Early partitioning of Quebec: Microcontinent formation in the Paleoproterozoic

The distribution of allochthonous versus parautochthonous carbonate platfor ms, combined with the timing of initial continental-rift magmatism versus t he timing of subsequent rifting of the continental margin, provides tectono stratigraphic evidence for the formation and isolation of the oldest docume nted microcontinent, perhaps as a consequence of the impingement of a mantl e plume onto a cratonic margin during the Paleoproterozoic, Initial rifting of the Archean nucleus of North America in eastern Canada is constrained t o have been diachronous between 2.17 and 2.03 Ga, Renewed rifting of a segm ent of the continental margin, 292 to 120 m.y. later, was accompanied by th e emplacement of ultramafic layered sills, the accumulation of komatiitic a nd alkalic basalts, the deposition of banded iron formations and the isolat ion of a microcontinent and its 1.93 Ga continental shelf succession (subse quently accreted to the telescoped continental margin during collisional or ogenesis).