Paleoglaciological dynamics in northern Manitoba and the subglacial bed mosaic

• Main Author: Trommelen, Michelle Suzanne
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: University of Waterloo 2013
• Subjects: Quaternary; Glacial; Earth Sciences; Ice Sheet
• Online Access: http://hdl.handle.net/10012/7645

During the last glacial maximum (LGM), some 20 ka ago, northern Manitoba was situated beneath 3 to 4.5 km of ice, on the outer fringe of a major ice spreading center of the Laurentide Ice Sheet. The region has also been affected by major paleoglaciological changes linked to multiple source areas, migration of ice centres, and ice-sheet thickening/thinning over multiple glacial cycles. The net effect of this evolution is a very complex geological record, which has major implications for ice-sheet reconstructions and drift prospecting. Theory-based hypothesis for the region suggest initial advance-phase deposition was followed by either net-erosive or cold-based conditions for much of the glacial cycle. In contrast, observation-based reconstructions of ice-sheet behaviour consider the glacial landscape to have been predominately formed by near-complete overprinting during warm-based deglaciation. Some complexity has been recognized in sediment-landform records, but new insights into glacial dynamics and sediment-landscape evolution are needed. Systematic mapping (remote-sensing) and fieldwork (ice-flow indicators, till composition, ground truthing) in northeastern Manitoba has led to the recognition of spatio-temporal variability in landscape (streamlined-landform event-flowsets) and landform (micro and meso-scale ice-flow indicator records) and till composition inheritance. In particular, analysis of the spatio-temporal characteristics of the subglacial landscape led to the recognition of disjoint zones with internally-consistent assembly histories – termed glacial terrain zones (GTZ). These GTZ were then classified as (1) relict-glacial, (2) palimpsest, or (3) deglacial in nature. Generally, (1) is interpreted as pre-LGM, (2) may include pre-LGM terrain but also LGM to early deglaciation (ice margin still far from study area; ice sheet thinning phase) and (3) was formed during the final ice retreat phase. The resultant surface till composition within relict and palimpsest GTZs is a spatial mosaic interpreted to ...