The sea-level record preserved in ancient shorelines forms a basis for
studies of tectonic uplift, glacial loading, and the changing volume
of the oceans. The existing record is derived largely from depositiona
l features such as beach ridges and coral reefs, which contain materia
l suitable for radiometric dating. Erosional shorelines have proved mo
re difficult to date. Direct age estimates for shore platforms can now
be obtained with exposure-dating techniques based on cosmic-ray-produ
ced isotopes. Here we report measurements of cosmogenic Cl-36 on the M
ain Rock Platform in western Scotland that indicate its formation in a
postglacial event spanning less than a few thousand years. Together w
ith isostatic modeling, the Cl-36 results suggest cutting during the Y
ounger Dryas (in Britain, the ''Lateglacial'' or ''Loch Lomond'') Stad
ial, when stable sea Level and severe climatic conditions combined to
enhance bedrock erosion.