Weathering Pits as Indicators of the Relative Age of Granite Surfaces in the Cairngorm Mountains, Scotland |
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| Authors: | Adrian Malcom Hall William Morton Phillips |
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| Institution: | School of GeoSciences, University of Edinburgh, Edinburgh, UK;, Idaho Geological Survey, University of Idaho, Moscow, USA |
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| Abstract: | Weathering pits 1–140 cm deep occur on granite surfaces in the Cairngorms associated with a range of landforms, including tors, glacially exposed slabs, large erratics and blockfields. Pit depth is positively correlated with cosmogenic exposure age, and both measures show consistent relationships on individual rock landforms. Rates of pit deepening are non‐linear and a best fit is provided by the sigmoidal function D = b1 + exp(b2+b3/t). The deepest pits occur on unmodified tor summits, where 10Be exposure ages indicate that surfaces have been exposed to weathering for a minimum of 52–297 ka. Glacially exposed surfaces with pits 10–46 cm deep have given 10Be exposure durations of 21–79 ka, indicating exposure by glacial erosion before the last glacial cycle. The combination of cosmogenic exposure ages with weathering pit depths greatly extends the area over which inferences can be made regarding the ages of granite surfaces in the Cairngorms. Well‐developed weathering pits on glacially exposed surfaces in other granite areas are potential indicators of glacial erosion before the Last Glacial Maximum. |
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| Keywords: | weathering pit cosmogenic exposure age granite landform |
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