Update: see here papers a decade later that point also to precambrian terranes.
My 1982 M.Sc. thesis, Regional cross section of the Southern Province adjacent to Lake Huron, Ontario: implications for the tectonic significance of the Murray Fault Zone (ResearchGate) proposed a plate-tectonic (Wikipedia) setting around 1.9 billion years ago, in the Proterozoic (late Pre-Cambrian). I presumed there was another buried land mass south of what I called the Manitoulin Island Discontinuity. While plate tectonics was well established in the later Phanerozoic (Wikipedia) record, it took a lot longer to be accepted earlier in the geologic time scale with lot scanter rock record to go by (more at the bottom).
