Baltic shield

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Map of the geological provinces of Fennoskandia
  • Archean of the Kola Peninsula and Karelia
  • Proterozoic of the Kola Peninsula and Karelia
  • Svekofenniden
  • Trans-Scandinavian magmatite belt
  • Danopolonids
  • Svekonorwegids
  • Scandinavian Caledonids
  • Non-metamorphic Neoproterozoic of the Varanger Peninsula
  • Unfolded Phanerozoic
  • The Baltic Shield or Fennoscandian Shield is called the larger of the two regions of Europe in which the geologically very old core of the continent is revealed today . It covers most of the region known as Fennoscandinavia and dips to the southeast under the Eastern European table . It is made of crystalline rocks ( gneisses , granitoids , crystalline schists built) whose metamorphosis - and crystallization age the formation of primordial Europe ( Baltica ) from individual small continents (terranes) during the Precambrian documented. The second and significantly smaller European shield region is the Podolian shield .

    Emergence

    The earlier mountains, unfolded at least a billion years ago, have been eroded to form relatively flat rump mountains since their formation .

    The Baltic Shield covers most of the Scandinavian Peninsula (excluding the Scandinavian Mountains ), Finland , Eastern Karelia and the Kola Peninsula . The mainland core was firmly welded through multiple Precambrian folds and metamorphoses .

    The Baltic Shield was always moderately uplifted throughout at least the entire Phanerozoic and therefore a high area. However, the load of the kilometer-thick ice sheet that repeatedly covered the shield over the past two million years ( Pleistocene ) caused the earth's crust to sink slightly into the earth's mantle . Since the ice sheet disappeared again around 10,000 years ago, the shield has been rising more and more due to the reduced pressure load ( postglacial land elevation ), which is clearly visible on the coasts of the Baltic Sea . This effect allows geophysical conclusions to be drawn about the elasticity of the upper mantle .

    Tectonic division

    Due to the predominantly highly metamorphic rocks of the Baltic Shield, deciphering its geological history was difficult for a long time. It was only through the use of radiometric dating methods that it was possible to reconstruct the actual age relationships within the Baltic Shield. This established that the Baltic Shield is composed of several rock provinces of different ages, which represent different orogeny cycles .

    The determined radiometric age data made it possible to subdivide the Baltic Shield from northeast to southwest into the following areas:

    • Saamids - Orogenetic imprint predominantly between 2.6 and 2.8 Ga (especially Kola Peninsula, Karelia and eastern central Finland)
    • Belomorids - minted about 2 Ga (location within the Saamids in the area of ​​the White Sea)
    • Svekokareliden - minted around 1.8 Ga, further subdivision into Kareliden in the north and Svekofenniden in the south (SW-, NW-Finland and NE-Sweden)
    • Svekonorwegiden - minted around 1 Ga (SW Sweden and southern Norway)

    See also

    literature

    • Peter Faupl: Historical Geology. An introduction. (= UTB . 2149). 2nd, improved edition. facultas wuv, Vienna 2003, ISBN 3-8252-2149-0 .
    • Reinhard Schönenberg, Joachim Neugebauer: Introduction to the geology of Europe. 7th, revised edition. Rombach GmbH printing and publishing house, Freiburg im Breisgau 1997, ISBN 3-7930-9147-3 .

    Web links