The Late Wisconsinan advance of the Laurentide

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The large physiographic elements of Prince of Wales Island consist of several stepped planation surfaces incised by broad meandering fluvial channels that predate formation of the archipelago. Erosion surfaces likely correlate with Sverdrup Basin Mesozoic elastic fills. Most of the island is covered by thick drift, largely till. A few subtill nonglacial deposits are likely Sangamonian. Wisconsin Glaciation left a single till sheet with three cross-cutting landscape assemblages, each recording a phase and direction of flow. Keewatin Ice flowed northwestward during phase I and was warm based except on the northern plateau; it formed megaflutes and a drumlin field. During phase 2, ice over phase I terrain was cold based but formed drumlin and ribbed moraine fields where warm based and a lateral shear moraine along the boundary, parallel to flow, between warm- and cold-based ice. During phase 3, the cold-based zone further encompassed phase 2 terrain and flow rotated suddenly by 90° and more because of capture of ice over the island by an ice stream in Gulf of Boothia. Where warm based, phase 3 and later ice formed drumlins and flutings under convergent flow across lower terrain; it formed ribbed moraine at the boundary of warm and cold-based ice at the head of a drumlin field, where flow was normal to the boundary. Phase 3 flow was beheaded before 11 ka, when the oldest end moraines were forming. The island occupies part of the tail of a zone of dispersion of shield debris, > 700 km from source, perhaps resulting from phases 1 and 2. During phase 3, debris was dispersed >120 km eastward from the island, most strongly in plumes representing ice streams. Till granule lithology best indicates dispersion. Postglacial sediments are mainly raised beaches with minor deltaic and alluvial sediment. Wetlands cap most fine glaciomarine and lacustrine deposits. A range of environmental concerns can be addressed using the surficial geology, which also provides a basis for planning mineral exploration.