Evidence of the Oblique Collision of Volgo-Sarmatia and Fennoscandia Continents During the Assembly of PaleoProterozoic Supercontinent Columbia

Trans-Baltic Palaeoproterozoic correlations towards the reconstruction of supercontinent Columbia/Nuna

Authors:

Bogdanova et al

Abstract:

A comparative study of the Palaeoproterozoic accretionary the central and southern parts Svecofennian orogen in the Baltic/Fennoscandian Shield and the platform area to the east and south of the Baltic Sea indicates that at least of these parts of the orogen are built up of several NW-SE trending, 100 to 300 km wide tectonic megadomains separated from each other and complicated by major zones of mostly dextral shearing. The generation of these zones occurred successively between 1.86 and 1.75 Ga, concomitantly with continuing crustal accretion consistently younging toward the southwest. Even considering the distorting presence of a number of microcontinents, this indicates the one-time existence and repeated episodic activity of a master subduction zone stepwise falling back toward the present south-southwest. At 1.82–1.80 Ga, the continent-continent oblique collision of megacontinent Volgo-Sarmatia with the preexisting Fennoscandia interrupted the accretionary growth of the crust in the Svecofennian orogen. In the west, the system of Svecofennian tectonic domains and shear zones is delimited by 1.70–1.55 Ga rock belts marking part of the Laurentia-Greenland-Baltica margin of Columbia. Altogether, the present U-Pb zircon datings and studies of key rocks and structures in the South Baltic region allow more detailed Trans-Baltic correlation and the creation of new integrated models of the structural and tectonic evolution of the Svecofennian orogen in particular and northern Europe in general. The new findings will be important also in the continuing study of supercontinent formation and supercontinent cycles, and the drifting of Palaeoproterozoic protocontinents during the assembly of Columbia/Nuna.