The stratigraphic sequence in the Slacks Creek area consists of low-grade metamorphics of the Lower Palaeozoic Neranleigh-Femvale "Group", Triassic sediments of the Tingalpa and Moorooka Formations, minor sediments and volcanics of possible Tertiary age, Tertiary soils, and Quaternary sediments and soils. The Neranleigh-Femvale "Group" is composed of metaquartzite, greywacke, and minor phyllite; the Tingalpa Formation of partly calcareous shales and sandstones; the Moorooka Formation of conglomerate, shale and sandstone. Volcanic mud balls at the base of the Tingalpa Formation may indicate equivalence of the base of this formation in the Slacks Creek area to the Brisbane Tuff. Megafossils from the Tingalpa and Moorooka Formations have a Lower Mesozoic aspect. Palynological evidence obtained suggests an Upper Triassic age for the Tingalpa and Moorooka Formations, The Tingalpa Formation unconformably overlies the Neranleigh-Femvale "Group" and is succeeded unconformably by the Moorooka Formation which is in tum overlain unconformably by Cainozoic sediments. Earth movements involving slight displacements of the Palaeozoic basement blocks apparently occurred during the Triassic. Geomorphology in the area is strongly controlled by the joint pattern; the effects of relative hardness of rock types, attitude of beds, changes in climate, and relative changes in sea level are also evident.