Baltica

Baltica, in German also Baltika was a continent in the Earth's history, which was ( approximately 570-550 mya ) originated in the uppermost Neoproterozoic, in Llandovery, the older section of the Silurian (ca. 440-430 mya ), with the geological continent of Laurentia collided and thus became an essential part of the earth's major continent Laurussia. It consisted of areas in the older geological literature as Fennosarmatia (composed of Fenno for Finland and Sarmatia ) or Fennoscandia, were referred to in the older German usage as Ureuropa.

Naming

For this geological continent a group of authors suggested to Alfred M. Ziegler, before 1977 the name Baltica. He quickly found in literature and supplanted the older terms Fennosarmatia, Fennoscandia and Ureuropa, but they are also basically not synonyms, as they are structural or regional geological terms. However, for example, found in the case Laurentias also a senior structural geological term for the geological continent use.

Geographical expansion

The boundaries of the geological continent Baltica today consist Geosuturen or large disturbances, which in part caused only by much later tectonic activity; that is, the limits Balticas how they are being represented today been greatly changed the time of the existence of the geological Baltica with respect to the original boundaries. Therefore, the description of the geological Baltica based on today's geography can only be very rough. Baltica existed at the time of its maximum size the greater part of Northern Europe and Eastern Europe to the Urals. In Central Europe, the western border is roughly formed by the northwest -southeast - running Trans-European Suture Zone. In the Caledonian folded western Scandinavia, the border is within the Caledonian ceiling stack. In the south of the border is even less clear, as it has been strongly deformed here several times by later orogenies. It runs from the Trans-European suture zone starting about of Moldova, north of the Black Sea to the Urals. In the Northeast were among the Timanrücken and today subsequent to the north continental shelf with the Spitsbergen archipelago and the Franz Josef Land to do so. These areas were welded to the continent during the stand-alone story Balticas. In total, the area that once formed the geological continent of Baltica, approximately 8 million km2.

Geological structure and early history

Baltica had and consists of three old cores: Fennoscandia, Sarmatia and Volgo - URALIA. Fennoscandia, in turn, can be divided into two parts: an archaic core in the northeast and a southwest zone with Proterozoic rocks that are mya old between 2500-1700.

The gneisses belonging to the archaic core Kola Peninsula are with 2700-3500 ma the oldest rocks in Europe. You may have been made from the first archaic Ur supercontinent. Few rocks of the earth are even older ( 4300-3800 mya ), the Acasta gneisses and Nuvvuagittuq greenstone belt of Canada or the Isua gneisses in Greenland.

Fennoscandia was mya to 1900 merged with the recently united Volgo - URALIA and Sarmatia. The area was mya order from 1100 to 1000 a part of the supercontinent Rodinia. Baltica is the first tangible than before about 800 million years ago broke up the supercontinent Rodinia. Baltica probably depended at that time with Laurentia together and formed with him a large continent, a forerunner of the later Laurussia. However, Baltica was compared to the later position occupied in Laurussia rotated 120 ° clockwise.

Baltica as a separate continent of geological

Probably around 580 mya, the Iapetus Ocean opened between the combined Laurentia / Baltica and Gondwana. To 570-550 mya Spreading the migrated further north between Laurentia and Baltica; as the northern part of the Iapetus Ocean and Baltica was created had become a separate continent, lying between 30 ° and 60 ° south latitude at that time. Around 550 mya several small terranes were welded to today's northeastern edge Balticas and formed the Timaniden. The Timanrücken is located north of the Urals and the rest of this orogeny. These accreted at this time areas and the continental shelf north of Timangebirges belonged to Spitsbergen. This part Balticas formed at this time, the southeastern tip Balticas, due to the subsequent 120 ° rotation counterclockwise. Neoproterozoic tillites, which were found in this region are in good agreement with a position in high southern latitudes. Gondwana and Baltica were separated by a relatively narrow ocean area, which was called by the geologists Ebbe Hartz and Trond Torsvik 2002 Ran Ocean. Between Baltica and Sibiria, which lay east of Baltica, the Aegir Ocean had opened. The northern edge of Gondwana, which was then formed by Avalonia and Armorica or the Hun - Super Terran has been detected 650-550 ma of the Cadomian orogeny.

Even in the highest Ediacaran began a transgression on the edges Balticas. The relief seems to have been relatively flat. The Faziesräume in the Cambrian are relatively uniform over large distances and a large part of the continent was covered by shallow seas. The widths are relatively small and indicate low sediment delivery and thus back again to a low relief in the hinterland. In the Upper Cambrian of the present north western edge of Baltica from the Finnmark orogeny was detected (about 505-500 mya ), which is probably related to the subduction of the ocean Aegir - in connection. In the Cambrian, the 120 ° rotation of Baltica began counterclockwise. In Unterordovizium to Avalonia broke from the northern edge of Gondwana and drifted north on Baltica, while the Rheische Ocean opened. In the upper Ordovician Avalonia collided with Baltica now rotated to his current position. During the Silurian Baltica / Avalonia collided with Laurentia eventually became the new Grand Continent Laurussia. In Europe, this collision caused the Caledonian orogeny and the Taconic orogeny in North America. Thus ended the story Balticas as an independent continent of geological history. In the Carboniferous of the western part of Gondwana collided with Laurussia, in the Lower Permian Sibiria was welded to Laurussia and the actual Pangaea was formed.