Significance of first-order faults in folding mechanically isotropic layers: Evidence from the Sudbury Basin, Canada

The Sudbury Basin is a non-cylindrical fold basin demarcated by the layered Sudbury Igneous Complex (SIC), the eastern part of which is transected by prominent curved faults. Folding of the SIC and adjacent rock units occurred in the brittle field and is peculiar due to its petrographically distinct, but initially mechanically similar layers. Overall, the layers are characterized by low levels of solid-state strain raising the question how the …