Reconstructing the confluence zone between Laurentide and Cordilleran ice sheets along the Rocky Mountain Foothills, south‐west Alberta

Abstract

Landform mapping near the Athabasca valley was fundamental to determining whether or not the Late Wisconsinan Laurentide and Cordilleran Ice Sheets coalesced. In this paper we examine the detailed landform record using new LiDAR digital elevation and hillshade models of the area of confluence and eventual desuturing of these ice sheets. This work reveals an earlier more extensive Cordilleran advance prior to coalescence with the LIS. When the ice sheets coalesced, the flow pattern is dominated by ice flow along the mountain front, with Cordilleran ice flowing out of major trunk valleys but Laurentide ice flowing into the Foothills up smaller valleys. This flow pattern implies that when the ice sheets coalesced the CIS was already waning, or at least was not at its maximum. Deglaciation was interrupted by several re-advances, likely related to the destabilizing effect of proglacial lakes along the ice margin.

An updated radiocarbon-based ice margin chronology for the last deglaciation of the North American Ice Sheet Complex

“…12 and B1-2) to better align with regional topography and major mapped moraines. Although not shown on our maps, the updated ice margins also align with recent work on the formation of proglacial lakes along the retreating ice margin in this region (Utting et al, 2016a). In Saskatchewan, more substantive changes include an increased region of unglaciated terrain from 18 ka to ~14 ka to better align with previous surficial mapping of the unglaciated terrain and ice marginal features (Klassen, 1991(Klassen, , 1992Klassen, 2002).…”

A late-glacial lake-effect climate regime and abundant tamarack in the Great Lakes Region, North America

“…These conditions suggest increasing atmospheric temperatures and moisture content across the EOL-AP during P2early. However, the incoming westerlies had transitioned from cool Pacific westerlies to cold dry northwesterlies as the north-south corridor between the LIS and CIS widened (Dyke et al, 2003; Atkinson et al, 2016; Utting et al, 2016; Figs. 3B and C and 4B and C).…”

“…On the synoptic scale, atmospheric circulation and the prevailing westerlies upwind of the lakes were likely altered by the relative position of the LIS and Cordilleran Ice Sheet (CIS) and their associated winds (e.g., Rind, 1987; Atkinson et al, 2016; Utting et al, 2016; Figs. 3 and 4).…”

Glacitectonic rafts and their role in the generation of Quaternary subglacial bedforms and deposits

“…These landform-sediment associations record the operation of the northern end of the CAIS (cf. Evans et al, 2008) and its tributaries, the onset zones of the Lac la Biche Ice Stream (Andriashek and Fenton, 1989) that migrated westward into the head of the CAIS during Event 2 of Ó Cofaigh et al (2010) and Norris et al (2018), and the High Plains Ice Stream (HPIS) and its northern tributaries (Evans et al, 2008(Evans et al, , 2014Ó Cofaigh et al, 2010;Atkinson et al, 2014;Utting et al, 2016).…”

“…2). The site is in a pronounced glacitectonic landscape (Fenton et al, 1986;Tsui et al, 1989) within the footprint of the southerly flowing HPIS (Evans et al, 2008(Evans et al, , 2014Ó Cofaigh et al, 2010;Atkinson et al, 2014;Utting et al, 2016). Five main cliff sections contain important information on the processes occurring during the transport, disruption, and accretion of rafts .…”