--> ABSTRACT: Tectonics and Hydrocarbons in Bass Strait, SE Australia, by Kathy A. Hill, Kevin C. Hill, and Mark A. Smith; #91019 (1996)

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Tectonics and Hydrocarbons in Bass Strait, SE Australia

Kathy A. Hill, Kevin C. Hill, and Mark A. Smith

The hydrocarbon-rich Gippsland, Bass and Otway basins of Bass Strait were initiated by Neocomian N-S rifting of Australia from Antarctica, their architecture strongly influenced by Paleozoic basement fabric. In the Aptian- Albian, the rift received approximately ~106 cubic km3 volcaniclastic sediment from the inferred arc along Gondwana's Pacific margin. In distal areas, terrestrial source rocks accumulated, productive in the Otway Basin. Global plate realignment induced mid-Cretaceous break-up, passing south of Tasmania, creating successor basins, the Gippsland aulacogen, Bass failed rift and Otway passive margin. Mid Cretaceous uplift around the failed rift supplied quartzose (reservoir) sediment to the Otway and Gippsland basins, funnelling sedime t into the aulacogen in the post-rift. Starved Otway inter-delta and Gippsland/Bass lacustine and delta plain sediments developed hydrocarbon source rocks that generated during Tertiary burial. The Gippsland aulacogen, formed during Late Cretaceous Tasman Sea spreading, is primarily extensional in nature and not a strike-slip basin, with traps created by minor Tertiary inversion. Despite large oil discoveries in the 1960s, the tectonics of the Gippsland Basin remain poorly understood and need to be tied into the Mesozoic evolution of Gondwana's Pacific margin. Continued prospectivty of Bass Strait is illustrated by the Minerva gas discoveries in the Otway Basin and the recent probable approximate ~3001 gross oil column in the Turrum structure in the Gippsland Basin. Critical t future success is understanding the regional tectonics and imaging below Tertiary carbonates.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California