Radiocarbon Evidence of the Age of an Irish Sea Glaciation in the Vale of Clwyd

Abstract

AS early as 1885 Strahan1 recognized the presence of two boulder clays of different derivation in the Vale of Clwyd. The mouth of the vale and lower Clwydian slopes are plastered to an upper limit of 600 feet OD (ordnance datum) with red till which has long been ascribed to an “Irish Sea Glaciation” because it is rich in erratics from the Lake District and southwest Scotland, together with brown flints and marine shells from the Irish Sea floor and contains no material of Welsh origin. The southern portion of the vale, however, contains an equally indisputable till, bearing an erratic suite of Ordovician and Silurian rocks obtained from the Arenig mountains and north-east Wales and exclusive of detritus of “Irish Sea” derivation, which is clearly the product of Welsh ice.