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Cratons of South America and Africa during the Triassic Period when the two continents were joined as part of the Pangea supercontinent. A craton (/ ˈ k r eɪ t ɒ n / KRAYT-on, / ˈ k r æ t ɒ n / KRAT-on, or / ˈ k r eɪ t ən / KRAY-tən; [1] [2] [3] from Ancient Greek: κράτος kratos "strength") is an old and stable part of the continental lithosphere, which consists of Earth's two ...
Nevertheless, the oldest cratons on Earth include the Kaapvaal Craton, the Western Gneiss terrane of the Yilgarn Craton (~2.9 – >3.2 Ga), the Pilbara Craton (~3.4 Ga), and portions of the Canadian Shield (~2.4 – >3.6 Ga). Parts of Dharwar Craton in India are greater than 3.0 Ga. The oldest dated rocks of the Baltic Shield are 3.5 Ga old. [10]
A craton is an ancient part of the Earth's continental crust which has been more or less stable since Precambrian times. Cratons whose ancient rocks are widely exposed at the surface, often with relatively subdued relief, are known as shields.
The degree of certainty to which the identified landmasses can be regarded as independent entities reduces as geologists look further back in time. The list includes cratons, supercratons, microcontinents, continents and supercontinents. For the Archean to Paleoproterozoic cores of most of the continents see also list of shields and cratons.
The Kaapvaal Craton covers an area of approximately 1,200,000 km 2 (460,000 sq mi) and is joined to the Zimbabwe Craton to the north by the Limpopo Belt.To the south and west, the Kaapvaal Craton is flanked by Proterozoic orogens, and to the east by the Lebombo monocline that contains Jurassic igneous rocks associated with the break-up of Gondwana.
c. 3,800 Ma – Oldest banded iron formations found. [9] First complete continental masses or cratons, formed of granite blocks, appear on Earth. Occurrence of initial felsic igneous activity on eastern edge of Antarctic craton as first great continental mass begins to coalesce.
Cheney 1996, nevertheless, found a three-fold stratigraphic similarity and proposed that the two cratons once formed a continent which he named Vaalbara. This model is supported by the palaeomagnetic data of Zegers, de Wit & White 1998. [4] Reconstructions of the palaeolatitudes of the two cratons at 2.78–2.77 Ga are ambiguous however.
The craton is a composite of several different terranes of Archaean metasediments. The Dodoman is the oldest, and others include the Nyanzian and Kavirondian. Some of the greenstone belts are more than 3 billion years old. They were intruded by granites and migmatized in different events that date back to 2.9, 2.7, 2.4 and 1.85 billion years ...