The Late Ordovician fauna of the northern Hudson Bay Lowland, Manitoba, Canada, consisting of three stromatoporoid species (1 new), 41 coral (11 new and 2 new genera), 8 gastropod (1 new), 56 cephalopod (21 new and 1 new genus), and 1 graptolite species are described and in part illustrated. Brachiopods are listed only. This fauna was obtained from five formations consisting mostly of fossiliferous dolomitic limestone 300–400 feet thick. In ascending order these are: the Portage Chute and Surprise Creek formations of the Bad Cache Rapids Group; the Caution Creek and Chasm Creek formations of the Churchill River Group; and the Red Head Rapids Formation. The Bad Cache Rapids Group, which rests on peneplaned Precambrian, is correlated with the Red River Formation of southern Manitoba, the Churchill River Group with the Stony Mountain Formation, and the Red Head Rapids Formation questionably with the Stonewall Formation. The faunas indicate a close temporal relationship between the Bad Cache Rapids and Churchill River groups. The latter is considered Richmondian and in part Gamachian. A Late Ordovician age is thus also suggested for the Bad Cache Rapids Group and hence for the coeval Red River Formation.

Abstract The Hudson Bay basin is a cratonic basin situated in the central part of the Canadian Shield. Its basement is composed of crystalline rocks belonging to the Superior Province (2.9 Ga) in the southern and central part and to the Churchill Province (1.6 to 1.9 Ga) in the northern part. The eastern part of the basement of the basin has been affected by the Hudsonian Crogeny. The Hudson Bay basin is filled with Paleozoic sediments with a thickness of at least 1,576 m (5,170 ft) proven by drilling in the central part of the basin. The subsidence and sedimentation rates were moderate with several periods of uplift and erosion during the Paleozoic. The Mesozoic is absent in the Hudson Bay basin. The Paleozoic sedimentation, typical of a cratonic basin (Figure 1), started in Upper Ordovician time with basal orthoquartzitic sandstones, and continued with platform-type limestones and dolomites with some anhydride and salt (Bad Cache Rapids and Churchill River Groups). Oil shales 2 to 8 cm (1 to 3 in) thick are interbedded in the upper part of Bad Cache Rapids group carbonates outcropping on Southampton Island. A few similar but thinner interbeds, in a similar position, occur in carbonates in the Kaskattama well also onshore in the Hudson Bay Lowlands.