A regional geological survey covered 15 standard 1-mile map sheets. Detailed mapping established a 50 000 ft sequence of Archaean sedimentation of gneissose, schistose and granitoid rocks, migmatite, quartzite, dolomite and haematitic quartzite. These rocks have undergone intense metamorphism and deformed by compression and folding. Younger sediments include ?Cambrian shelf deposits, Tertiary marine limestone, Pleistocene aeolinite and Recent alluvium and sand dunes. Economic mineral deposits which are all described, are confined to the Archaean belts and include copper, silver, lead, manganese, talc, asbestos, graphite and magnesite. Ferruginous quartzite and chert are thin and low grade, and offer no source of iron ore. The aeolianites are important aquifers and supply potable water at Uley.