Boulder Edge-roundness as an Indicator of Relative Age: a Lochnagar Case Study.
A method is presented for quantifying the degree of edge roundness of large crystalline boulders using a simple instrument. The method utilises the transition due to granular disintegration from sharp to rounded boulder edges, so that the degree of edge roundness is a function of time and can be use...
| Published in: | Scottish Geographical Journal Vol. 121; no. 2; pp. 219 - 237 |
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| Format: | Article |
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Taylor & Francis Ltd
Jun2005
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| Online Access: | View this record in EBSCOhost |
| Summary: | A method is presented for quantifying the degree of edge roundness of large crystalline boulders using a simple instrument. The method utilises the transition due to granular disintegration from sharp to rounded boulder edges, so that the degree of edge roundness is a function of time and can be used as a relative dating tool. Edge roundness can be precisely measured in the field if strict morphological criteria are adhered to when selecting boulders to measure. Roundness can be expressed as a length measurement between fixed points on adjacent facets, as a normalised index, or as a radius of curvature. Boulder edge-roundness was employed to resolve uncertainty over the extent of the ‘Loch Lomond Stadial’ (LLS) glacier in the North-east Corrie of Lochnagar. Small but significant differences in edge roundness between two sets of moraine ridges indicate that the LLS glacier was smaller than that mapped by Sissons & Grant (1972). The moraine they ascribed to the LLS relates to an earlier advance within Late Devensian time. |
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