Baltica

Baltica is a paleocontinent that formed in the Paleoproterozoic and now constitutes northwestern Eurasia, or Europe north of the Trans-European Suture Zone and west of the Ural Mountains.The thick core of Baltica, the East European Craton, is more than three billion years old and formed part of the Rodinia supercontinent at c. 1 Ga.AfricaAntarcticaAsiaAustraliaEuropeNorth AmericaSouth AmericaAfro-EurasiaAmericaEurasiaOceaniaSubcontinents Baltica is a paleocontinent that formed in the Paleoproterozoic and now constitutes northwestern Eurasia, or Europe north of the Trans-European Suture Zone and west of the Ural Mountains.The thick core of Baltica, the East European Craton, is more than three billion years old and formed part of the Rodinia supercontinent at c. 1 Ga. Baltica formed at c. 2.0–1.7 Ga by the collision of three Archaean-Proterozoic continental blocks: Fennoscandia (including the exposed Baltic Shield), Sarmatia (Ukrainian Shield and Voronezh Massif), and Volgo-Uralia (covered by younger deposits). Sarmatia and Volgo-Uralia formed a proto-craton (sometimes called 'Proto-Baltica') at c. 2.0 Ga which collided with Fennoscandia c. 1.8–1.7 Ga. The sutures between these three blocks were reactivated during the Mesoproterozoic and Neoproterozoic. 750–600 million years ago, Baltica and Laurentia rotated clockwise together and drifted away from the Equator towards the South Pole where they were affected by the Cryogenian Varanger glaciations. Initial rifting between the two continents is marked by the c. 650 Ma Egersund dike swarm in southern Norway and from 600 Ma they began to rotate up to 180° relative to each other, thus opening the Iapetus Ocean between them. Laurentia quickly moved northward but Baltica remained an isolated continent in the Southern Hemisphere closer to Gondwana on which endemic trilobites evolved in the Early Ordovician. During the Ordovician, Baltica moved northward approaching Laurentia again allowing trilobites and brachiopods to cross the Iapetus Ocean. In the Silurian, c. 425 Ma, the final collision between Scotland-Greenland and Norway resulted in the Scandian Orogeny. Baltica is a very old continent and its core is a very well-preserved and thick craton. Its current margins, however, are the sutures that are the result of mergers with other, much younger continental blocks. These often deformed sutures do not represent the original, Precambrian–early Palaeozoic extent of Baltica; for example, the curved margin north of the Urals running parallel to Novaya Zemlya was probably deformed during the eruption of the End-Permian Siberian Traps. Baltica's western margin is the Caledonide orogen which stretches northward from the Scandinavian Mountains across Barents Sea to Svalbard. Its eastern margin is the Timanide orogen which stretches north to the Novaya Zemlya archipelago.The extent of the Proterozoic continent are defined by the Iapetus Suture to the west; the Trollfjorden-Komagelva Fault Zone in the north; the Variscan-Hercynian suture to the south; the Tornquist Zone to the southwest; and the Ural Mountains to the east. At c. 555 Ma during the Timanian Orogeny the northern margin became an active margin and Baltica expanded northward with the accretion of a series of continental blocks: the Timan-Pechora Basin, the northern-most Ural Mountains, and the Novaya Zemlya islands. This expansion coincided with the Varanger glaciations, also known as Snowball Earth. Terranes of the North American Cordillera, including Alaska-Chukotka, Alexander, Northern Sierra, and Eastern Klamath, share a rift history with Baltica and most likely were part of Baltica from the Caledonian orogeny to the formation of the Ural Mountains.These terranes can be linked to either northeastern Laurentia, Baltica, or Siberia because of a similar sequence of fossils; detrital zircon from 2–1 Ga-old sources and evidence of Grenvillian magmatism; and magmatism and island arcs from the Late Neoproterozoic and Ordovician-Silurian. From at least 1.8 Ga to at least 0.8 Ga the southwestern margin of Baltica was connected to Amazonia while the southeast margin was connected to the West African Craton.Baltica, Amazonia, and West Africa rotated 75° clockwise relative to Laurentia until Baltica and Amazonia collided with Laurentia in the 1.1–0.9 Ga Grenville-Sveconorwegian-Sunsás orogenies to form the supercontinent Rodinia. When the break-up of Rodinia was complete c. 0.6 Ga Baltica became an isolated continent — a 200 million year period when Baltica was truly a separate continent.Laurentia and Baltica formed a single continent until 1.265 Ga which broke up some time before 0.99 Ga. After the subsequent closure of the Mirovoi Ocean Laurentia, Baltica and Amazonia remained merged until the opening of the Iapetus Ocean in the Neoproterozoic.