Some infalling large meteors are thought to break up into many fragments, resulting in clusters of craters over an area. Ontario has been subject to glaciation, but the subsurface structure should remain. A test would be the presence of ceosite, or shocked rock. Some drilling and rock sampling would settle the issue.
My first thought as I started to read the post was Carolina Bays. However, what is shown here is round, not eliptical. On the other hand, if Firestone et al. are right, that the boloid struck above Eastern Canada, perhaps these represent a direct rain down, or close in splatter traces. Does anyone have photos further West or Northwest on this phenomenon, possibly shading into a more eliptical, oriented configuration?