The Donegal ice dome,northwest Ireland: dimensions and chronology |
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| Authors: | Colin K Ballantyne Danny McCarroll John O Stone |
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| Institution: | 1. School of Geography and Geosciences, University of St Andrews, Fife, Scotland, UK;2. Department of Geography, University of Wales Swansea, Swansea, Wales, UK;3. Department of Earth and Space Sciences and Quaternary Research Center, University of Washington, Seattle, Washington, USA |
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| Abstract: | Geomorphological evidence indicates that Donegal was formerly occupied by an ice dome that extended offshore to the west, northwest and north and was confluent with adjacent ice masses to the east and south. Erosive warm‐based ice over‐rode almost all the highest mountains, implying an ice‐divide altitude greater than 700 m. Only six peripheral summits escaped glacial modification, implying either that they remained above the ice surface as nunataks or supported a thin cover of protective cold‐based ice. Gibbsite, a pre‐last glacial weathering product, is preferentially represented on summits that escaped glacial modification. Cosmogenic 10Be exposure ages of 18.6 ± 1.4 to 15.9 ± 1.0 k yr for coastal sites confirm that Donegal ice extended offshore at the last glacial maximum. Reconstruction of the form of the Donegal ice dome suggests a former minimum ice thickness of ～500 m close to the present coastline in the west and northwest, and ～400 m near the coast of the Inishowen Peninsula in the north, with the ice extending at least 20 km across the adjacent shelf to the west and northwest. Copyright © 2007 John Wiley & Sons, Ltd. |
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| Keywords: | palaeonunataks cosmogenic isotope exposure dating clay‐fraction mineralogy ice‐sheet reconstruction |
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