Scandinavian Caledonides

The Scandinavian Caledonides are the vestiges of an ancient, today deeply eroded orogenic belt formed during the Silurian–Devonian continental collision of Baltica and Laurentia, which is referred to as the Scandian phase of the Caledonian orogeny.

[12] The area east of the Scandinavian Caledonides, including parts of Finland, developed into a foreland basin where old rocks and surfaces were covered by sediments.

The Caledonian Wilson cycle commenced with the continental break-up of Rodinia[17] and the opening of the Iapetus ocean about 616–583 Ma (mega-annum) ago.

[1][22][23] Subduction of Iapetus crust continued until about 430 Ma ago until the final continental collision of Laurentia with Baltica, i.e. the Scandian phase of the Caledonian orogeny.

The time of the continental collision is estimated by the cessation of subduction-related magmatism and a common apparent polar wander path (APWP) for Laurentia and Baltica.

The time of the maximal burial of the Baltican margin is estimated at 410 Ma ago by radiometric age dating of the ultra-high pressure (UHP) metamorphism in the Western Gneiss Region (WGR).

Location of the different branches of the Caledonian/ Acadian belts at the end of the Caledonian orogeny (Early Devonian ). [ 1 ] [ 2 ] [ 3 ] [ 4 ] [ 5 ] Present day coastlines are indicated in gray for reference. Note, that the North-German–Polish Caledonides were not formed during the Scandian orogeny but during the "soft docking" of East Avalonia to Baltica at about 443 Ma. [ 1 ] [ 6 ] [ 7 ] The Acadian orogeny resulted from the prolonged collision of the "peri- Gondwanan terranes " with the Laurentian autochthon. [ 1 ] Later in geological history , the North Atlantic Ocean opened [ 8 ] [ 9 ] [ 10 ] and the different parts of the orogenic belt moved apart. See also Iapetus Suture and Trans-European Suture Zone .
A conceptual NW-SE oriented cross section of the Scandinavian Caledonides near Torneträsk in northernmost Sweden. Each nappe is shown with a different colour. Arrows show the relative movement of each nappe. The décollement plane is shown as black dented line. Note the general movement towards the southeast.