, and the early-eluting 9,15-dimethyl-25,27-bisnorhopane homologues. Their relative abundance varies significantly, from absence in the Permian-Triassic mass extinction “dead zone”, to the C30*/C30 αβ hopane ratio reaching 93 in samples from the Illawarra Coal Measures. Samples from the Tongarra Coal Measures at Austinmer Beach contain the highest abundance of rearranged hopanes. Dependencies and correlation between three series of rearranged hopanes and monomethylalkanes, steranes, tricyclic terpanes and various aromatic compounds have been analysed. The rearrangement process was triggered and controlled by a combination of factors, including the presence of terrigenous organic matter, deposition under fresh water sub-oxic conditions, volcanic activity that provided the nutrients for enhanced cyanobacterial activity, and possibly the presence of particular trace elements.