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British Geological Survey, Keyworth, Nottingham, NG12 5GG, UK
A macroscale model is attempted to accommodate offshore observations indicative of former sea-levels in the Irish and Celtic seas. The indications considered here are those that appear to post-date 12 ka BP. Raised beaches at about present sea-level, and formed in the Last Interglacial, are found about these seas. This shows that controls to produce the later sea-level changes have acted to return to about their conditions in the Last Interglacial, and that later permanent tectonic displacements have not been significant. A simple, geometrically based model is developed of the interaction of: glacio-eustasy, from graphs based on coral-reef studies; glacio-isostatic depression with an annular forebulge of equal volume, both contracting through the interval considered; and hydro-isostasy, as an enhancement of the other effects by up to 20%. The best fit of the empirical submarine data suggests that from 12 to 9 ka BP relative sea-levels varied from 80 m above, and 160 m below present mean sea-level in the two seas. The resultant sea-level graphs for points from Scotland to Ushant compare with published graphs from eastern North America and northern Europe. Derived maps of palaeocoasts show land-bridges from Britain to Ireland and later to the Isle of Man after 11.35 ka BP.
