Mapping of the Wooltana Volcanic Belt in the northern Flinders Ranges of South Australia has shown that 2000 feet of Willouran trachytic lavas, with minor andesites and rhyolites, outcrop along the southern margin of the Mount Painter complex and extend southwards along the eastern boundary of the ranges, to 2 miles beyond Wooltana Homestead. They are overlain by Torrensian to Sturtian glacial beds. The area has been bisected by a steep reverse fault (Paralana Fault) system, and associated splintering and wrench faulting is combined with tight folding in the north and west. The northern part of the area is regionally metamorphosed. Copper and asbestos mineralisation is widespread. Gold, uranium and beryllium also occur. Comparison with other recorded Precambrian volcanics in South Australia, both in situ and diapirically emplaced, suggests that the original area of extrusion exceeded 30,000 square miles. A general comparison is made with volcanics similar in age and type elsewhere in Australia. A suggested possible common origin with the Gawler Range Porphyry and Moonta Porphyry in South Australia is discussed. The mineralisation of the Adelaide System sediments is suggested to be exhalative-sedimentary in type.