SHALLOW MARINE PALEODICTYON FROM THE UPPER ORDOVICIAN GEORGIAN BAY FORMATION OF SOUTHERN ONTARIO

Two specimens, and a possible third, of the ichnotaxon Paleodictyon ar e documented from shallow-water marine strata of the Upper Ordovician Georgian Bay Formation of southern Ontario. Its occurrence indicates t hat previous suggestions of a post-Early Cambrian palaeoenvironmental retreat of Paleodictyon into deeper water require some modification. I nstead, the operative migratory process, at least to the Late Ordovici an and possibly even longer, was one of expansion and not of retreat.