Definition of Archean Cratonic Basins

A third style of rock association also typifies the Archean but

is less common than the previous two associations. The cratonic

basin association is characterized by little-deformed and

metamorphosed sequences of clastic and carbonate sedimentary

rocks, with a few intercalated volcanic horizons. This category

of Archean sequence is most well developed on South

Africa’s Kaapvaal craton and includes the Pongola, Witwatersrand,

Ventersdorp, and Transvaal Supergroups. These groups

include sequences of quartzites, sandstones, arkoses, carbonates,

and volcanic rocks, deposited in shallow marine to lacustrine

basins. They are interpreted to represent rift, foreland

basin, and shallow marine cratonic epeirogenic sea type

deposits, fortuitously preserved although only slightly metamorphosed

and deformed. Several shallow-water carbonate

shelf associations are also preserved, including the 3.0 Ga

Steep Rock platform in Canada’s Superior Province, and possibly

also the 2.5 Ga Hamersley Group in western Australia.

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