Remains of an orogenic belt formed during the Silurian–Devonian period
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-Gondwananterranes" 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.
The Scandinavian Caledonides are the vestiges of an ancient, today deeply eroded
Scandian phase of the Caledonian orogeny.[11] The size of the Scandinavian Caledonides at the time of their formation can be compared with the size of the Himalayas.[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.[13] Today, the Scandinavian Caledonides underlay most of the western and northern Scandinavian Peninsula,[14][15] whereas other parts of the Caledonides can be traced into West and Central Europe as well as parts of Greenland[16]
and eastern North America.
Plate-tectonic history
The Caledonian
Early Ordovician[21][1] before it began to close by subduction of Iapetus crust along the Gondawanan and Laurentian margins starting between 500 and 488 Ma ago.[1][22][23] Subduction of Iapteus 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.[24][7]
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.
The Caledonian orogeny put in place most of the
provinces. The Caledonian rocks form large nappes (Swedish: skollor) that have been thrust over the older rocks. Much of the Caledonian rocks have been eroded since they were put in place meaning that they were once thicker and more contiguous. It is also implied from the erosion that the nappes of Caledonian rock originally reached further east than they do today. The erosion has left remaining massifs of Caledonian rocks and windows of Precambrian-aged rock.[27]
While there are some disagreements, geologists generally recognize four
sedimentary rocks. Pieces of Precambrian shield rocks are in some places also incorporated into the Lower nappes.[27]
Present-day topography of Scandinavia
Despite occurring in roughly the same area, the ancient Scandinavian Caledonian Mountains and the modern Scandinavian Mountains are not synonymous. The overlap between the Scandinavian Caledonides and the Scandinavian Mountains has led to various suggestions that the modern Scandinavian Mountains are a remnant of the Caledonide mountains.
orogenic collapse for a long period starting in the Devonian.[14][31][26] Another problem with this model is that it does not explain why other former mountains dating back to the Caledonian orogeny are eroded and buried in sediments and not uplifted by their "roots".[14] Others claim that molten magma exists below the Caledonides of Norway, causing the uplift.[32]
^Mosar, Jon; Eide, Elizabeth A.; Osmundsen, Per Terje; Sommaruga, Anna; Torsvik, Trond H. (2002). "Greenland-Norway separation: A geodynamic model for the North Atlantic". Norwegian Journal of Geology. 82: 281–298.
^Stephens, M. B.; Gee, David G. (1985). "A tectonic model for the evolution of the eugeoclinal terranes in the central Scandinavian Caledonides". The Caledonide Orogen—Scandinavia and Related Areas: 954–978.
