New Developments in the Appalachian-Caledonian-Variscan Orogen

New analytical and field techniques, as well as increased international communication and collaboration, have resulted in significant new geological discoveries within the Appalachian-Caledonian-Variscan orogen. Cross-Atlantic correlations are more tightly constrained and the database that helps us understand the origins of Gondwanan terranes continues to grow. Special Paper 554 provides a comprehensive overview of our current understanding of the evolution of this orogen. It takes the reader along a clockwise path around the North Atlantic Ocean from the U.S. and Canadian Appalachians, to the Caledonides of Spitsbergen, Scandinavia, Scotland and Ireland, and thence south to the Variscides of Morocco.
Revised tectono-stratigraphic scheme for the Scandinavian Caledonides and its implications for our understanding of the Scandian orogeny
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Published:May 19, 2022
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CiteCitation
Johannes Jakob, Torgeir B. Andersen, Geoffroy Mohn, Hans Jørgen Kjøll, Olivier Beyssac, 2022. "Revised tectono-stratigraphic scheme for the Scandinavian Caledonides and its implications for our understanding of the Scandian orogeny", New Developments in the Appalachian-Caledonian-Variscan Orogen, Yvette D. Kuiper, J. Brendan Murphy, R. Damian Nance, Robin A. Strachan, Margaret D. Thompson
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ABSTRACT
The Scandinavian Caledonides formed during the continental collision between Baltica and Laurentia. During the collision, a complex nappe stack was thrust over the Baltican continental margin. The orogen can be subdivided into segments based on architectural differences within the Scandian nappes. The southern and central segments of the orogen link up in the Gudbrandsdalen area in south-central Norway. Alpine-type metaperidotite-bearing metasedimentary complexes occur in the southern and central segments and can be traced continuously along the strike of the orogen from one into the other segment. Traditionally, these units have been assigned to different tectono-stratigraphic levels, one below the Middle Allochthon and one above the Middle Allochthon. Here, we trace the Alpine-type metaperidotite-bearing units from Bergen to Esandsjøen and show that these units exhibit a common geologic and metamorphic history, consistent with the metaperidotite-bearing units representing a single tectonic unit. We suggest that the metaperidotite-bearing units can be used as a “marker level” to revise the tectono-stratigraphy of the Gudbrandsdalen and adjacent areas. The tectono-stratigraphic revisions imply that the Scandian nappe stack consists of seven tectono-stratigraphic levels that can be traced throughout the southern and central segments of the Scandinavian Caledonides. Moreover, the revision of the tectono-stratigraphy and new U-Pb geochronology data also suggest a revision of the timing of the succession of tectonic events leading up to the Scandian continental collision. The available evidence indicates that Baltica-derived tectonic units collided with the Iapetan/Laurentian subduction complexes as early as ca. 450 Ma. The initial collision was followed by in-sequence nappe formation of Baltican-derived units, which occurred contemporaneously with the opening of a marginal basin in the upper plate. After the arrival of thick, buoyant, unthinned Baltican crust at the trench, the main zone of convergence stepped outboard, the marginal basins closed, and those basins were thrust out-of-sequence over the previously assembled nappe stack.
- absolute age
- allochthons
- Baltica
- Caledonides
- Cambrian
- continental crust
- correlation
- crust
- Cryogenian
- dunite
- eclogite
- Ediacaran
- Europe
- faults
- felsic composition
- gabbros
- granites
- graphitization
- hydrothermal alteration
- igneous rocks
- Laurentia
- lithostratigraphy
- mafic composition
- marker beds
- metaigneous rocks
- metamorphic rocks
- metamorphism
- metaperidotite
- metasedimentary rocks
- metasomatism
- nappes
- Neoproterozoic
- nesosilicates
- oceanic crust
- ophiolite
- Ordovician
- organic compounds
- orthosilicates
- Paleozoic
- peridotites
- plate collision
- plate tectonics
- plutonic rocks
- Precambrian
- Proterozoic
- protoliths
- Scandian Orogeny
- Scandinavia
- serpentine
- serpentine group
- serpentinization
- shear zones
- sheet silicates
- silicates
- Silurian
- subduction
- thermodynamic properties
- Tonian
- U/Pb
- ultramafics
- upper Precambrian
- Western Europe
- whole rock
- zircon
- zircon group
- Samnanger Complex
- Gudbrandsdalen Norway