Cretaceous strike–slip displacement along the Porcupine fault system and potential links to the opening of the Canada Basin

Tectonic models for the evolution of the Canada Basin of the Arctic Ocean posit Jurassic–Cretaceous counterclockwise rotation of the Arctic Alaska terrane away from the Canadian Arctic Islands, translation along a strike–slip fault system, or some hybrid combination of the two. Here, we present evidence for post-Devonian deformation within the Porcupine fault system of northern Yukon and Alaska, which forms the southeastern boundary of the Arctic Alaska terrane. Neoproterozoic–Cretaceous strata exposed within the fault zone record polyphase deformation related to strike–slip displacement. Muscovite 40 Ar/ 39 Ar data from two samples collected north of the Porcupine River produced plateau or plateau-like segments at ca. 342–367 Ma and younger steps at ca. 105 Ma, consistent with initial cooling after emplacement of the Upper Devonian Old Crow plutonic suite and later Cretaceous–Cenozoic partial resetting. In contrast, samples from within the main strand of the fault system yield complex spectra with single steps as old as ca. 1779 Ma, highlighting contrasting thermal histories across it and post-Late Devonian truncation of the Old Crow plutonic suite. The timing of Mesozoic deformation is better constrained by U/Pb dating of calcite veins within the fault system, which yield an age of ca. 121 Ma. Coupled with field observations of unambiguous strike–slip related deformation within the Porcupine fault system, these geochronological data are consistent with translational or hybrid models for the opening of the Canada Basin.