Drift isopach map, Sambaa K'e candidate protected area, Northwest Territories

This publication presents a model of interpolated and minimum estimates of drift thickness overlying bedrock. Drift refers to all unconsolidated earth materials, and largely comprises glacial sediments of Late Wisconsinan age. Understanding the extent and thickness of the regional drift cover is important to studies of landslides, hydrogeology, permafrost and massive ground ice distribution, and drift geochemical exploration. Data used in the drift isopach model is principally derived from 31,171 seismic shothole drillers' logs (Smith et al., 2007; Smith and Lesk-Winfield, in press). These lithostratigraphic logs were created during geotechnical seismic exploration when holes were drilled to set explosive charges. A secondary source of data, 121 points from Janicki's (2005) formation top well database, were also included, as were 33 data points from the borehole geotechnical database (Smith et al., 2005). The Sambaa K'e Candidate Protected Area is characterized by thick (>14 m) drift mantling much of the upland region surrounding Trout Lake. The drift appears to be principally till, a heterogeneous mixture comprised of a matrix of clay and fine-silt, with minor sand, enclosing a variable but minor amount of clast and boulder material. Many of the seismic shothole drillers' log records identify what are interpreted to be two till facies, similar to that observed by Smith in field studies in the adjoining areas of British Columbia and Alberta; a lower "blue" till containing high percentages of locally quarried shale bedrock, and an upper "brown" till containing less shale and more far-travelled clastic sedimentary and Canadian-Shield igneous and metamorphic bedrock-derived sediments and clasts. Drift thicknesses south of the Mackenzie River in the northeastern regions of the Candidate Protected Area are generally thinner (<8 m) and may relate to enhanced glacial entrainment of debris under compressive, southwestward-oriented flow during glacial advance. It is likely that this area also underwent scouring by proglacial rivers along northeastward retreating ice margins during deglaciation. Purpose: Produced as part of the Secure Canadian Energy Supply Program, Northern Energy Development - Mackenzie Valley Pipeline project and Program of Energy Research and Development (PERD) Pipelines Program 1.2.5Supplemental Information: Database and GIS constructed from individual seismic shothole drillers' records, formation top well log records, and geotechnical borehole log records providing lithostratigraphic information on shallow (~<20 m) unconsolidated drift materials and bedrock. Data extents through the southern Mackenzie corridor, NWT, covering parts or all of NTS map areas 85D, 85E, 95A, 95B, 95G and 95H.

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