Nunatak

Nunatak [Inuktitut, "lonely peak"], is a MOUNTAIN rising above large ice sheets. Nunataks were first described from Greenland but also occur in Antarctica and Canada, particularly ELLESMERE ISLAND. The term is also used for any nonglaciated area, highland or lowland, which was surrounded by GLACIER ice. Such nunataks may have been biological refugia where plants and animals survived Quaternary GLACIATION and from which they dispersed as the glaciers melted. This controversial "nunatak hypothesis" was developed to explain strange biotic distributions in Canada and Scandinavia.

Quaternary nunataks have been identified in the highlands and leeside lowlands of Baffin Island and Labrador, above or beyond the Laurentide ice limit. Lowlands around Clyde Inlet (Baffin Island) and Iron Strand (Labrador) have undisturbed raised beaches with FOSSILS predating the last glaciation. Mountain nunataks have heavily weathered rock surfaces with former ice limits marked by MORAINES or trimlines, below which the rocks appear freshly ice scoured. Several weathering zones, at different altitudes, indicate that the nunataks survived several glaciations. Similar weathering zones and certain plant distributions suggest that Quaternary nunataks exist around the Gulf of St Lawrence. Counter arguments attack the biological evidence and suggest that cold-based glaciers, known to perform little EROSION, may have protected the weathered surfaces during glaciation.

Author R.J. ROGERSON