Department of geography, Université de Montréal
520, Chemin de la Côte Ste-Catherine
Université de Montréal
514.343.6111 extension 33546
Paleoglaciology of Bylot Island at the Pliocene-Pleistocene Transition
The analysis of ground-ice characteristics can give numerous clues about the geomorphologic processes and the thermal conditions at the time when permafrost developed (Pollard, 1990). Massive underground ice therefore shows a great potential as a natural archive of the earth’s past climate. As a consequence of degrading permafrost, active-layer detachments from the underlying frozen ground expose extensive icy bodies preserved in the permafrost. My project focuses on these massive icy bodies exposed on a plateau located at the southwest end of Bylot Island, in the Canadian High Arctic. This ice was first interpreted as an old relict of glacier ice buried under glacio-fluvial sediments (Fortier, 2009). Through the investigation of the topographic position in the valley, the geomorphologic context, the depositional settings and ages of the overlying deposits, these bodies of massive ice are associated to different episodes of Pleistocene glaciations (early Pleistocene to late Pleistocene/early Holocene). At the oldest site, previous studies based upon the paleomagnetism of the overlying deposits and the amino acid ratios of the shell fragments sampled from the till have associated this buried glacier ice to an early Pleistocene glaciation (Klassen, 1993; Fortier et al., 2009). This glacial event was preceded by a much warmer period that allowed the establishment of a sub-arctic forest on Bylot Island at the very end of the Pliocene (Piraux, 2005; Fortier et al., 2009). As a result, buried glacier ice found on Bylot Island represents a potential source of proxy information on past climates and geomorphologic processes of the abrupt and major climate shift related to the Plio-Pleistocene transition. This project research focuses on reconstitutions of climatic and environmental conditions on Bylot Island based upon Pleistocene–aged permafrost ground-ice. This project has three specific objectives: 1) to characterize the cryofacies and chemico-physical characteristics of the buried glacier ice found on Bylot Island and modern glacier ice; 2) to reconstruct climatic and environmental history of Bylot Island at different moments of the Pleistocene (Plio-Pleistocene transition to Late Pleistocene) 3) to compare climatic reconstruction based on our results with existing regional paleoclimatic models. In order to characterize buried glacier ice at the study site, analysis of crystallographic and cryostratigraphic characteristic of the ice and the enclosing sediments will be conducted. A portable core-drill was used to obtain samples of relict glacier ice. The age of the ice will be determined by paleomagnetism dating of fine sediments sampled from surficial deposits (in collaboration with Guillaume St-Onge, UQAR) and its relative stratigraphic position above the «fossil forest» sequence. Based on the analysis of the sediment particle size, the stratigraphic context of the study site will allow determining the past sedimentary depositional environment that resulted to the burial of glacier ice. As for estimating past climates of Bylot Island, temperature at time of ice formation will be inferred by the stable isotopic composition (d18O) of the air trapped in the ice. Our results will help to quantify the major and abrupt climatic shift that occurred on Bylot Island at the Plio-Pleistocene boundary and the following Pleistocene glacial cycles. The long-term preservation of massive ground-ice and permafrost through the late Quaternary interglacials may suggests the occurrence of negative feedbacks mechanisms that made permafrost resilient to climate changes. Furthermore, little is known about massive underground ice of glacial origin so this study will help to characterize cryofacies and to determine the conditions of burial of glacier ice, and then. Massive ground ice characterization will be required for future northern infrastructure (e.g. Mary River Iron Mine). Indeed, improving knowledge of current permafrost conditions is now critical for northern infrastructure and community developments. References Fortier, F., Godin, E., Kanevskiy, M.Z. et Allard, M. (2009), Middle Pleistocene (?) buried glacial ice on Bylot Island, Canadian Arctic Archipelago. EOS Transactions of the American Geophysical Union, 90 (52): Fall Meeting Supplement, Abstract C41A-0438 Klassen, R.A. (1993). Quaternary Geology and Glacial History of Bylot Island, Northwest Territories. Geological Survey of Canada Memoir 429, Ottawa, Department of Energy, Mines and Resources Canada. Piraux, O. (2005), Contexte paléogéographique de la forêt fossile de l’île Bylot, Arctique Canadien, 132 pp, Université Laval, Québec. Pollard, W.H. (1990), The nature and origin of ground ice in the Herschel Island area, Yukon Territory. Communication présentée à la 5e Conférence canadienne sur le pergélisol, Québec,, no 54 : 23-30
Lacelle, D., Fisher, D.A., Coulombe, S., Fortier, D., Frappier, R., 2018. Buried remnants of the Laurentide Ice Sheet and connections to its surface elevation. Scientific Reports, 8: 13286. DOI: 10.1038/s41598-018-31166-2.
Godin, E., Fortier, D., Coulombe, S., 2014. Effects of thermo-erosion gullying on hydrologic flow networks, discharge and soil loss. Environmental Research Letters, 9(10): 105010. DOI: 10.1088/1748-9326/9/10/105010.