The glaciations of the Conway Catchment, north Wales
Fishwick, A. B.
PublisherUniversity College London (University of London)
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The aim of this thesis has been to establish the patterns of ice movement in the Conway catchment and the relationships between Welsh and Irish Sea ice on the coast. Work has concentrated on analyses of till particle sizes, lithologies and fabrics (84 samples from inland and 56 from coastal exposures), supplemented by information from boreholes (c. 300)t meltwater channels and erosional and depositional landforms. Trend surface, cluster and factor analyses have been used where appropriate to synthesise till data. A north-eastwards flow of ice in the south paralleling the upper Conway and Machno valleys, points to an ice shed running north-westwards from Migneint to the head of the Lledr valley. The north-north-eastwards flow off the Carneddau. indicates these mountains also acted as an important source of ice. The northwards flow of ice along the eastern margin of the Vale is attributed to the influence of the marked topography of the Vale. The evidence does not favour an ice cap on the Denbighshire Moors. The distribution of meltwater channels and till suggests that ice overtopped the eastern watershed of the catchment during the last glaciation. The uppermost till on the coast is the distinctive Red Irish Sea till which is found as far South as Llansantffraid Glan Conway and on Great Ormes Head at a height of 190 m (620 ft). in coastal exposures it is underlain by Welsh and Irish Sea tills. No direct evidence of the age or the time intervals between successive tills is available but there is nothing to suggest they are not Devensian in age. The possibilities that the local sequence demonstrates a readvance or alternatively conflicts between Welsh and Irish Sea glaciers are explored, and tentative correlations drawn with sequences described in adjacent areas.