Quaternary Geology of the Tuktoyaktuk Coastlands, Northwest Territories

Abstract

The Tuktoyaktuk Coastlands consist of a thick wedge of Pleistocene marine and fluvial sediments that contain much ground ice and have been modified by glaciation and thermo karst. East of Nicholson Peninsula the Stanton Sediments, consisting of a basal clay member, lower complex member, thinly bedded member, and an upper sandy member, represent Middle Pleistocene deposition in marine and alluvial environments. West of Nicholson Peninsula, Kendall sediments and Hooper clay of marine origin underline the Kidluit Formation of alluvial origin. Kidluit Formation is overlain by the Kittigazuit Formation, a thick fine grained deltaic sand of likely glaciofluvial origin. Northwesterly moving continental (Laurentide) ice defined a glacial limit on Cape Bathurst peninsula around unglaciated terrain to the north during the Mason River Glaciation of Middle Pleistocene age. Major strandlines marking marine limits were formed in this area during the Horton and Harrowby marine episodes (seas) of Middle Pleistocene age. Also in this region low marine benches, some inset into glaciated terrain, are likely Sangamonian in age as they contain organicbearing deposits (Ikpisugyuk Formation) indicative of interglacial climate. Northwesterly flowing continental ice again covered most of the area during the Toker Stade of Early Wisconsinan age. Sediments were glacially deformed in peripheral areas; till (Toker Point Member) and outwash (e.g., Turnabout Member, Garry Island Member, and Cape Dalhousie Sands) grading to relatively high sea levels were deposited. During the likely equivalent Franklin Bay Stade, westerly moving ice from Amundsen Gulf impinged on the eastern coast of Cape Bathurst peninsula. Ground ice, common to most of the area, was formed during deglaciation. During the Sitidgi Stade of Late Wisconsinan age, Laurentide ice persisted in the southern Mackenzie Delta and Sitidgi Lake areas and deposited till (Sitidgi Member). Sediments of a large proglacial valley train (Portage Point Sands) and a large proglacial lake (Eskimo Lakes Member) formed in the unglaciated Eskimo Lakes area during this stade. Extensive thermokarst activity during the Holocene produced thermokarst deposits (Parsons Lake Formation) and resulted in the formation of the ice-cored topography. During Late Wisconsinan and Holocene, valleys that had been eroded during the Wisconsinan were drowned and filled with thick fine grained alluvium. The Mackenzie Delta, consisting mainly of fine sand and silt (Aklavik Formation) and characterized by many thermokarst lakes, was formed. Rapid retreat of exposed coastlines has occurred. Periglacial processes and minor eolian activity and peat accumulate on continued throughout the Holocene. Ground ice and subsidence resulting from its thaw represent major hazards to development as does flooding of low-lying areas. Sand fill is a common resource, but coarser aggregate is only locally available.