The Lorne Basin is a small, intramontane, Triassic basin, surrounded by the New England Fold Belt. Located between Taree and Port Macquarie, the basin is composed of northern and southern segments separated by an outcrop of basement forming a faulted ridge. The overall dimensions of the basin are approximately 20 km in an east-west direction and 35 km in a north-south direction. It probably extends offshore under the continental shelf, but this is speculative. Although situated between two major sedimentary basins (the Sydney Basin and Clarence-Moreton Basins), the Lorne Basin has no direct connection with either of them.
The basin is filled with Early Triassic continental sediments of the Camden Haven Group. Terrestrial sedimentation into this basin was probably initiated by tectonic activity along surrounding major faults and serpentinite belts. The sediments include alluvial fan deposits of the Laurieton Conglomerate, associated desert plain or playa deposits of the Camden Head Siltstone and overlying fluvial sediments of the Grants Head Formation. Lorne Basin rocks are overlain by minor Cainozoic volcanics and intruded by Cainozoic microgranites.
The thin sedimentary section of terrestrial lithologies has no potential source rocks and is intruded by Cainozoic microgranites. Fluvial channel sandstones within the Grants Head Formation could be considered as potential reservoir rocks, but the sealing quality of associated intraformational siltstone is dubious. The onshore basin has no petroleum prospectivity. The thickness of any possible offshore extension is unknown, but on the available onshore evidence its prospectivity is probably very low.