A GIS dataset of surficial geological features for the Fort Norman map area (96C), Northwest Territories

The study area incorporates the Fort Norman (NTS 96C) map area, and extends from the Franklin Mountains/McConnell Range in the east to the Canyon Ranges of the Mackenzie Mountains in the west. The Mackenzie River flows through the map area from the southeast to the northwest. The surficial geology of the area is characterized by a discontinuous veneer of mostly till and/or glaciolacustrine sediment. Although glaciofluvial sediments are not widespread, they do form terraces along the Mackenzie, Keele, Redstone and Great Bear rivers. Minor eskers, glacial lake shorelines and kames are found in the plain area which extends between 10 and 40 kilometers on either side of the Mackenzie River. The plain is blanketed by surficial sediments and is bordered by the Franklin Mountains/McConnell Range to the east and the Canyon Ranges to the west. Bedrock in the mountainous terrain and part of the northern plains is Proterozoic shale and Carboniferous to Devonian sandstone and carbonates. The Plains east of Franklin Mountains are underlain by Cretaceous sandstone and shale and Tertiary sandstone and conglomerate. The study area is located in a region of discontinuous permafrost. Debris flows, triggered by forest fires, commonly expose the underlying permafrost, leading to the development of retrogressive thaw flow slides. This process is particularly prevalent along glaciolacustrine and glaciofluvial terraces adjacent modern rivers. Mudflows and rotational slides affecting surficial materials and/or bedrock are also commonly found along rivers. The largest scale of mass wasting noted in the area occurs at several sites where landslides, likely triggered by seismic activity in the mountains, have in the past blocked valleys forming temporary lakes and rerouting streams. Active karst, developed in regional carbonate bedrock, is seen in solution and collapsed sink-holes, commonly found in mountainous/hilly terrain as well as in the plain area northwest of the study area. Some karst dolines show evidence of periodic flooding by groundwater, and deep solution channels cut along the southern slopes of Franklin Mountains are interpreted to indicate initial solutional weathering by glacial meltwater. Areas of extensive glaciolacustrine sediment, up to 80 meters thick, occupy the central part of the Fort Norman map area. They were deposited in glacial Lake Mackenzie around 10.5 ka BP when the Laurentide Ice Sheet had retreated eastward to the McConnell Range and southward to the mouth of the Blackwater River. Glaciofluvial deltas built into the lake presently sit as raised sandy and/or gravel deltas alongside upper shorelines around 300 m above sea level*. Glacial Lake Mackenzie drained northwest along the mountain front in two main stages: 1) Moose Nest Creek-Summit Creek, and 2) Red Dog Creek-Stewart Lake-Tate Lake-Little Bear River. Various deltas, shorelines and outlet channels are shown in the surficial geology of the Fort Norman map area. * Value not corrected for isostatic rebound.

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