CGRG Bibliography of Canadian Geomorphology
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Author : Francis, D.; Wolfe, A.; Walker, I.; and Miller, G.
Date : 2000.
Title : A 90,000-year record of fossil chironomid and climate change at Fog Lake, Baffin Island.
Publication : 30th International Arctic Workshop, Program and Abstracts, 2000. Institute of Arctic and Alpine Research, University of Colorado at Boulder
Issue :
Page(s) : 62.
Abstract
To address questions concerning future global climate change, it is necessary to understand natural climate variation over a range of timescales in the past. The Canadian Arctic is a particularly sensitive area, and is critical for our understanding of past climate change at high latitudes. One proxy measure of temperature/climate that remains essentially unexplored in arctic records is the fossil remains of the aquatic insect group Chironomidae (Diptera). Chironomid remains are being examined in a 137-cm core from Fog Lake on the Cumberland Peninsula, Baffin Island. The core was collected as part of the NSF-PALE initiative. Fog Lake probably remained unglaciated during the late Wisconsinan period. The core includes both Holocene sediments (Unit 5, gyttja), and pre-Holocene layers. Although sedimentation may not have been continuous in this lake, and dating of older strata remains problematic, it is believed that Units 1- 4 represent a time period extending from the Holocene back to the penultimate glaciation. Chironomid assemblages show dramatic shifts in species composition throughout the core, corresponding in part to the lithological units. Concentrations of head capsules were extremely high at the base of Unit 3, which is dated at approximately 90,000 yrs BP. In Unit 3, which was probably deposited during the last interglacial (OIS 5), inferred water temperatures are warmer than present. Warm conditions at this time were also suggested by the diatom and pollen data. In Unit 4, a minerogenic laminated silt that probably represents OIS 2-4 during the last glacial maximum, Oliveridia is the dominant taxon, but is rare or absent in other sections of the core. Preliminary results indicate that water temperatures during this interval were around 10°C, although there may have been hiatuses in sediment accumulation during this period. The sediments in this unit may have been deposited during interstadials. Concentrations of head capsules were lowest in this time interval. Some taxa, such as Abiskomyia, are present only in the most recent Holocene intervals. This work represents one of the first stratigraphic studies of chironomid remains in Arctic Canada, and one of few anywhere to examine pre-Holocene assemblages. In addition to the Fog Lake core material, surface samples from a suite of lakes on a north-south transect of the Cumberland Peninsula are being enumerated to provide additional data for chironomid-based temperature inference models.
Bibliography of Canadian Geomorphology