Vredefort, South Africa

The Vredefort structure (or Vredefort Dome) is situated about 120 km SW of Johannesburg and consists of a central core of mainly uplifted crystalline basement with a diameter of about 45 km. About three fourths of the core are surrounded by a ≤60-km-wide collar, which is formed by a series of upturned and overturned strata including metasedimentary and metavolcanic rocks of Archean–early Proterozoic age (from 2 to 3 Ga ago), which occurs as a semicircular series of prominent hills in the northern half of the area, while in the southern half the structure is partially covered by younger (Carboniferous to Permian) sediments and volcanics deposits.