A comparison of two orogenic margins: Central Scandinavian Caledonides and western Outer Carpathians

This study compares two marginal fold-and-thrust belts in order to assess their orogenic evolution and related processes. The Scandinavian Caledonide margin developed during Silurian-Early Devonian times. The orogenic wedge overlies a wide passive margin and incorporated crystalline basement rocks. Foreland basin development is documented for the first c. 15 Ma but lasted probably longer. Basin width exceeded 300 km, molasse sediments are less than 2 km thick. Polyphase structural and metamorphic evolution, basement involvement, and post-collisional convergence characterise the Scandinavian Caledonides as orogen of Alpine-Himalayan type. Convergence may have been oblique. Late-orogenic loads prevented the evolution of a major high mountain-large foredeep system. Subsequent transpressional basin formation is concentrated in the internal parts of the orogen. The Carpathian foreland basin formed during the last 17 Ma and is up to 100 km wide. Molasse sediments are 3 km (W) to 10 km (E) thick. The orogenic wedge overlies a narrow pre-orogenic passive margin and there is no basement involvement. However, inversion of rifts led to thickening of the underlying crust. Regional extension, little metamorphism, and little deformed basement show the Outer Carpathians as an orogen of Apenninic type. Oblique convergence led to a migration of orogenic deformation along the strike of the belt.