ABSTRACT: Late Holocene glacial, vegetational, and climatic history of Pangnirtung and Kingnait fiord areas, Baffin Island, N.W.T., Canada

CGRG Bibliography of Canadian Geomorphology
Search Results

Author :

Date :

Title :

Publication :

Issue :

Page(s) :

Abstract

In this area, glacier moraine records and lacustrine and peaty sediment sections document complex responses to late Holocene climatic changes. A Neoglacial chronology is derived from detailed lichenometric studies on over 85 moraines fronting 27 glaciers in three separate study areas on southern Cumberland Peninsula. Six radiocarbon assays date the growth curve for Rhizocarpon geographicum sensu lato on Baffin Island. Major periods of moraine stabilization (still-stand or retreat) occurred on southern Cumberland Peninsula < 100, 200-400 and 500-650 yrs BF (Cumberland Advances), 900-1150 yrs BP (Pangnirtung Advance), 1900-2000 and 2200-2400 yrs BP (Kingnait Advances), and 2900-3100 yrs BP (Snow Creek Advance). Broad synchrony for moraine stabilization in three regions of Baffin Island and one area in northern Labrador are now recognized, although the moraine evidence for the Dorest Advance (1500-1600 yrs BP) was not observed on southern Cumberland Peninsula. The Neoglacial moraine chronology for Baffin Island resembles glacier records from Swedish Lappland and Alaska-Yukon, although the Baffin Island moraines show many more events. Silty sediments from Shadow Lake, below a small cirque glacier, are not simply a continuous record of glacier mass balance changes because of numerous interbedded sandy layers. By contrast, the coarse-grained sediments from Shadow Lake suggest debris avalanches culminated just before 3200 yrs BP and about 2500, 2250, 1950, 1100, and 900 yrs BP. This record is in-phase with periods of moraine stabilization on southern Cumberland Peninsula except for the Little Ice Age. During the last 700 yrs, coarse debris did not reach Shadow Lake, although higher organic matter percentages at about 400 and 800 yrs BP in the silty sediments may suggest warming following glacier advances. Studies of modern pollen deposition in surface lacustrine sediments, moss polsters, and Tauber traps allow interpretation of past palynological records in terms of qualitative vegetational changes. Meteorological records and contemporary local and regional pollen were also used to develop transfer functions and to estimate numerical paleoclimatic variations. Pollen diagrams from the Windy Lake peat are dominated by Gramineae throughout its 3700-yr record except for a short-lived Salix peak about 2400 yrs BP. Three sand layers and the cessation of peat growth about 2050-1950, 1700-1450, and 600-0 yrs BP probably indicate greater cold, but transfer functions suggest that the sand layers may not reflect extremely dry conditions. Exotic tree pollen numbers mirror peaks of total pollen concentration and may indicate slower sediment accumulation, increased vegetational productivity, and/or more intense southerly airflow. Peaks of exotic Picea and Pinus pollen from the Windy Lake peat do not strongly correlate with dates on moraine stabilization. However, resolution of radiocarbon and lichenometric chronologies are here at the limit of their capabilities. The dominant pollen taxa from Iglutalik Lake during the last 4000 yrs fluctuate synchronously and exhibit six peaks at 3950, 3550-3450, 2650, 1800, 1200-1100, and 550 yrs Bp, roughly correlating with periods of glacier retreat. This may have been due to warmer climatic effects. Exotic Alnus pollen decreased as exotic Picea and Pinus increased between 4000 and 3300 yrs Bp at Iglutalik Lake due to warm, southerly, summer winds passing over advancing forests in central Labrador. The transfer function paleoclimatic estimates from Iglutalik and Windy Lake sites show parallels in July temperatures, but contrasts in summer precipitation, possibly due to presence or absence of maritime (sea-ice) effects.

Bibliography of Canadian Geomorphology