Southeastern Hudson Bay Research Articles

Thecate Hydroids from the Shelf Waters of Northern Canada

Based largely on collections from the Calanus–Salvelinus expeditions, 54 species of thecate hydroids were identified from the shelf waters of northern Canada between northeastern Newfoundland and the Alaska–Yukon border. Common species included Halecium muricatum, Calycella syringa, Campanularia integra, C. speciosa, C. volubilis, Gonothyraea loveni, Filellum serpens, Lafoea gracillima, Sertularella polyzonias, S. tricuspidata, Sertularia schmidti, and S. similis. Halecium groenlandicum, H. scutum, Cuspidella procumbens, Calycella gracilis, and Sertularia schmidti are new records for North America; Ptychogena lactea is previously known from this continent only as the medusa. Twenty-two species are reported in northern Canada for the first time, bringing to 71 the number of thecate species recorded from the region. Nearly half of the 71 species recorded are circumpolar in distribution, and over two-thirds transgress both arctic and subarctic zones.Most samples had a paucity of hydroids, particularly those from the high arctic. Collection records indicate that the most favourable regions for hydroids in northern Canada are the Strait of Belle Isle, eastern Ungava Bay, eastern Hudson Strait, northern and southeastern Hudson Bay, Foxe Channel, and northern Foxe Basin.

Post-glacial uplift and substrate age at Cape Henrietta Maria, southeastern Hudson Bay, Canada

As a basis for future ecological and biogeographical studies, the post-glacial emergence history of Cape Henrietta Maria was required. This was obtained by fitting a post-glacial emergence curve to a number of radiocarbon dated marine strandlines of known elevation. Analysis shows that the elevation of lower samples is critical for a reasonable prediction of higher relative sea levels. This emergence curve suggests that during the last 1000 y uplift has been about 1.2 m per century. Extrapolation to likely dates of deglaciation (8000−7000 BP) indicates a maximum marine inundation of > 300 m. The current rate of uplift, and the hypothetical elevation of the marine limit are the highest estimations to date for eastern and arctic Canada and support the hypothesis that a center of uplift and ice-loading is situated in southeastern Hudson Bay and northern James Bay. The derived emergence curve was used to construct an isochrone map of Polar Bear Park, in eastern northern Ontario. This map provides the basis for future biological studies of community migration and succession and demonstrates that the uplift curve is a useful chronological tool.

Present and postglacial rates of uplift for glaciated northern and eastern North America derived from postglacial uplift curves

Average rates of postglacial uplift reach a maximum value of nearly 4 m 100 y−1 over southeastern Hudson Bay, and another high cell, with rates of about 2.5 m 100 y−1, lies between Bathurst Inlet and Southampton Island. Current rates of uplift are underestimated if exponential curves are fitted solely to dated raised marine deposits without considering the amount of future recovery. Rates of rebound are, instead, derived from A/t where A is uplift in the first 1000 y since deglaciation, and t is time since deglaciation. For the northwest margin of the former ice sheet coefficients of determination for rate of uplift, at specific times, as a function of distance are [Formula: see text]. Maps of rates of uplift for northern and eastern North America are presented for 8000 y B.P., 6000 y B.P. and the present day. They reveal the existence of three uplift centers and show that rates of uplift declined from a maximum of 10 to 12 m 100 y−1, immediately following deglaciation, to a current maximum of about 1.3 m 100 y−1. Agreement is satisfactory when calculated rates of uplift are compared with those derived from geological observations, radiocarbon dates, and from water-level records. A final map shows isochrones on the uplift rate of ~1 m 100 y−1. The rate dropped to this value about 10 000 y ago on the outer northwest and southeast coasts, whereas the value might not be reached for another 2000 y in southeastern Hudson Bay.

Radiocarbon Date from the Lake St. John Area, Quebec

A radiocarbon age of 8680 +/- 140 years found for fossil marine shells in the Lake St. John area, Quebec, shows that marine submergence there apparently preceded the "Tyrrell Sea" in southeastern Hudson Bay, but followed the Champlain Sea episode in the St. Lawrence Lowlands.

The Origin of Diamonds in Drift of the North Central United States

Diamonds found in Wisconsin drift in Ohio, Indiana, Michigan, and Wisconsin are proposed to have been carried south from an ancient meteorite crater at present outlined by the Nastapoka island arc in southeastern Hudson Bay. Following meteorite impact, brecciation extended to a depth of about 150 km., and fragments of this mantle-rock breccia, enclosing diamonds, are inferred to have been brought to the surface in a central uplift similar to those found in lunar craters. Following the crater's formation, sediments filled it and were lithified, but these rocks are thought to have slid by gravity from the central part of the crater as it rose isostatically, permitting the diamond-bearing rocks to be re-exposed.