A detailed study of the stratigraphy, sedimentology and thermal history of the Heatherdale Shale, the youngest unit of the Early-Mid Cambrian Normanville Group (Fleurieu Peninsula, South Australia), was undertaken to elucidate its petroleum source rock potential and to collect data crucial to establishing the untested prospectivity of the Stansbury Basin. Stratigraphic and sedimentologic observations made of the upper section of the Normanville Group have delineated potential source beds and enabled reconstruction of their depositional environments. The focus of this study was a typical marine black shale facies, the upper Heatherdale Shale. It is carbonaceous, fissile, pyritic and phosphatic, thus implying anoxic, deep water sedimentation (in 100 metres of water depth) conducive to source rock development. Total organic carbon values in the range 0.73-2.57% (mean = 1.73%) were obtained for the upper Heatherdale Shale, consistent with the presence of potential petroleum source rocks. The thermal maturity of the unit was determined using three maturation indicators. The primary indicator, kerogen H/C atomic ratio, rated the samples as overmature (H/C = 0.22-0.36). However, the carbon isotopic composition of the kerogen (delta 13C PDB = -32.4 to -30.9%) showed no sign of metamorphic alteration. The Methylphenanthrene Index, a particularly useful maturity indicator for sediments deposited prior to the evolution of land plants (ie. pre-Devonian), provided calculated vitrinite reflectance values of 2.50-2.56%. Two offshore locations representing thermal maturation end-member scenarios within the Stansbury Basin were selected for quantitative thermal modelling. A calculated vitrinite reflectance of 2.5% was modelled 15 km NNW of Carrickalinga Head, and a value of 1.2% was used in a second model 20 km E of Kangaroo Island. The above organic geochemical maturation parameters were combined with stratigraphic information and modelled using the BasinMod computer package. Results have shown that liquid hydrocarbons which were expelled by the source rocks between 518 and 500 Ma, if they had somehow since been retained in an unbreached reservoir, would exist today as both oil and gas.