The Cygnet-Snelling Fault Zone on Kangaroo Island is a fundamental structure that both influenced sedimentation during the Cambrian, and refined the boundary between major tectonic provinces during the Delamerian Orogeny. It is coincident with the southeastern margin of the Gawler Craton. Shallow depths to basement beneath the north coast sequences on Kangaroo Island, together with gentle deformation of the Cambrian cover, imply that thi s region is synonymous with the Torrens Hinge Zone. The margin of the Gawler Craton is revised southwards beneath Kangaroo Island, and eastwards to just offshore of Fleurieu Peninsula.