Amino acid evidence for Devensian ice, west Gower, South Wales

Abstract

Complete inundation of South Wales by ice during the penultimate (Wolstonian?) glaciation has been widely suggested^1–3. Although it is generally agreed that the last glaciation was less extensive than the preceding one^4–6, there has been controversy concerning its limits, stemming mainly from the lack of clear geomorphological evidence and the dearth of datable material^7–9. ¹⁴C dates from the shelly till in Pembrokeshire were first thought to indicate an extension of last glaciation ice into the area¹⁰, but serious doubts were subsequently raised about the reliability of finite dates on shells of this age range^11,12. We present here results of amino acid analysis of shells from recently exposed till and from underlying raised beach remnants at Broughton Bay, west Gower. Total D allo : L iso ratios from the raised beach are consistent with analyses on shells from comparative beach remnants elsewhere in south-west Britain^7,13–15. Shells of 21 identifiable littoral species extracted from the till suggest inshore marine conditions similar to those at present. Amino acid ratios from Littorina spp. provide firm evidence for the encroachment of Devensian ice on to Gower, approximately to the limit suggested by Bowen⁷ (Fig. 1a).