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The Nunatak Theory Reconsidered

Eilif Dahl
Ecological Bulletins
No. 38, Research in Arctic Life and Earth Sciences: Present Knowledge and Future Perspectives. Proceedings of a Symposium Held 4-6 September, 1985, at Abisko, Sweden (1987), pp. 77-94
Published by: Oikos Editorial Office
Stable URL: http://www.jstor.org/stable/20112974
Page Count: 18
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The Nunatak Theory Reconsidered
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Abstract

The nunatak theory proposes that unglaciated areas existed along the shores of the North Atlantic ocean where plants and animals survived the last or previous glacial ages. This theory is examined in light of recent research. Reconstructions of summer temperature conditions 18,000 years ago suggest that the lowland flora of Scandinavia could not survive in icefree refuges but immigrated from the south or east when the ice melted. However, numerous species of the alpine flora could not survive in the lowlands south and east of the north European ice sheet 18,000 years ago and must have survived in ice-free refugia. This is confirmed by an analysis of the phytogeographic affinities of the lowland and the alpine floras. A relatively high amount of endemism, presence of numerous amphiatlantic species lacking in the Alps and similarity between the alpine-subalpine floras of Iceland, the British Isles and Scandinavia indicate that these floras survived in refuges since early Pleistocene times. Recent geological evidence suggest that a land area once connected Scandinavia, Scotland and Iceland up to Late Pliocene -- Early Pleistocene. With present topography several areas around the North Atlantic could not be covered by an inland ice because of the plasticity of ice. New dating methods (amino acid analysis, thermoluminescence) show that some areas in Spitsbergen have remained ice-free during most of the Pleistocene. Presence of gibbsite and other clay minerals suggest that the mountain top detritus is a remnant of the Tertiary weathering crust which has survived the Pleistocene glacial ages.

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