A sequence stratigraphic scheme for the Bight Basin has been developed by Geoscience Australia based on the identification of four megasequences, each related to a different basin phase and their component 2nd-order supersequences.
Basin Phase 1 records the initiation of sedimentation during the Middle-Late Jurassic period of intracontinental extension. Two rift-related depositional units have been identified - the Sea Lion and Minke supersequences. These units consist of fluvial-lacustrine sandstone, siltstone and shale, with minor coal. The extensional phase was followed by a period of slow thermal subsidence throughout most of the Early Cretaceous. Deposition during this time was largely non-marine.
The Berriasian Southern Right Supersequence consists mainly of fluvial-lacustrine sandstone and claystone, while the Valanginian to mid-Albian Bronze Whaler Supersequence is a thick dominantly fine-grained lacustrine succession. Some marine influence is evident within the upper, Aptian-Albian part of the Bronze Whaler Supersequence. An abrupt increase in subsidence rate in the mid-Albian signalled the start of the third basin phase. This period of accelerated subsidence coincided with a period of rising global sea level. This combination of factors resulted in an increase in accommodation, the first major marine flooding event in the basin and the widespread deposition of marine silts and shales of the mid-Albian to early Cenomanian Blue Whale Supersequence.
The present-day distribution of the supersequence indicates that the seaway at that time extended along the southern margin from the open sea in the west. Progradation of deltaic sediments into this seaway (White Pointer Supersequence) commenced in the Cenomanian, following uplift and erosion along the eastern margin of the continent. Deposition was rapid, resulting in the development of overpressure in the underlying marine shales and a short-lived period of shale mobilisation and growth faulting throughout the northern half of the Ceduna Sub-basin. Deposition of the White Pointer Supersequence was followed by the accumulation of the marine-marginal marine mixed clastic sediments of the Turonian-Santonian Tiger Supersequence. Continental break-up in the Late Santonian was followed by a period of thermal subsidence and the establishment of the southern Australian passive margin.
It was during this phase that a second large progradational delta developed, represented by the sand-rich fluvial, deltaic and marine sediments of the Hammerhead Supersequence. A dramatic reduction in sediment supply at the end of the Cretaceous saw the abandonment of deltaic deposition and the development of a cool-water carbonate margin during the Cainozoic.