Mid-Holocene glacier expansion between 7500 and 4000 cal. yr BP in the British Columbia Coast Mountains, Canada

Abstract

The mid-Holocene behaviour of five glaciers in the British Columbia Coast Mountains was reconstructed from radiocarbon ages and stratigraphic analysis. Subfossil wood evidence at Canoe, Fyles, Jacobsen, Tchaikazan and Icemaker glaciers suggests these glaciers were expanding into standing forests prior to 6630, 4900 and 4200 cal. yr BP. Stratigraphically constrained woody detritus at Fyles Glacier records the progradational history of a Gilbert-type delta forming in response to glacial expansion between 7020 and 5470 cal. yr BP. This research provides the first evidence for mid-Holocene glacial expansion in the central and northern British Columbia Coast Mountains. Proxy records describing mid-Holocene climates in the British Columbia Coast Mountains indicate a trend towards slightly cooler and possibly wetter conditions than present. Glacial expansion occurring between 7500 and 4000 cal. yr BP has regional correlatives, suggesting coherent broad-scale climate forcing mechanisms influenced glacial mass balance at this time.

Holocene glacier fluctuations

“…The 8 ka advance corresponds to the 8.2 ka event and is consistent with chironomid records from western Canada (Chase et al, 2008;Bunbury and Gajewski, 2009). An update of glacial histories include the papers by Osborn et al (2012), Hoffman and Smith (2013), Clague et al (2010), Coulthard et al (2013), Harvey et al (2012), Koch and Clague (2011), and Koehler and Smith (2011). These studies have recognized an additional period of ice expansion in the Mount Waddington area at 5.8 ka, consistent with other proxy records from palynology, from a marine core along the coast (Galloway et al, 2011) and interior records from lakes (Gavin et al, 2011) that all show decreased summer temperatures.…”

Holocene glacier history of Frank Mackie Glacier, northern British Columbia Coast Mountains

“…A regional exception is the developing understanding of Holocene glacier behaviour within the Bowser River watershed and adjacent Cambria Icefield area in northwestern B.C. Following on the pioneering work of Clague and Mathewes (1992) and Mathews and Clague (1993) at Tide Lake and Berendon Glacier, a number of researchers have described multiple advance and retreat intervals from the mid-Holocene through to the LIA in this region (Jackson et al 2008;Harvey et al 2012;Johnson and Smith 2012;Osborn et al 2012; Hoffman and Smith 2013).…”

Late Holocene Glacier fluctuations in southernmost Patagonia.

“…Rapid retreat of glaciers during the twentieth century has exposed many sites where the stratigraphy of lateral moraines can be studied (Osbom and Karlstrom, 1988;Osbom et al, 2007;Harvey et al, 2012). Some lateral moraines comprise multiple tills and may contain sub fossil wood and tephras that can be studied to establish a chronology of glacier activity (Clague, 1986(Clague, , 1987Ryder and Thomson, 1986;Osbom and Karlstrom, 1989;Desloges and Ryder, 1990;Osbom et al, 2001;Reyes and Clague, 2004;Harvey et al, 2012).…”

“…Some lateral moraines comprise multiple tills and may contain sub fossil wood and tephras that can be studied to establish a chronology of glacier activity (Clague, 1986(Clague, , 1987Ryder and Thomson, 1986;Osbom and Karlstrom, 1989;Desloges and Ryder, 1990;Osbom et al, 2001;Reyes and Clague, 2004;Harvey et al, 2012).…”

“…Stratigraphic sections may also contain unconformities produced by erosion (Clague, 1986). Nevertheless, woody debris, stumps and stems in growth position, paleosols and tephras in lateral moraines yield valuable information on past glacier activity (Ryder and Thomson, 1986;Osbom and Karlstrom, 1988;Reyes and Clague, 2004;Harvey et al, 2012). These types of information have been widely used to develop chronologies of glacier activity in northwestern North America, but have not yet been widely applied in southern Patagonia.…”