A timeline of the earth's history indicating when the Vredefort crater was formed in relation to some of the other important South African geological events. W indicates when the Witwatersrand Supergroup was laid down, C the Cape Supergroup, and K the Karoo Supergroup. The graph also indicates the period during which banded ironstone formations were formed on earth, indicative of an oxygen-free atmosphere. -- Vredefort crater - Wikipedia
VREDEFORT CRATER, South Africa: is the largest verified impact crater on Earth. Although the crater itself has long since eroded away, the remaining geological structures at its centre are known as the Vredefort Dome or Vredefort impact structure. The crater's age is estimated to be 2.023 billion years.