Morphological and Chemical Variations of a Buried Palaeocatena in Late Holocene Beach-ridge Sands at Magilligan Foreland, Northern Ireland

Abstract

Vertical and horizontal variations in soil profile morphology and chemistry within a sequence of buried palaeosols developed in Late Holocene beach-ridge sands at Magilligan Foreland indicate the existence of a palaeocatena. A humus podzol occurs on the crest of the beach ridge and passes through a gleyic brown calcareous alluvial soil and a typical humic alluvial gley soil to a raw en-fibrous peat soil in the inter-ridge depression. This sequence reflects different slope positions and soil water regimes. Water-table fluctuations, possibly associated with Late Holocene sea-level oscillations, have combined with pedogenic processes to produce the distinctive morphology and chemistry of the palaeocatena. All palaeosols have developed in texturally uniform sands and have been decalcified to depths of between at least 0.85 m to 1.6 m. Ferruginous concentrations, present in the lower horizons of each palaeosol, formed after the profiles were decalcified. Palaeocatena development was probably restricted to a time-span of c. 1,000 years to 1500 years. Two aeolian sand units bury the palaeocatena; the older of these has been 'welded', in part, to the palaeocatena by pedogenic processes. Percolation of water through the younger calcareous aeolian sand unit can account for the present near-neutral pH values of the palaeocatena.