SOUTHWESTERNMOST COAST OF JAMES BAY

INTRODUCTION

The southwesternmost part of James Bay is affected by several north-flowing large rivers that input much, relatively warm freshwater into a shallow sea, freshening it up (Fig. JBS 1; Martini et al., 1980b). The area is located in the sporadic permafrost area (Fig. JBS 2). It also contains the largest settlements of the region: Moosonee and Moose Factory at the head of the Moose River (MR) estuary (Fig. JBS 1).

The southwestern coast of James Bay lies in the humid, subarctic climatic zone of Albany (Chapman and Thomas, 1968).  It is classified under the Köppen sys­tem as Dfc (humid microthermal subarctic climate).  The average annual tempera­ture is -1°C, the mean annual minimum temperature is -4l°C.  The winters are very cold with a January temperature averaging -16°C, and the summers have hot days with a mean daily maximum for July of 23°C.  Average annual precipitation is approximately 650 mm of water with 241 cm of this being snowfall.  The last date of frost is in mid June and the mean date of the first frost is in early September.

Ice conditions in James Bay vary from year to year and from location to loca­tion depending on the prevailing winds during break-up (Markham, 1988; Canadian Ice Service, 2002).  Normally the freeze-up begins during late fall and is completed by the end of December. Satellite imagery indicates that in 1968, for example, the central part of the bay was freed from ice between June 12 and 17 – some reattachment occurred only to the west of Akimiski Island (AK) on June 27 (Clerc, 1969) – and all of James Bay and most of Hudson Bay were free of ice by July 16.  On average, most of the coast of James Bay is protected by ice cover for at least 6 months of the year, and is otherwise affected by sea-ice for approximately two to three months more during the freezing and melting seasons.

Atmospheric circulation over the Hudson Bay Lowland (HBL) is affected predominantly by a counter-clockwise movement of air related to a low pressure vortex over south Greenland during the winter, and over Baffin Island and Ungava Bay during the summer, and to a high pressure vortex over the Macken­zie Basin (NW Canada) in winter, and the Arctic islands in the summer (Thompson, 1968). Wind direction (measured in Moosonee) is variable with predominance from the western quadrants throughout the year, and very strong northeasterly winds being important in the spring and summer (Environment Canada, 1975). The average wind speed ranges from approximately 16 km/hr to 9 km/hr with a maximum observed hourly speed of 69 km/hr for a northerly wind, and probable maximum gusts of maximum hourly speed of 98 km/hr.

Salinity of surface waters of southern James Bay during August is generally low, less than 10‰, and surficial water temperatures can be as high as 9°C in late August. The salinity increases in value with depth reaching a value of 24‰ in south central James Bay at a depth of 50m where temperatures of -1.2°C have been measured (most of the water depth in the southern part of the Bay is less than 20 m) (Barber, 1968). Salinity and other water qualities of southern James Bay are much affected by the fresh, warmer water input from rivers.  Such input has been estimated to be approximately 6.96 x 10 m /sec, of which 23% comes from rivers along the western side of the bay.  By applying a two-layer model, "a value of 10 months was estimated as the flushing time of James Bay" (El-Sabh and Koutitonsky, 1974, p. 10)
　

The tides are semi-diurnal and range in height from 0.7 to 3m at the mouth of the Moose River (Environment Canada, 1977).  Storm surges occur and have a drastic effect on the coasts. Marine currents of the Bay are slow, generally less than 1 knot, and the overall direction of circulation is counter­clockwise (Fig. JBS 2).

