Drift isopach, till isopach, and till facies reconstructions for Northwest Territories and northern Yukon

Unconsolidated sediments, collectively referred to as "drift," blanket much of the terrain in the Mackenzie corridor, Mackenzie Delta and adjoining regions of petroleum exploration and development in Northwest Territories and northern Yukon. The drift cover is dominantly till, but may also include significant regional and localized accumulations of glaciofluvial, glaciolacustrine, and glaciomarine sediments as well as post-, and pre-glacial-aged fluvial, lacustrine and aeolian deposits. In places the drift cover can be 10s of metres thick. The sedimentology, thickness, composition, and compaction of the drift cover fundamentally influence much of the biological, hydrological, permafrost, and geomorphic characteristics of the landscape. Understanding the drift cover is thus recognized as being a key component of infrastructure development design and assessment, drift geochemical mineral and ore deposit exploration, and of particular relevance to all manner of ecological studies.This study principally uses seismic shothole drillers' logs (~275,000), collected during auger drilling of shotholes (10-40 m deep) to create cumulative drift isopach (thickness) models and derivative till isopach models. Transparencies of these two isopach models, overlaid onto a digital elevation model, depict areas of both positive constructional relief, and areas where drift has infilled valleys and/or blanketed the underlying topography. Differences and regional trends of drift and till thickness can be linked to compressional and extensional dynamics of glacial entrainment and deposition, and areas where glaciers impounded the regional drainage, into which sedimentation was focused.Further in aid of drift prospecting exploration, this study presents an identification of different till facies. Understanding of till facies is important because different facies are associated with either changes in glacial flow direction, and hence, bedrock source material, or can be used to characterize tills comprised of more locally derived bedrock material such as typically shale-rich basal "blue tills" found in the southeastern and central Mackenzie corridor, compared to overlying "brown tills" which are comprised of more far travelled, englacially transported Canadian Shield derived materials, deposited by deglacial lodgement and meltout processes. Understanding which till is being sampled during surface sediment collection, and hence, which types and locations of bedrock the sediments have been derived from, is critically important to the interpretation of drift geochemical analytical results.