The Madigan Inlet Member of the Kanmantoo Group at Carrickalinga Head and Myponga contains angular clasts of quartz, fresh feldspar and muscovite, altered feldspar and a range of lithic grains in a micaceous matrix. Grain sizes are unsorted below 0.2 mm but only a few grains over this size are included. However, these consist of rounded clasts of quartz and shale up to 1.5 mm and angular shale fragments several centimetres across. Weak traces of bedding are sometimes distorted. Framework and trace minerals indicate a source where plutonic and metamorphic rocks were exposed. The Campana Creek Member at Blowhole Creek is a mature but thermally altered sediment consisting almost exclusively of quartz and biotite except at one point in the sampled section where garnet and actinolite occur as porphyroblasts. The top of the member may be transitional to the Backstairs Passage Formation.