Precambrian continent

Precambrian continent
In his reconstruction of the supercontinent cycle, Rogers proposed that the continent Ur formed at about 3 Ga and formed East Gondwana in the Middle Proterozoic by accretion to East Antarctica; Arctica formed around 2.5–2 Ga by the amalgamation of the Canadian and Siberian shields plus Greenland; and Atlantica formed around 2 Ga by the amalgamation of the West African Craton and eastern South America. Arctica then grew around 1.5 Ga by accretion of East Antarctica and Baltica to form the supercontinent Nena. Around 1 Ga Nena, Ur, and Atlantica collided to form the supercontinent Rodinia.[8]

Rogers & Santosh 2003 argued that most cratons that were around at 2.5 Ga most likely formed in a single region simply because they were located in a single region in Pangaea, which is the reason Rogers argued for the existence of Arctica. The core of Arctica was the Canadian Shield, which Williams et al. 1991 named Kenorland. They argued that this continent formed around 2.5 Ga then rifted before reassembling along the 1.8 Ga Trans-Hudson and Taltson-Thelon orogenies. These two orogenies are derived from continental crust (not oceanic crust) and were probably intracontinental, leaving Kenorland intact from 2.5 Ga to present. Correlations between orogenies in Canada and Siberia remain more controversial.[9]

Laurentia and Baltica were connected during the Late Palaeoproterzoic (1.7–1.74 Ga) and Siberia later joined them. Paleomagnetic reconstructions indicate that they formed a single supercontinent during the Mesoproterozoic (1.5–1.45 Ga) but paleomagnetic data and geological evidences also suggest a considerable spatial gap between Siberia and Laurentia and Arctica is thought to be the missing link.[10]