The Phanerozoic rocks of Moose River Basin are separated from those of Hudson Bay Basin by a northeast-trending Precambrian basement high, the Cape Henrietta Maria Arch (Fig. 8.1; see also Fig. 7.1). Because of the close similarity of facies and faunas, both basins were almost certainly connected with the Williston, Michigan, and Appalachian basins to the south during various intervals of Paleozoic time. The character of Ordovician and Silurian outliers on the Canadian Shield (Caley and Liberty, 1957), at Clearwater Lake (Kranck and Sinclair, 1963), Waswanipi (Clark and Blake, 1952), Lake Timiskaming (Hume, 1925), Mattawa, Lake Nippissing, and others, tends to support this hypothesis.

The northern boundary of Hudson Bay Basin is Bell Arch, trending northwestward through Southampton Island and bordering Foxe Basin of the southeastern Arctic Platform (see Fig. 7.1). The Phanerozoic rocks of Hudson Platform are separated from Williston and Elk Point basins to the southwest by Precambrian rocks of Severn Arch. To the south, Fraserdale Arch separates Moose River Basin from St. Lawrence Platform and Michigan Basin.

A basin concept for the offshore regions of Hudson Bay, inferred from sea-magnetometer profiles, was firmly established by Hood (1964). On the basis of refraction seismic data, Hobson (1964a, b) confirmed a basin of major proportions beneath Hudson Bay. Seismic profiles suggest that about 2000 m of Phanerozoioc strata are present in Hudson Bay Basin, and 600 to 800 m in the deeper parts of Moose River Basin.

Two structural provinces of the Canadian Shield, Superior and Churchill, border and