Publication Name: Eastern Australian Basins Symposium 2001
Authors: J.B. Willcox and J. Sayers
Date Published: November 2001
Number of Pages: 35
Reference Type: Magazine Article
Abstract:
The Gower Basin is the principal depocentre within the 'Central Rift Zone' of the Lord Howe Rise (LHR). It lies within the Australian Exclusive Economic Zone, between Lord Howe Island and a region of planated basement ('Lord Howe Platform ') that makes up the eastern half of the rise. In pre-drift reconstructions, the southern part of the Gower Basin is aligned with the northern edge of the Gippsland Basin, and the two basins probably shared a similar history until breakup in the Campanian ( -84 Ma).The Gower Basin has not been penetrated by drilling, however, the limited seismic available indicates that it formed by oblique extension, with later inversion and shortening. It comprises a series of NNW-trending horsts/grabens offset by NE-trending accommodation zones. The sediment fill averages 1,500- 3,000 m but reaches a maximum of over 4,000 m.
Two syn-rift phases are recognised that bear analogy to the Cretaceous Otway/Strzelecki and early Golden Beach Groups in the Durroon Sub-basin and Gippsland Basin. Post-breakup depositional environments are interpreted as initially coastal plain to restricted marine, but becoming marine from about the Paleocene. Diapir-like features seem to emanate from the syn-rift section along the axial zone of the main graben, and could be mobilised shale or possibly salt.
The structural history of the basin has given rise to a plethora of potential petroleum traps, including rift-margin structures, syn-rift folds and inversion structures, pinchouts, possible diapirs and buildups.
In terms of petroleum prospectivity, the greatest uncertainty is the thermal maturity of potential source beds that have only moderate overburden. Positive evidence for the active generation and migration of hydrocarbons comes from the adjacent Fairway, Middleton and Monawai Basins, where 'bottom simulating reflectors ' and 'flat spots' have been recognised. It is concluded that the Gower Basin offers a reasonable opportunity for petroleum exploration in a deepwater, frontier setting.