Glacial geology of western Hudson Strait, Canada, with reference to Laurentide Ice Sheet dynamics

摘要

Hudson Strait is a large marine trough that connected the marine-based interior of the Laurentide Ice Sheet with the ocean. Field investigations of the glacial geology of western Hudson Strait have helped to define the role of the strait in Laurentide Ice Sheet dynamics. In general, ice converged on western Hudson Strait from the north, west, and south. Upon reaching the strait, ice flowing from Foxe and Ungava Peninsulas turned eastward within less than 10 km of the coast to parallel eastwardly flowing ice in the strait. Glacial erosion of western Hudson Strait is identified as slight. The texture, carbonate content, pH, and the presence of several types of erratics distinguish till on Nottingham, Salisbury, and Mill Islands in western Hudson Strait from till on southern Foxe Peninsula and northern Ungava Peninsula. Till on the islands is characterized by higher pH and higher proportions of silt, clay, and carbonate than till on either adjacent peninsula. In addition, the presence of red sandstones, porphyritic intrusives, stromatolites, omarolluks, and iron formation are restricted to the islands with few exceptions that can be explained by ice rafting. Carbonate is present in the pebble and boulder fractions of till on Foxe Peninsula and in all fractions of till on the islands but is absent from till on Ungava Peninsula. These data suggest that ice from distant and widely distributed source regions affected western Hudson Strait and along with evidence for a rapid change in ice-flow direction along the margins of Hudson Strait suggest that the strait was occupied by a relatively fast-moving ice stream that had a substantial impact on the interior of the ice sheet through downdraw.