Sequence stratigraphy of the Bowen-Gunnedah and Surat Basins in New South Wales

A new tectonostratigraphic framework for the southern Bowen, Gunnedah and Surat Basins in New South Wales is developed, based on the sequence stratigraphic and structural interpretation of regional reflection-seismic data, and petroleum and stratigraphic wells. This framework provides an improved correlation between the Bowen and Gunnedah Basins, and delineates the relationship between tectonic events, basin phases, and the development of depositional sequences. The Early Permian-Cretaceous depositional history of the basins in this region was controlled by successive phases of tectonic subsidence driven by extension, thermal relaxation and lithospheric flexure, interrupted by periods of contraction and uplift. Early Permian extension was characterised by the eruption of volcanic rocks and the accumulation of dominantly lacustrine sediments, followed by the deposition of thick coal-conglomerate successions, particularly along the eastern margin of the basin. The succeeding thermal subsidence phase was quickly overwhelmed by flexural subsidence driven by foreland loading during the Early-Late Permian, and the deposition of marine, deltaic and non-marine rocks. Late Permian contraction and uplift in the Gunnedah Basin was followed by the accumulation of non-marine Triassic rocks derived from the New England Orogen. A dominantly fluvial Middle Triassic succession is present across the entire region. Effects of the Middle-Late Triassic contractional event that is evident throughout the Bowen-Gunnedah-Sydney basin system were concentrated along the basin-bounding Goondiwindi, Kelvin and Mooki Faults and also adjacent to the Boggabri Ridge.