Tracing Polyphase Fault Reactivation and Lithospheric Evolution Through Wilson Cycles: Thermochronological Insights From the Newfoundland Appalachians

Fault reactivation and exhumation‐related cooling are predicted by the Wilson cycle and models for the assembly and dispersal of continents. New thermochronology data and thermal history models of basement rocks in the Newfoundland Appalachians in Atlantic Canada were conducted to test these models and track connections between structural inheritance, rock exhumation, and amalgamation and breakup of supercontinent Pangea in eastern North America. The stages at the end of the last Wilson cycle, which in the Newfoundland Appalachians culminated with subduction‐related ocean closure and Paleozoic continental assembly, are exemplified by accelerated cooling (>1°C Myr −1 ) and ∼5–12 km of rock exhumation along segments of the inherited Avalonia‐Ganderia suture zone. Our results confirm that continental extension initiated at ∼255 Ma. This start of a new Wilson cycle involved the reactivation of faults across a 700 km‐wide corridor of the Appalachian orogen. Accelerated Triassic to Late Jurassic cooling during the embryonic rift stage was concentrated along the inherited Avalonia‐Ganderia suture zone and included ~5–12 km of exhumation, erosion, and filling of rift basins. Late Mesozoic‐Cenozoic accelerated cooling during the transition from the late embryonic rift to young ocean stage is not recognized in Newfoundland but instead recorded in the Grand Banks ∼300–500 km offshore. The migration of extensional deformation from onshore to offshore domains shows that inherited faults are critical for accommodating stress during the early stages of extension but are surpassed by thermal and compositional factors as the lithosphere thins.