VARIATIONS OF OXYGEN ISOTOPIC COMPOSITION AND DISTRIBUTION OF CONTINENTAL ICE IN THE LAST ICE AGE. (II) MASSIVE GROUND ICE BODY IN ARCTIC CANADA

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Massive ground ice bodies are seen in the Canadian Arctic. The origins and formation processes of the ice bodies remain in need of research. So, I am studying a massive ground ice body in Mackenzie Delta, N. W. T., Canada, on the basis of a hypothesis that it is a relict ice body of the Laurentide ice sheet. If so, a massive ground ice body should provide important information about oxygen isotopic composition of the Laurentide ice sheet. Dating of the ice body must supply an important key in clarifying its origin and formation processes. Radiocarbon dates of the sediments found in the core samples obtained throughout the massive ice body were first determined by accelerator mass spectrometry. The sediments taken from the core at depths around the midpoint and bottom of the ice body were dated at 14270 and 17070 years B. P., respectively. The dates of reworked till overlying the ice body and of twigs found in the till layer were >23000 and <10000 years B. P., respectively. Therefore the massive ice is considered to have been formed before 10000 years B. P. and, accordingly, to be not segregated ice origin but buried ice origin. On the other hand, oxygen isotopic composition and pollen content show a decreasing trend from the bottom to top of the ice body. Correlation between these trends and the determined dates indicates that the massive ice body was not formed in Mackenzie Delta but had moved from south of the delta before 10000 years B. P.; namely, it is a relict ice body of the Laurentide ice sheet.
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Kato Kikuo
Water Research Institute Nagoya University

VARIATIONS OF OXYGEN ISOTOPIC COMPOSITION AND DISTRIBUTION OF CONTINENTAL ICE IN THE LAST ICE AGE. (II) MASSIVE GROUND ICE BODY IN ARCTIC CANADA

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