POST-NECKING RIFT REACTIVATION IN THE PROXIMAL DOMAIN DRIVEN BY CAMP MAGMATISM, FUNDY BASIN, CANADA

Rifted continental margins record distinct phases of tectonic extension that include a stretching phase, necking phase, in some cases, hyperextension, and finally break-up. The necking phase is critical for the success of a divergent plate boundary, and the conventional paradigm suggests a cessation of faulting in the proximal domain as tectonic strain migrates away from the proximal domain border faults into the rift axis. Here, we investigate source-to-sink dynamics, tectonic strain evolution, and magmatism during progressive continental rifting of the SE Canadian Margin with a focus on the Fundy Basin located within the proximal domain. The Triassic and Jurassic syn-rift sedimentary and volcanic rocks of the Fundy Basin provide a ~35 mya record of landscape and sediment routing evolution spanning diffuse stretching, crustal necking, and late-stage magmatism culminating in continental breakup. We present detailed new detrital zircon and detrital apatite U-Pb provenance data from the Carnian to Early Jurassic syn-rift sedimentary rocks and provide paleodrainage reconstructions and a new tectonic model for the syn-rift evolution of the SE Canadian Margin. The results show source linkages to the Cambrian Meguma Terrane, Devonian South Mountain Batholith, and Late Devonian to Carboniferous sedimentary cover, and exhibit marked provenance shifts indicative of two major syn-rift paleodrainage reorganizations. The first occurs in the early Norian middle syn-rift phase and is marked by an unconformity that signals a decrease in syn-rift subsidence within Fundy Basin and a shift to localized extension in the off-shore Scotian Basin. Collectively, this evidence points to a Norian paleodrainage reconfiguration that resulted from the uplift and unroofing of the Nova Scotian hinterland due to strain localization to the east in the necking domain. A second provenance shift and paleodrainage reconfiguration occurred in the Jurassic late syn-rift succession due to the Central Atlantic Magmatic Province (CAMP) magmatism. Seismic imaging of post-necking units in the Fundy Basin shows fault-bounded wedge geometry, lacking the typical saucer-shaped sag geometry. These new data provide compelling evidence for the reactivation of rifting in the proximal domain during the post-necking phase of progressive rifting and continental breakup.