Deformable plate reconstructions of Atlantic Canada and its conjugates back to the Paleozoic

Atlantic Canada and its conjugate margins, the Irish, Iberian, and Moroccan margins, were subject to rifting and eventual breakup during the Mesozoic, following prior Appalachian Orogenesis from the early to mid-Paleozoic. The complexities of that older orogenesis, involving accretion and collision of Laurentian and peri-Gondwanan terranes during the closing of the Iapetus Ocean, contributed to the heterogeneous pre-rift template of the modern southern North Atlantic Ocean and the timing and extent of subsequent rift-related deformation.

In this work, we present newly-derived offshore and onshore present-day crustal thickness estimates of Atlantic Canada that are calculated using constrained 3-D gravity inversion and later reconstructed back to the onset of rifting and beyond, using GPlates and pyGPlates. In addition, deformable plate reconstructions are also used to reconstruct present-day magnetic anomalies, both onshore and offshore, back through time to track Appalachian orogenic trends beyond what can be deduced from geological field mapping alone. With the pre-rift template of the southern North Atlantic Ocean restored, we then attempt to extend these reconstructions further back in time to the Paleozoic to investigate strain localization within and between Appalachian terranes. Our results clearly reveal the fundamental influence of orogenic inheritance on subsequent rift events and the present-day variations in the crustal architecture that are observed along rifted margins. This study also provides the first quantitative assessment of Atlantic Canada’s crustal evolution from a compressive regime, to an extensional regime, to passive margin development.