This company study of the Eromanga Basin sequence within PELs 5 and 6 and ATP 259P was designed to provide the Delhi Petroleum exploration consortium with data on the following: (a) thickness and correlation of Aptian-Albian units throughout the licence areas: (b) timing of structural movements; (c) the nature and distribution of the Toolebuc Formation; (d) the relationship between Aptian-Albian glauconitic sandstones in the southern Cooper Basin area and the Toolebuc Formation gamma ray anomaly elsewhere: (e) the hydrocarbon potential of the section above the 'C'-Horizon. The study was stimulated by minor but significant hydrocarbon shows in Toolebuc Formation organic shales in Queensland, and by oil shows and non-commercial gas recoveries from glauconitic sands occurring at a similar level in South Australia (e.g. the Coorikiana Sandstone at the Strzelecki Prospect). It is intended that the basic geological data on the Cretaceous synthesised by this report be applied in other studies addressing stratigraphic, sedimentological, structural and seismic predictive models useful in the search for Mesozoic hydrocarbons.