Search results
Results from the WOW.Com Content Network
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.
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]
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 ...
The Kaapvaal craton is marked by dramatic events such as the intrusion of the Bushveld Complex (2.045 Ga) and the Vredefort impact event (2.025 Ga), and no traces of these events have been found in the Pilbara craton, clearly indicating that the two cratons were separated before 2.05 Ga. [10] Furthermore, geochronological and palaeomagnetic ...
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 Limpopo belt formed contemporaneously with the Zimbabwe and Kaapvaal cratons, but remained geologically active until much later. It was only in the late Archean, ca. 2.8-2.5 Ga., that the two cratons were stabilized together and that high-grade metamorphism ceased in the Limpopo Belt. North of the Zimbabwe Craton is the Zambezi Belt. [2]
The Slave Craton includes the 4.03 Ga-old Acasta Gneiss which is one of the oldest dated rocks on Earth. [1] [2] Covering about 300,000 km 2 (120,000 sq mi), it is a relatively small but well-exposed craton dominated by ~2.73–2.63 Ga (billion years-old) greenstones and turbidite sequences and ~2.72–2.58 Ga plutonic rocks, with large parts ...
The Montana metasedimentary province and Beartooth–Bighorn magmatic zone were established as cratons by about 3.0–2.8 Ga. Crustal growth occurred through a combination of continental-arc magmatism resulting from oceanic crust subducted beneath continental crust on an adjacent plate, creating an arc-shaped mountain belt, together with ...