Accretion, rifting, rotation and collision in the North Atlantic supercontinent, 1700-950 Ma

Abstract

Abstract Events in the North Atlantic region, from c. 1700 to 950 Ma, are unified in a model compatible with palaeomagnetic results and Neoproterozoic supercontinent reconstructions. Following Labradorian-Gothian accretion, largely between 1700 and 1550 Ma, post-collisional effects continued until c. 1500 Ma. Continental extension from c. 1500 Ma onwards, related to ocean opening, developed granite-rhyolite provinces: the Central Metasedimentary Belt (Grenville Province) started to form at c. 1425 Ma, with arcs outboard at c. 1350–1300 Ma. Baltica started to separate from Laurentia and rotate at c. 1240 Ma, causing crustal delamination of its leading edge, in South Norway. Here, subduction-related gabbroids intruded at c. 1230–1225 Ma, as rotation proceeded. The Elzevirian Orogeny occurred at c. 1190 Ma in the Southwest Grenville Province, marking the start of convergence of Baltica, in which backarc extension was accompanied by granites and bimodal volcanics. Collision at c. 1080 Ma caused the Ottawan Orogeny which thrust accreted terranes northwestwards and closed the Mid-Continental Rift. In southern Baltica, complex deformation occurred. Post-collisional convergence and sinistral slip of Baltica against Laurentia (possibly related to convergence of Amazonia) caused thrusting, sinistral strike-slip faulting, folding and granitic intrusion until c. 950 Ma. Post-tectonic granites intruded until c. 900 Ma.