The Holocene history of the Columbia Icefield, Canada.

The Columbia Icefield is the largest icefield in the Canadian Rockies and feeds eight major glaciers that drain to three different oceans. Previous glacier studies have focused on Athabasca and Saskatchewan Glaciers, primarily due to their easy access. This paper reviews evidence of the Holocene history from all eight glaciers. Maximum Holocene glacier extent was during the Little Ice Age (LIA) with dating based mainly on minimum tree-ring estimates from trees growing on the moraines or from trees scarred, tilted or killed by the glaciers. The LIA maximum advance was during the 19th century at Athabasca (1843/4), Dome (1846), Saskatchewan (1862) and Castleguard (<1858) Glaciers but during the 18th century at Manitoba (1740), Columbia (<1739), Kitchener (<1713) and Stutfield (1758). Advances in 1714 (Athabasca) and 1740 (Saskatchewan) were of almost equal extent to the 19th century maxima. Early LIA advances are identified from a buried in-situ stump at Stutfield (>1271) and detrital wood from lateral moraines at Columbia (ca. 0.8-0.7ka). Two overridden stumps at Columbia Glacier indicate a previously unidentified advance ca 1500 A.D. These four phases of LIA coincide with major reductions in summer temperatures reconstructed at the Icefield. There are also undated (pre-1600, possibly pre LIA) moraines at Kitchener Glacier. Less extensive Neoglacial glacier events are documented by an in-situ forest bed buried by the Saskatchewan Glacier (ca 2.90–3.4 ka., equivalent to the "Peyto advance") and stumps buried by till ca. 4.2ka at Boundary Glacier. Detrital wood recovered from till at Columbia Glacier indicates at least one glacier advance ca 2.0-2.2ka. Till exposed between the Bridge River and Mazama tephras at Stutfield Glacier includes detrital wood dating 2.22–2.70 ka that possibly indicates a glacier advance immediately prior to the Bridge River tephra. Regional paleoenvironmental data indicate warmer conditions and higher treelines in the early Holocene. Detrital wood washed out of Dome and Athabasca Glaciers indicates trees were present in these valleys ca 6, 7 and 9ka upvalley of present glacier snouts. Evidence from Castleguard cave indicates upstream entrances below the present Icefield were probably ice free ca 9.5ka indicating the icefield was much reduced in extent at that time. The detrital wood may represent wood killed and reworked by limited glacier advances from the Icefield, far upstream of present glacier fronts, at these times. • Reviews and updates evidence of Holocene glacier history for eight glaciers draining from the Columbia Icefield. • Results based on field mapping, tree-ring and radiocarbon dating. • Identifies four Little Ice Age phases including new evidence for a possible advance ca 1500 AD • Confirms Neoglacial advances at ca 3000 and 4200 ka plus advances before (ca. 2.0–2.2ka) and after ca 2.5 ka. • Discusses detrital evidence of possible limited glacier events ca. 6, 7 and 9ka. [ABSTRACT FROM AUTHOR]