The Karoo Supergroup is the largest stratigraphic unit in Southern Africa, covering almost two thirds of the present land surface, including central Cape Province, almost all of Orange Free State, western Natal, much of south-east Transvaal, Zambia, Zimbabwe and Malawi. The Karoo Supergroup is divided into the following strata (from oldest to youngest): * Dwyka Group (glacial marine) * Ecca Group * Beaufort Group (terrestrial) * Stormberg Group (including basalts)