Flow‐pattern evolution of the Laurentide and Cordilleran ice sheets across west‐central Alberta, Canada: implications for ice sheet growth, retreat and dynamics during the last glacial cycle

Abstract

This paper presents a reconstruction of the geometry, dynamics and flow pattern of the Laurentide and Cordilleran ice sheets along the Albertan portion of the eastern Canadian Rocky Mountains during the last glaciation. Sediment–landform associations relating to the evolution of these ice sheets document their initial convergence and mutual deflection across west‐central Alberta. The continued advance of Laurentide ice locally displaced Cordilleran ice westward into the Front Ranges, and deflected trunk ice emerging from the Athabasca River valley south‐eastwards along the Foothills. These convergent flow patterns remained major features in the regional geometry of both ice sheets throughout the Last Glacial Maximum. The onset of deglaciation was characterized by the northward retreat of the Laurentide Ice Sheet, which progressively unblocked valleys along the mountain front. The configuration of buttress removal initiated the Lateglacial expansion and sequential drawdown of the eastern Cordilleran Ice Sheet along fast‐flowing outlet glaciers. Subsequent regional retreat of Laurentide and Cordilleran ice was associated with the development of large proglacial lakes which amplified deglaciation by destabilizing the margins of both ice sheets, triggering extensive readvances due to periodic changes in water level associated with the opening and closing of outlets by ice margin fluctuations.

Glacial geomorphology of the Neutral Hills Uplands, southeast Alberta, Canada: The process-form imprints of dynamic ice streams and surging ice lobes

“…These reconstructions demonstrate that during full glacial and deglacial conditions, this sector of the ice sheet was subject to ice streaming and the intermittent operation of surging lobes, which promoted dramatic switches in ice flow directions (Clayton et al, 1985;Evans et al, , 2008Ó Cofaigh et al, 2010;Margold et al, 2015;Atkinson et al, 2016; Fig. 1).…”

Glacial geomorphological mapping: A review of approaches and frameworks for best practice

“…Nonetheless, cartographic reduction is often still required to manage the volume of information, resulting in the grouping of similarly-orientated bedforms into flow-sets (occasionally termed fans or swarms) (e.g. Jansson et al, 2002Jansson et al, , 2003De Angelis and Kleman, 2007;Greenwood and Clark, 2009a, b;Hughes et al, 2014;Atkinson et al, 2016).…”

Using10Be dating to determine when the Cordilleran Ice Sheet stopped flowing over the Canadian Rocky Mountains

“…The interaction between the Cordilleran and Laurentide ice sheets east of the Rocky Mountains at the LGM has been debated for many decades, with some researchers arguing for the coalescence of the two ice sheets on the westernmost Interior Plains (e.g., Mathews, 1978;Dyke and Prest, 1987;Stumpf et al, 2000;Dyke et al, 2003;Dyke, 2004;Bednarski and Smith, 2007), while others argue that the CIS did not extend over the Rocky Mountains at the local LGM (lLGM) (e.g., Bobrowsky and Rutter, 1992;Catto et al, 1996). Recently, empirical evidence supporting the coalescence of the two ice sheets has grown (Atkinson et al, 2016;Hickin et al, 2016;Hartman et al, 2018), and it is now generally accepted that they coalesced at the lLGM (Fig. 1).…”