Coastal features

The cost has been analyzed along several transects (Figs. JBS 3, 4; Martini and Protz, 1978; Martini, 1981). The followings are the principal landscape units of the southwest coast of James Bay (Figs. JBS 1, 5).  (1) Coasts characterized by uniform, gentle offshore slopes of approximately 0.5m/ km (Fig. JBS 5).  (2) Wide bays receiving large amounts of freshwater from rivers such as the Harricanaw (HA) and Moose (MR) rivers (Figs. JBS 1, 4, 5 (HBE), HBE 1).  (3) Wide, low promontories that expose Paleozoic carbonate bedrock, Pleistocene tills, or accumulations of erratics.  Erosional (half-moon bays) and depositional (spits) landforms develop on their southern downdrift sides (Figs. JBS 4 (HBW), HBW 1).  (4) Narrow promon­tories that extend several kilometers on the shallow shelf and may develop transverse ridges (Figs. JBS 4 (LR), LR 1), some of which have characteristic seaward bifurcations such as at Puskuake Point (Figs. JBS 4 (PP), LR 2).  Between Longridge Point (LR) and Nomansland Point (NM) sets of these promontories bound narrow deep bays (Figs. JBS 4, LRB 1).  (6) Sequences of beach ridges and spits that build parallel to the main coasts (Figs. JBS 4, 5, HY 1).  (7) Wide tidal flats, some of which are characterized by shallow sinusoidal sand waves (Figs. JBS 4 (GP, LRB) , JBS 5(GP, LRB), GP 2, LRB 2).  (8) In inland areas some coastal features are obscured by growth of vegetation and development of wide wetlands.  Some features, such as promontory complexes (Fig. HBW 1), longitudinal beach ridges, and chevron beach ridges (a landform characterized by a combination of transverse and longitudinal ridges) (Figs. JBS 5 (LRB), JBS 6, LR 3) are recognizable because they support well-developed forests.

The material and biological characteristics of these environments are the followings. (1) Large boulders, pebbles, and sand of local origin, having a predominantly calcareous (limestone and dolostone) composition.  Calcareous shale and siltstone become locally important near outcrops of Paleozoic red-beds such as at Cockispenny Point (Figs. JBS 4 (CCS), CCS 1).  (2) Precambrian igneous, metamorphic, and a few sedimentary boulders, pebbles, and sandstones that have been transported into this area by glaciers, presumably from exposures in Quebec. (3) Clays, derived both from local tills and from the widespread sub­stratum of the marine clay of the early postglacial Tyrrell Sea, cover most of the coastal area. (4) Clay, silt, and predominantly organic suspended material are transported into the bay by the larger rivers and creeks that drain inner wetlands and coastal marshes.  (e) A restricted faunal assemblage, with notable microforms such Macoma balthica and Hydrobia minuta (Martini and Morrison, 1987), is found in the tidal flats and marshes, and mollusks are important in the modification of sedimentary deposits. They also constitute a source of food for migratory shore birds.  The floral assemblage ranges from the Zostera marina (seagrass) zone in the lower parts of the tidal flats to various floral assemblages of the high tidal flats, coastal marshes, and inland fens, bogs and forests.

Several agents act upon these coastal environments and materials as follows. (1) Glacial isostatic rebound of the land began approximately 8000 ¹⁴C yr BP at a rate of about 300 cm/100 yr, and still continues at a reduced rate of approximately 70 to 100 cm/100 yr. (Webber et al., 1970). (2) Marine semi­diurnal tides generally have a low range (0.7 m to about 1.5m) reaching a maximum at some localities of 3 m. The tides can rework the surface of sandy, silty tidal flats, and carry much fine material onto high tidal flats and lower marshes.  (3) Wind generated waves form in the open bay during storms can sweep tidal flats and rework sands and pebbles, piling them up locally on coastal ridges.  However, this is considered on the whole a low energy coast.  (4) A slow but apparently regular marine current moves in an anticlockwise direction. In bays, such as Hannah Bay (HA, JBS 1), local currents and gyres develop which redistribute or trap sediments along their coasts.  (5) Sea ice covers the coast for approxi­mately six months of the year, protecting it.  However, during freeze-up and thaw ice floes raft much material along the tidal flats, and push and scour the sedimentary surfaces.  (6) Wind may locally and for short periods of time rework and reshape sediments of upper parts of tidal flats rapidly moving thin sheets of water. (7) The cold climate of this coast sustains freeze-and-thaw processes of weathering, especially for susceptible rocks such as bedded limestone and dolostone.  (8) The physical and biochemical action of organisms in the tidal flats and inland areas, combined with other types of chemical weathering, modify the primary characteristics of parts of the mineral deposits.  Soil profiles develop and organic deposits become increasingly impor­tant inland.

