Ag. Milnes et Ha. Koyi, Ductile rebound of an orogenic root: case study and numerical model of gravity tectonics in the Western Gneiss Complex, Caledonides, southern Norway, TERRA NOVA, 12(1), 2000, pp. 1-7
The main Caledonian deformation in the Western Gneiss Complex (southern Nor
way) has been interpreted as resulting from the gravity-driven ductile rebo
und of the orogenic root. Detailed field data from the Sognefjord profile,
a 60-km long, continuously exposed shore section through the complex, are c
ompared with the results of a numerical scale model of root rebound dimensi
oned according to reconstructions of the overall tectonic evolution. The st
rain pattern in the model can be closely tied to the previously recognized
structural regimes, from east to west: R1 - little deformed Precambrian bas
ement (stiff orogenic lid, basal part of upper crust); R2 - heterogeneously
sheared basement ('simple shear' domain at upper crust/lower crust boundar
y); R3 - completely overprinted basement with eclogitic remnants ('pure she
ar' regime in the lower crust of the rebounded root). Subsequent to root re
bound the profile remained practically unaffected by later tectonic events,
except for tilting/uplift/erosion. providing a unique example of deep-seat
ed gravity tectonics.