An oily liquid and several types of bitumen were found in the silicified porous carbonate-rich Looking Glass Formation, in a BMR stratigraphic hole drilled in the Proterozoic McArthur Basin in 1979. The bitumen is accompanied by sulphides (including pyrite, chalcopyrite, and marcasite), and has been trapped beneath a thin claystone which is present at the unconformity at the base of the Balbirini Dolomite. It is thought to be a residue from oil generated lower in the McArthur Group or in the Tawallah Group and then trapped in the Beetle Spring Anticline. Proterozoic strata as old as the McArthur Group (ca. 1600 m.y.) should not be overlooked in the search for hydrocarbons in Australia.