The response of the landscape to these processes generates a variety of sedimentary deposits that singly are not unique to James Bay, but whose associa­tions characterize regressive coastal sequences of a cold inland sea. These sequences may help not only in predicting the response of the environment to natural and man-made changes, but also in interpreting the history and paleogeography of ancient deposits.  (1) Bouldery and pebbly tidal flats, occasionally bounded landward by bouldery beach ridges, develop near outcrops where the bed­rock is shattered by frost action, and near till or accumulations of boulders that are being reworked by tides and storm waves.  These deposits are not very common.  (2) Near wide promontories and in downdrift sides of narrow transverse ridges, tidal flats develop that are either erosional or have very low rates of deposition. They are usually underlain by shattered soft bedrocks, such as red-beds of Cockispenny Point (Figs. JBS 4 (CCS), CCS 3), or by clays of the early postglacial Tyrrell Sea. Recent sediments are ice-rafted onto them and are reworked by waves and longshore currents. Ice-drift generated features characterize these tidal flats.  Their sedimentary successions are composed of an upper thin layer of coarse pebbly, poorly sorted sand, and by a basal reconstituted coastal diamicton that has been formed by mixing of coarse ice-rafted material with the underlying marine clay (Fig. CCS 17).  Much of the material that is removed from the intertidal areas is piled up on well-developed, high beach ridges. Marshes, if formed at all on these coasts, are very narrow and discontinuous.  (3) Wide, poorly drained tidal flats and marshes form near the mouths of large rivers.  They are characterized by a relatively low rate of depo­sition, but the ubiquitous presence of plants also in many parts of the intertidal flats, allows trapping of suspended silt and organic matter. Fining-landward, grain-size trends develop.  The marshes have typical particle-size successions that fine upward, as well as characteristic organic-rich, silty laminations.  (d) Wide sand flats develop in protected bays, in northern, updrift sides of long, narrow promontories, and on those coasts whose orientation prevents breaking of the open-sea storm waves directly onshore (Figs. JBS 4 (LRB), LRB 1). These tidal flats have thick sedimentary successions (up to 2 m thick), they may develop sand undulations (sand waves) in their intertidal zones to adjust the slope to prevailing wave conditions, and most of them have wide coastal marshes.  The steeper, narrower sand flats can develop storm beach ridges, the wider ones grade imperceptibly from the open flats, to high tidal flats, to fully vegetated marshes (Martini, 1991).  Some of these tidal flats are affected strongly by ice-drift (Martini, 1981b), which leaves its major legacies in the pitted pool pattern, initiated by ice scouring in the lower marshes and high tidal flats and modified after rebound, by plant growths, and action of birds (feeding) and other organisms (Figs. NPD 10, NPD 11).  Good sedimentary successions develop in these tidal flats. They show a lateral shoreward fining in grain size, homogeneous vertical sandy and silty accumulations in sand flats, with an occasional poorly developed upward coarsening, and with an upward-fining well-developed in high tidal flats and marshes (Figs. LRB 3, LRB 5).  Beach ridges generally are composed of alternating sand, granules, and pebbly sands that reflect recurring storm con­ditions (Figs. NPD 21, NPD 23).  The pebbles are commonly fine and of carbonate composition.  The sand flats constitute one of the most important environments of the coast because they contain regressive sedimentary sequences that can be preserved and recognized in ancient deposits, and because they constitute the feeding and breeding grounds of a variety of migratory birds.  (5) The close association of characteristic sedimentary sequences with landscape, and the possibility of recognizing one (through textural analysis) or the other in the interior lands (Hudson Bay Lowland), allow mapping of the mineral substratum of the wetlands and a better understanding of peat dynamics.