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Late Quaternary sediment records from the northernmost lake archive of the Yukon (Herschel Island, Western Canadian Arctic)

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Citation:
Lenz, J. , Fritz, M. , Lantuit, H. , Wetterich, S. , Schirrmeister, L. , Pollard, W. H. , Frenzel, P. and Lorenz, S. (2010): Late Quaternary sediment records from the northernmost lake archive of the Yukon (Herschel Island, Western Canadian Arctic) , ArcticNet Annual Scientific Meeting (ASM2010), 14-17 December, Ottawa, Canada. .
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Abstract:

In spring 2009, a 730 cm sediment core was recovered from the largest lake on Herschel Island (Yukon Territory, Canada). This is one of the first continuous paleo-records in the Western Canadian Arctic and the northernmost archive derived from lake sediments in the Yukon.Located 70 km east of the Yukon-Alaska border in the Southern Beaufort Sea and with a maximum elevation about 180 m, Herschel Island is presumably a terminal moraine representing the westernmost extension of the Wisconsin glaciation. Characterizing the paleoenvironment and determining the age of the maximum glacial extent are important outcomes for Quaternary research and for the settlement history of Canada. A multi-proxy approach was applied to analyse the lake sediments and pore water. A combination of biogeochemical parameters (TC, TOC, TN), grain size analysis, magnetic susceptibility, x-ray fluorescence and stable isotope determination (δ13C) as well as the hydrochemistry of pore water (pH and electrical conductivity) were used to yield information about the late Quaternary limnology of Lake Herschel. Age determinations by radiocarbon dating allowed to develop an age-depth model of the sediment core. Our results from various analyses of the sediment core point towards four distinguished stratigraphic and lithologic units. A sharp contact, probably related to mass movements in the vicinity of the lake, divides the uppermost two units. The most prominent feature of the core, however, relates to a drastic change in sedimentology indicating the transition from late Holocene to Pleistocene between the lowermost two units at a depth of 700 cm. Electrical conductivity was observed to increase steadily with depth, providing an indication about the water balance throughout the Holocene. The brackish water conditions in the lake seemed to have interestingly enabled liveable conditions for both marine and freshwater organisms at the same time (ostracodes, foraminifera, molluscs). The results from this core refl ect the catchment sedimentology but provide a highly detailed and unique record of the paleoenvironment of the coastal western Arctic to be compared with similar records from both the neighbouring Ocean and the more southern lake sediment records in the Yukon.

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