Microsedimentological evidence of vertical fluctuations in subglacial stress from the northwest sector of the Laurentide Ice Sheet, Northwest Territories, Canada

• Published in: Canadian Journal of Earth Sciences
• Main Authors: Rice, Jessey M., Menzies, John, Paulen, Roger C., McClenaghan, M. Beth
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 2019
• Subjects: General Earth and Planetary Sciences; Northwest Territories; Canada; Pine Point; Ice Sheet
• Online Access: http://dx.doi.org/10.1139/cjes-2018-0201; http://www.nrcresearchpress.com/doi/full-xml/10.1139/cjes-2018-0201; http://www.nrcresearchpress.com/doi/pdf/10.1139/cjes-2018-0201

The past-producing Pine Point lead–zinc mining district, Northwest Territories, Canada, provides a unique opportunity to study the role of glacial dynamics in a thick, continuous till succession that has not been influenced by the underlying bedrock topography. Parts of the Pine Point mining district are covered by >20 m of subglacial Quaternary sediments (till) associated with the former Laurentide Ice Sheet. Till facies exposed in unreclaimed open-pit K-62 have been classified into four separate units. Micro- and macrosedimentological analyses were undertaken to identify the change in subglacial stress during sediment deposition and across till unit boundaries. An analysis of high- and low-angle microshears (lineations) in thin sections produced from these till units indicate that there is a noticeable decrease in the abundance of low-angle shear features immediately below till unit boundaries. The deformation of low-angle shears in the underlying tills was likely caused by remobilization of the overlying till unit. This remobilization is consistent with aggradation-constant entrainment decay mechanisms for subglacial till emplacement and accretion and subglacial dispersion models.