Plateau icefield landsystems

Plateaux are topographical features typical of many mountain regions and are perhaps best developed in passive margin settings, that have experienced significant periods of tectonic stability. Such conditions allow the preservation of palaeo-landsurfaces, which may have subsequently been uplifted and/or incised (Goddard, 1989). Good examples of such landscapes are found on the west and east sides of the North Atlantic, for example in Norway, the British Isles, USA, Greenland and in the island archipelago of the Canadian Arctic. Areas of Iceland also contain plateaux (Brown and Ward, 1996), where the plateaux (stapis or tuyas) are often the products of geologically recent subglacial volcanic eruptions (van Bemmelen and Rutten, 1955; Jones 1969). This chapter compiles a diagnostic assemblage of landforms and criteria that can be used to identify or infer the existence of former plateau icefields. Ice masses reconstructed from glacial geology are often used to reconstruct regional palaeo-climate, but evidence of glacierization on plateaux is often subtle and/or missing. It is therefore essential that plateau-style glaciation is recognized and the glaciers are reconstructed with realistic hypsometry (e.g. Furbish and Andrews, 1984; Benn and Lehmkuhl, 2000) as this can have a major impact on equilibrium line altitudes (ELAs) and on the climate thus inferred. A lack of appreciation of valley and associated plateau glaciers has often led to the misinterpretation of the geometry of ice coverage and thus the reconstruction of erroneous palaeo-ELAs.