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ABSTRACT: Integration of carbonate sequence stratigraphy, biostratigraphy and depositional system analysis in the Gambier sub-basin, southern Australia

Pollock, Rosalie1, Simon C. Lang2, Brian McGowran2, and Qianyu Li2
(1) National Centre for Petroleum Geology and Geophysics, University of Adelaide, Adelaide, Australia 
(2) University of Adelaide, Adelaide, Australia

The Gambier Sub-basin represents one of the frontier areas in southern Australia with both gas and carbon dioxide fields identified. Sequence stratigraphy based on regional seismic interpretation and sparse well coverage integrated with interpretations of depositional environments, was used as part of the exploration effort in the sub-basin. The ambier Sub-basin (150,000 km2) forms part of a passive continental margin developed during the Jurassic to Tertiary resulting from the separation of Australia and Antarctica. The basin comprises Paleocene-Eocene deltaic clastic sediments, but during the Late Eocene, starvation of clastic sediments led to the deposition of cool-water carbonate platforms and mounds. This process continues today. Seismic data show that these carbonates have clinoformal geometries on the outer shelf, but are punctuated by many incision events. Large submarine canyons are evident on seismic lines probably produced by relative falls in sea level. Mounded structures interpreted as deep-water biogenic carbonate buildups, are similar to those observed on the Eucla Platform over 1000km to the west, and developed during transgressive events. With the aid of biostratigraphy, several high-resolution sequences can be recognised in the Middle Eocene to Middle Miocene section, as part of an overall regressive-transgressive cycle. The development of the carbonate platform is linked to the burial history of the underlying clastic succession (Cretaceous-Eocene). This sequence stratigraphic framework has helped to better understand play concepts in the Gambier Sub-basin.

AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia