A glacial readvance during retreat of the Cordilleran Ice Sheet, British Columbia central coast

Abstract

Descriptions of the Cordilleran Ice Sheet retreat after the last glacial maximum have included short-lived readvances occurring during the Older and Younger Dryas stadial periods and into the Holocene, but identification of these events has been largely limited to southwest and central British Columbia and northwest Washington State. We present evidence of a late Pleistocene readvance of Cordilleran ice occurring on the central coast of British Columbia on Calvert Island, between northern Vancouver Island and Haida Gwaii. Evidence is provided by sedimentological and paleoecological information contained in a sedimentary sequence combined with geomorphic mapping of glacial features in the region. Results indicate that a cold climate existed between 15.1 and 14.3 cal ka BP and that ice advanced to, and then retreated from, the western edge of the island between 14.2 and 13.8 cal ka BP. These data provide the first evidence of a major fluctuation in the retreating ice sheet margin in this region and suggest that a cold climate was a major factor in ice readvance. These data contribute to the understanding of past temperature, ice loading and crustal response, the nature of ice margin retreat, and the paleoenvironment of an understudied area of the Pacific Northwest.

Retreat of the Western Cordilleran Ice Sheet Margin During the Last Deglaciation

“…Buxton, but it thinned markedly. Hecate Island was exposed at 14.2 ± 0.5 ka, likely during retreat following a readvance of the ice sheet given the similarity between our exposure ages and radiocarbon ages for a readvance on Calvert Island (Eamer et al, 2017). At a similar time, two other sites were exposed by ice thinning into fjords below: 14.5 ± 0.7 ka for King Island and 13.8 ± 0.1 ka for Rivers Inlet (Figures 2 and 3 Table S1).…”

“…Bedrock in the area is composed of diorite, quartz diorite, granite, granodiorite, and tonalite (Roddick, 1996); Quaternary glacial landform and sedimentary deposits are relatively uncommon. Moraines are generally aligned east-west or northeast-southwest ( Figure 2) and in places westward, tracking the receding margin of the Cordilleran Ice Sheet (Eamer et al, 2017(Eamer et al, , 2018Neudorf et al, 2015). Figure 2.…”

Late Quaternary landscape evolution in a region of stable postglacial relative sea levels, British Columbia central coast, Canada

“…; Eamer et al . ). This was influenced by climate through the end of the Late Pleistocene, where a number of established cold‐climate periods occurred as anomalies to the general warming trend, such as the Older Dryas ( c. 14 cal.…”

“…ka BP (Eamer et al . ). This re‐advance occurred at Foggy Cove, an important part of the study area for the research described in this paper.…”

“…The stratigraphy, palaeoecology and geochronology was documented in Eamer et al . (), and results will be discussed below. Most other work on terrestrial ice cover in central BC has focused on the Coast Mountains to the east (Fig.…”