An Overview of the Hudson Bay Marine Ecosystem

3–1 3.0 GEOLOGY AND PHYSIOGRAPHY Chapter Contents 3.1 GEOLOGY ..................................................................................................................................................................3–1 3.2 GLACIATION...............................................................................................................................................................3–7 3.3 COASTAL FEATURES .............................................................................................................................................3–10 3.3.1 Low-Lying Coasts .....................................................................................................................................3–10 3.3.2 Cliff and Headland Coasts ........................................................................................................................3–14 3.3.3 Complex Coasts .......................................................................................................................................3–16 3.4 SEAFLOOR...............................................................................................................................................................3–17 3.5 SUMMARY ................................................................................................................................................................3–22 Chapter Figures Figure 3-1. Geological Provinces and lithology..........................................................................................................3–2 Figure 3-2. Geology ..................................................................................................................................................3–4 Figure 3-3. Glacial and nearshore features of the Hudson Bay and James Bay coasts .............................................3–9 Figure 3 4. Coastal types bordering Hudson Bay and James ..................................................................................3–10 Figure 3-5. Relief ....................................................................................................................................................3–11 Figure 3-6. Beach transects, marsh levels and Zostera beds in western James Bay .............................................3–12 Figure 3-7. Permafrost ............................................................................................................................................3–13 Figure 3-8. River drainages in the Hudson Bay watershed......................................................................................3–15 Figure 3-9. Bathymetry of Hudson Bay....................................................................................................................3–18 Figure 3-10. Bathymetry of James Bay and southeastern Hudson Bay .....................................................................3–19 Figure 3-11. Glacial surface materials.......................................................................................................................3–20 Figure 3-12. Thick sediment sequence deposited in a bedrock low just seaward of Little Whale River......................3–21 Figure 3-13. Schematic cross section showing the winter distribution of frozen ground and ice masses in the coastal zone of Manitounuk Sound .......................................................................................................3–21 Aspects of the geology, glaciation, coastal features, and seafloor that are important to the character of the marine ecosystem are described in this section. Complex details of the geological substructure and successive glaciations add little to our understanding of the marine ecology and will not be discussed. Compiled papers in the following volumes: Science, History and Hudson Bay (Beals and Shenstone [ed.] 1968), Earth Sciences Symposium on Hudson Bay (Hood [ed.] 1969), Scientific Studies on Hudson and James Bays (Martini [ed.] 1982), Canadian Inland Seas (Martini [ed.] 1986a), Quaternary Geology of Canada and Greenland (Fulton [ed.] 1989) and Sedimentary Cover of the Craton in Canada (Stott and Aitken [ed.] 1993), provide a starting point for those seeking more detailed information on regional geology and glaciations. 3.1 GEOLOGY The rock basin that holds Hudson and James bays was formed over a very long time by various geological processes. It is situated in an area that has been depressed relative to the surrounding shield regions since at least late Palaeozoic time (Coles and Haines 1982) and consists of portions of three of Canada’s geological provinces (Figure 3-1). These provinces, the Superior and Churchill provinces of the Canadian Precambrian Shield and the Hudson Platform, are distinguished from one another on the basis of the age, composition and structure of their rock strata. The older Shield rock is crystalline and often intensely deformed while the younger carbonate-dominated sedimentary rock of the Hudson Platform is mostly flat lying. These rocks form the bedrock that underlies the loose surface materials in different areas of the basin. Their composition and structure are a major determinant of the coastal physiography, surface soil and offshore sediment, bathymetry, and local physical and biological oceanography of the Hudson Bay marine ecosystem. 3–2 Figure 3-1. Geological Provinces and lithology (from Douglas 1973). The crystalline rock of the Superior Province formed first and underlies the entire basin (Whitmore and Liberty 1968; Bostock 1969; Douglas 1972, 1973; Brooks 1980; Donaldson 1986; Mortensen and Ciesielski 1987). It constitutes the bedrock of the Québec coast south of Korak Bay, except in the area of Richmond Gulf (Lac Guillaume Delisle) and west of the Nottaway River, and the bedrock beneath the eastern half of James Bay. Elsewhere in the basin it forms a sialic crust beneath the younger sedimentary, metamorphic and volcanic rock of the Churchill Province and the sedimentary rocks of the Hudson Platform. North of Rivière de Castor the rock of the Superior Province forms plutonic belts, to the south basement (Figure 3-1). The plutonic rock is mainly intensely deformed and metamorphosed migmatic and granitic gneiss including undifferentiated older and younger rocks, and granulites; the basement rock is mainly deformed and/or isotopic age modified migmatic and granitic gneiss and undifferentiated older and younger rocks. These rocks formed during the Archaean eon, 4000- 2500 million years before present (MYBP). The crystalline rock of the Superior Province formed first and underlies the entire basin (Bostock 1969; Whitmore and Liberty 1968; Douglas 1972, 1973; Brooks 1980; Donaldson 1986; Mortensen and Ciesielski 1987). It constitutes the bedrock of the Québec coast south of Korak Bay, except in the area of Richmond Gulf and west 3–3 of the Nottaway River, and the bedrock beneath the eastern half of James Bay. Elsewhere in the basin it forms a sialic crust beneath the younger sedimentary, metamorphic and volcanic rock of the Churchill Province and the sedimentary rocks of the Hudson Platform. North of Rivière de Castor the rock of the Superior Province forms plutonic belts, to the south basement (Figure 3-2). The plutonic rock is mainly intensely deformed and metamorphosed migmatic and granitic gneiss including undifferentiated older and younger rocks, and granulites; the basement rock is mainly deformed and/or isotopic age modified migmatic and granitic gneiss and undifferentiated older and younger rocks. These rocks formed during the Archaean eon, 4000-2500 million years before present (MYBP). Younger crystalline rock of the Churchill Province overlies the older rock of the Superior Province throughout much of the basin. It constitutes the bedrock of the Québec coast north of Korak Bay and in the Richmond Gulf area; the Ottawa, Belcher and Nastapoca islands; the west coast of Hudson Bay north of the Knife Delta (58°54'12"N, 94°41'52"W) in Manitoba; and the bedrock under the coastal waters in these areas, including most of southeastern Hudson Bay. There are exposed meetings of the Superior and Churchill provinces at the margins of the Cape Smith Fold Belt and Richmond Gulf Embayment. Unlike the Superior Province, the volcanic- sedimentary associations in the Churchill Province occur in linear and curvilinear fold belts in which the sedimentary rocks are generally more abundant than are the volcanic rocks (Donaldson 1986). The Churchill Province consists mainly of basement rocks of Proterozoic age (Aphebian Era 2450-1700 MYBP), including deformed and/or isotopic age modified migmatic and granitic gneiss and undifferentiated older and younger rocks, except in the Cape Smith Fold Belt and Kaminak Subprovince (Whitmore and Liberty 1968; Taylor 1982; Aylsworth et al. 1986; Donaldson 1986). The Cape Smith Fold Belt extends northeastward from the Ottawa Islands (Coles and Haines 1982) to Cape Smith and then inland across Ungava Peninsula (Taylor 1982). It has a series of northeastward-trending thrust faults, and is composed of deformed or partly metamorphosed sedimentary and volcanic rock of Proterozoic age. The Kaminak Subprovince underlies the coast and adjacent waters between Arviat and Rankin Inlet (Douglas 1972; Donaldson 1986). It is a belt of deformed and metamorphosed volcanic and sedimentary rocks, mostly of Archaean age. Three geological subdivisions of the Churchill Province underlie southeastern Hudson Bay, the Richmond Gulf Embayment, Nastapoca Homocline, and Belcher Fold Belt.

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