The Hillsborough Basin straddles the east coast of Queensland, north of Mackay. The basin covers 2700 km2, most of which lies offshore in water depths up to 20 metres. The Hillsborough Basin contains up to 1250 metres of Paleogene sediments overlying Late Devonian to Early Carboniferous sediments and volcanics onshore, but on seismic evidence may reach a thickness of up to 3000 metres offshore. The Hillsborough Basin is one of four structural blocks in the Proserpine area, along with the Midgeton Block to the west and possibly southeast, the Airlie Block in the northeast and the Whitsunday Block in the east.
The Hillsborough Basin developed as a narrow southeast trending asymmetrical graben on the eastern side of the Midgeton Block during a phase of Late Cretaceous or Paleogene faulting. Sediments accumulated in the graben during the Paleogene: and the thickest known section is offshore along the northeast margin of the basin. The sedimentary fill (Cape Hillsborough beds) is largely composed of sandstone, mudstone and minor conglomerate: the depositional environment was probably entirely non-marine. Oligocene volcanic flows and intrusions are present in the south of the basin at Cape Hillsborough, an onshore horst feature. The stratigraphy of the offshore Hillsborough Basin is largely unknown as there are no wells and only poor quality seismic data. Oil shale and lignite are present within the Cape Hillsborough beds, including the Condor Oil Shale deposit, located to the south of Proserpine in the northwestern part of the basin. The offshore part of the Hillsborough Basin lies entirely within the Great Barrier Reef Marine Park, in which petroleum exploration is prohibited.