Emergent coasts of Akimiski Island,James Bay,Northwestern Territories,Canada: geology,geomorphology, and vegetation |
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| Authors: | IP Martini WA Glooschenko |
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| Institution: | 1. Department of Land Resource Science, University of Guelph, Guelph, Ont. N1G 2W1 Canada;2. Environment Canada, CCIW, Burlington, Ont. L7R 4A6 Canada |
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| Abstract: | Akimiski Island contains good examples of emergent coastal landscapes of a cold mesotidal inland sea. The Paleozoic reefal trend of the Attawapiskat Formation dictated the overall shape and the main structure of the island. Differential erosion and deposition by Pleistocene glaciers have fluted the island in a north-south direction. That surface was later modified by emergent landforms developed in the last 3500–4000 yrs.The modern steeper southern area reaches an elevation of 60 m approximately 3 km inland from the southern shoreline, and contains well-developed sandy and gravelly longitudinal beach ridges and spits, now inactive and covered by a lichen-rich taiga (boreal forest). The flatter, northern part of the island shows a wide transition between the primarily erosional, sand-starved, coastal marshland and the inland organic-rich fens. Partially paludified longitudinal and transversal beach ridges subdivide those northern flat wetlands forcing a straight course to the north-flowing streams.The vegetation zonations of the marshes are as varied as the coasts, facing different oceanographic conditions. Longshore and tidal currents affect the western and southern coasts greatly. Tides, waves and sea ice affect the others more. The marshes resemble those of the mainland in having well-defined Puccinellia phryganodes lower marsh, Carex subspathacea upper marsh, and peat-forming coastal fens. Some components of the marshes of the island, such as isolated mounds with vegetation minisequences, incipient permafrost features generated by seasonal frozen ground conditions, and intense grazing by large populations of geese, are typical of cold settings, more commonly found along mainland coasts farther to the north in James Bay and Hudson Bay. |
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