--> Abstract: Tectonic Controls on the Development of Lacustrine Systems, Bass Basin, Australia, by Jane E. Blevin, Alan D. Partridge, Chris J. Boreham, and Simon C. Lang; #90039 (2005)

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Tectonic Controls on the Development of Lacustrine Systems, Bass Basin, Australia

Jane E. Blevin1, Alan D. Partridge2, Chris J. Boreham1, and Simon C. Lang3
1 Geoscience Australia, Canberra ACT, Australia
2 Biostrata Pty Ltd, Melbourne, Australia
3 University of Adelaide, South Australia, Australia

The Bass Basin (offshore southeast Australia) is an intracratonic rift basin that contains a largely terrestrial succession of Early Cretaceous to Late Tertiary sediments and proven hydrocarbon accumulations. Geochemical correlations between oils and potential source rocks demonstrate that Paleocene to Early Eocene coals have sourced the condensates and gases. An integrated basin analysis study has identified six basin phases and related megasequences/supersequences. These sequences correlate to three periods of extension and three subsidence phases. The multiple phases of extension resulted in a strongly compartmentalized basin architecture dominated by interlinked northeast- and southwest-dipping half graben. Lacustrine systems developed within the discrete depocentres during the latter stage of rifting and during the early subsidence phases. Peat mires developed along the margins of the lakes but were most prolific during the Late Cretaceous (Maastrichtian) to early Middle Eocene as waning subsidence rates signaled a balance between accommodation, sediment supply and peat production. Three lacustrine cycles have been identified and correlated to the following tectonic events: 1) Turonian to Coniacian, Durroon Rift Phase, discrete deep half graben, high accommodation rates and increased sediment supply; 2) Maastrichtian to Early Eocene, Bass Rift Phase, interlinked shallow half-graben, waning accommodation rates and moderate sediment supply; and 3) Middle Eocene (Subsidence Phases 1 and 2), post-rift, broad low relief and compaction-controlled depocentres, moderate sediment supply and high base level Seismic mapping of the coaly facies in the Bass Megasequence, together with modelling of generation and expulsion, has shown areas of higher prospectivity and potential migration pathways.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005