Correlations between the Grenville Province and Sveconorwegian Orogenic Belt — Implications for Proterozoic Evolution of the Southern Margins of the Canadian and Baltic Shields

Abstract

Adopting the hypothesis that the Grenville and Sveconorwegian fronts were part of the same tectonic margin during Lower-Middle Proterozoic times, and that the Baltic Shield rotated clockwise relative to the Canadian Shield prior to, and (or) during the Grenville Orogeny, the following model is proposed. The Archean cratons extending from Wyoming, U.S.A. to central Europe formed a linear protocontinent, on the peripheries of which continental margin sediments accumulated. Subsequently the southern Canadian and Baltic Shields bee ame the site of a long—lived Lower to Middle Proterozoic continental margin convergent plate boundary. Rotation of the Baltic Shield relative to the Canadian Shield initiated an intermittent Middle Proterozoic rifting regime and eventually caused progressive collision along the Canadian-Baltic Shield mutual southern boundaries, resulting in interior thrusting and regional structural trends oblique to orogen margins. A complimentary tensional regime farther north eventually triggered Late Proterozoic rifting that presaged the early Phanerozoic Iapetus Ocean.