Field geological mapping of an 800 square mile area located immediately north-west of the Tarcoola Goldfield was carried out at a scale of approximately 1:84,480 (3/4 inch = 1 mile). A continuation of the regional geology from previously mapped areas on SML 436 to the south and east was found, the main difference being the occurrence of large areas of Gawler Range Volcanics. Evidence of three separate tectonic events was discerned in the fabric of the rocks examined. Possible erosion of the Tarcoola Beds in one locality was interpreted. Two phases of granite intrusion are also postulated, one taking place prior to or at the beginning of the volcanic event, and the other during its waning stages or perhaps even later on.