Baltica, Amazonia and the SAMBA connection—1000 million years of neighbourhood during the Proterozoic?

Possible large-scale geological correlation between Baltica (East European Craton) and Amazonia (central South America) is discussed using compilations of recent data and regional geological models. A fit with northwest Amazonia attached to southwest Baltica – the SAMBA (South America–Baltica) connection – produces a closely matching pattern of westward younging Proterozoic growth zones and is suggested to have existed from at least 1.8 Ga to at least 0.8 Ga. West Africa was probably attached to northeast Amazonia and southeast Baltica during the same time period. As in most plate tectonic reconstructions, northwest Baltica was attached to eastern Laurentia (Greenland) from 1.9 Ga to at least 1.3 Ga, and western Amazonia thus formed a continuation of the southeast Laurentia–western Baltica active margin, being characterized by intermittent crustal growth and orogenic deformation during the late Palaeoproterozoic and Mesoproterozoic, as well as periods with more inboard intraplate magmatism. In order to reach the “standard” Rodinia configuration, Baltica must have separated from Laurentia and, together with Amazonia and West Africa, rotated c. 75° clockwise relative to Laurentia. During the 1.1–0.9 Ga Grenvillian – Sveconorwegian – Sunsas orogeny, the western margin of Baltica and Amazonia collided with the southeast margin of Laurentia, as part of the formation of the Neoproterozoic supercontinent Rodinia. Final break-up of Rodinia occurred around 0.6 Ga, although separation of Amazonia and West Africa from Baltica may have occurred earlier. With ocean opening along the southwest (Tornquist) and northwest (Iapetus) margins of Baltica, and the formation of the Timanian orogen along the leading northeastern edge at 0.6–0.55 Ga, Baltica moved to the (present-day) northeast, into a 200 million year period of solitude, the only period during its history when Baltica existed as a continent of its own, before reuniting with Laurentia during the Caledonian orogeny and then merging with the rest of Eurasia.