Holocene (Neoglacial) moraine and proglacial lake chronology, Barnes Ice Cap, Canada |
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| Authors: | JOHN T ANDREWS D MARTIN BARNETT |
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| Institution: | Institute of Arctic and Alpine Research and Department of Geological Sciences, University of Colorado, Boulder, Colorado, 80309, U.S.A.;Environmental Assessment Division, Department of Indian and Northern Affairs, Ottawa, Ontario, Canada;2nd October, 1978. |
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| Abstract: | Lichen diameters and radiocarbon dates from the western and southern margins of the Barnes Ice Cap yield a growth curve similar to that from southeastern Baffin Island. As a consequence, the moraine chronology of the northern and western Barnes Ice Cap needs revision, as does the chronology of the large proglacial lakes that existed north of the present Barnes Ice Cap. The revised chronology indicates that moraines were formed along the western margin of the Barnes Ice Cap during the following intervals: (1) less than 100 years ago; (2) 400–500 B.P.; (3) ca. 750 B.P.; (4) ca. 1000 B.P.; (5) ca. 1600 B.P.; (6) ca. 2100 B.P.; and (7) 2800 to 3100 B.P. As the western margin of the Barnes Ice Cap retreated, punctuated by stillstands and readvances, the northern margin of the Barnes Ice Cap lay athwart a series of westerly draining valleys, and a complex of proglacial lakes were dammed between the ice margin and the height of land. This sequence is traced by means of well-developed shorelines, lacustrine deltas, and spillways; specific lake levels are dated by lichenometry.
The Barnes Ice Cap moraine sequence is more complex than other Neoglacial records fringing mountain glaciers in Colorado, Alaska and Lappland. However, the chronology for the western Barnes Ice Cap closely resembles independent moraine chronology of mountain glaciers in Cumberland Peninsula, Baffin Island, and thus indicates that the difference between the Baffin Island climatic record and the general Neoglacial/Holocene climatic record (Denton & Karlén, Quaternary Research 7 , 1977) is real. Comparison of specific data from Swedish Lappland and Baffin Island shows substantial agreement. Although Neoglacial records may be globally synchronous, the case for a 2500 year periodicity of glacial fluctuations is not proven: a 300 to 600 year return interval is suggested for the period between 0 and 3000 B.P. |
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