The Late Jurassic-Cainozoic Gippsland Basin is a large basin on the southeast margin of Australia's continental shelf offshore Victoria. The basin is one of Australia's most prolific and mature petroleum provinces, but oil production has waned since the 1980s.
About two thirds of the basin lies offshore in mainly shallow water (<200 metres), although in the Bass Canyon in the east, water depths exceed 3000 metres. The basin overlies Palaeozoic metasediments and consists of a central depocentre (the Central Deep) with up to 10 km of section, flanked by the North and South Strzelecki Terraces, in turn flanked by the North and South Platforms. Initial rifting in the Early Cretaceous resulted in a complex system of graben and half-graben, forming part of the southern rift system between Australia and Antarctica. Volcanogenic and non-marine sediments up to 3000 metres thick were deposited during this phase (Strzelecki Group).
Renewed extension in the Turonian-Campanian, associated with the opening of the Tasman Sea, established the Central Deep as the main depocentre. Coarse-grained alluvial and fluvio-lacustrine facies were deposited during this phase (lower Latrobe Group), with minor marine incursions from the late Santonian. Post rift subsidence was accompanied by alternating marine and non-marine fluvio-deltaic/alluvial deposition in the Late Cretaceous-Palaeogene (upper Latrobe Group). Major canyon cutting and subsequent canyon-fill deposition occurred in the Eocene. Cool-water marine carbonate sedimentation commenced in the Early Oligocene (Seaspray Group) and progradation of the carbonate shelf continues today. Middle Miocene compression formed a series of NE to ENE-trending anticlines that host many of the basin's large oil and gas accumulations.
The hydrocarbons are predominantly sourced from non-marine facies of the upper Latrobe Group, but marine source rocks are also locally present. Marine barrier and shoreface sandstones, particularly those at or near the top Latrobe level, provide the best quality reservoirs.