The Clare 1-mile mapsheet area is situated about 70 miles north of Adelaide, South Australia, in partly hilly agricultural and pastoral country. The oldest Adelaide System (Proterozoic) rocks are the phyllites, quartzites and dolomites of the River Wakefield Group, overlain by the Burra and Umberatana groups. This last group contains the Mintaro Shale, from which high-quality flagstone is obtained near Mintaro, besides the Appila Tillite and the Tapley Hill Formation, which is the youngest Precambrian formation exposed. The Precambrian is faulted and tightly folded in four main north-south anticlinal zones, with intervening more open synclinal areas. The north-northwest trending Alma Fault escarpment forms the boundary between the Clare hills and the Kybunga plains to the south-west. Younger deposits include Tertiary gravels and duricrust, and Recent outwash, soils and creek and claypan alluvium.