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- Title
\textbf{The age and tectonic status of the Revseggi Nappe of the southern section of the Scandinavian Caledonides}.
- Authors
Warvik, Kenneth; Ringstad, Haakon Blaker; Augland, Lars Eivind; Corfu, Fernando; Gabrielsen, Roy Helge
- Abstract
The Hardangervidda-Ryfylke Nappe Complex is one dominant element of the southernsegment of the Norwegian Caledonides. The section of Haukeli-Røldal includes the almostundisturbed Proterozoic basement, with slivers of autochtonous/parautochtonousCambrian-Ordovician sediments locally preserved. Overlying these rocks are theHolmasjø (late Neoproterozoic to Cambro-Silurian?), the Dyrskard and Kvitenut (bothMesoproterozoic) and the Revseggi (early Palaeozoic?) nappes, each separated by thrusts(Naterstad et al. 1973). The relationships between structures, metamorphism andradiometric ages show that thrusting of the Kvitenut onto the Dyrskard nappe hadoccurred already during the Sveconorwegian Orogeny (995 ± 5 Ma; Gabrielsen1976; Roffeis et al. 2013). The relationship between the Kvitenut and overlyingRevseggi nappes is, however, more enigmatic. The Revseggi Nappe consists largelyof metasedimentary rocks intruded by an (Ordovician?) bimodal sequence andmetamorphosed before its final inclusion in the Caledonian nappe stack. The interfacebetween the Kvitenut and Revseggi nappes has been interpreted both as a disturbeddepositional contact (Naterstad et al. 1973) and as a tectonic (thrust) contact (Roffeis et al.2014). The present study shows that The contact between the Kvitenut and Revseggi nappe units involves an up to 50m thick zone of imbricated mylonite gneiss with a central (2-5m thick) ultramylonite, documenting that the contact between the Kvitenut and Revseggi nappes is tectonic rather than depositional. The (top-SE) fault rocks at the contact have commonly been overprinted by large-scale extensional top-NW-extensional transport. Preliminary dating of pegmatites associated with peak metamorphism have yielded Ordovician ages, and new age determiations are in progress to clarify the age relations. Our preliminary results therefore suggest that the Revseggi Nappe was emplaced on topof the Kvitenut Nappe at an early stage of the Caledonian collision, thereafter ridingpiggy-back on a thrust unit consisting of the Dyrskard and Kvitenut nappe units that hadbecome coupled in the Sveconorwegian Orogeny. References Gabrielsen, R.H., Naterstad, J. & Råheim, A., 1979: A Rb-Sr study of a possiblePrecambrian thrust zone of the Hardangervidda- Ryfylke Nappe Complex, southernNorway.Norsk geologisk Tidsskrift, 59, 253 - 263. Naterstad,J., Andresen,A. & Jorde,K., 1973: Tectonic succession of the Caledonian nappefront in the Haukelisæter-Røldal Area, Southwest Norway. Norges Geologiske Undersøkelse,292, 1-20. Roffeis,C. & Corfu,F., 2014:Evolution and origin of the Revsegg Nappe in theSW-Norwegain Caledonides: an allochthion with Ordovician elements, in: Corfu,F.,Gasser,D. & Chew,D.M., (eds): New Perspectives on the Caledonides of Scandinavia andRelated Ares, Geological Society London, Special Publication, 390, 525-539. Roffeis, C., Corfu, F. & Gabrielsen, R.H., 2013: A Sveconorwegian terraneboundary in the Caledonian Hardanger-Ryfylke Nappe Complex: The lost link beweenTelemarkia and the Western Gneiss Region? Precambrian Research, 228, 20-35.
- Subjects
CORFU Island (Greece); PEGMATITES; GNEISS; THRUST; AGE; OROGENY; THRUST faults (Geology); ORDOVICIAN Period
- Publication
Geophysical Research Abstracts, 2019, Vol 21, p1
- ISSN
1029-7006
- Publication type
Article