Background The establishment of a potassium-argon dating laboratory at Amdel was initiated in 1969, with the South Australian Department of Mines providing financial assistance towards the purchase of equipment and continuing operational support in the form of four geochronological projects. Objective The objective of the present Project was to clarify the tectonic and igneous history of south-eastern South Australia during lower Palaeozoic times by the K-Ar dating of granitic and volcanic rocks within and around the margins of the Murray Basin. With the introduction of the rubidium-strontium laboratory in 1970-71, the project was extended so that rocks that were not amenable to K-Ar dating could be analysed by the Rb-Sr technique. Summary of Work Done Almost 200 rocks were examined and petrographic descriptions made between October 1969 and February 1976. During this time, 156 isotopic age determinations were made. Conclusions and Recommendations The main conclusions of this study are: 1. The granitic and volcanic rocks of the south-eastern part of South Australia and the granites of Kangaroo Island and Encounter Bay show a remarkable consistency in age, falling between 460 and 495 Ma. 2. The high initial Sr87: Sr 86 ratios of the Encounter Bay granite and Taratap Adamellite distinguish these granites from the others of the region suggesting a high degree of contamination of the granite magmas by radiogenic Sr-rich crustal rocks. 3. The granitic rocks of the Olary region may be slightly younger than those in the south-east (<460 Ma) while in both areas there are indications of a still younger (~430 Ma), mild, thermal event. An attempt was made to compare the two groups of granites with different initial Sr87: Sr86 ratios with the S- and I- type granites of the Lachlan Geosyncline. However, the paucity of chemical analyses of the South Australian granites prevented any definite conclusions from being drawn. It is recommended that, to test this analogy, a programme of silicate analysis of a representative suite of the Palaeozoic granite samples be undertaken.