Development and age structure of Holocene coastal sand dunes at Horn Head,near Dunfanaghy,Co Donegal,Ireland

Two areas of Holocene coastal sand dunes on the western side of the Horn Head peninsula extend from low ground immediately inland of their respective source beaches onto flanking higher ground (> 100 m OD). Stratigraphic investigations supported by ¹⁴C dating of buried organic-rich horizons and shells demonstrate several phases of sand accumulation in the Pollaguill-Croaghadara system in contrast to the larger Tramore-Anloge Hill system, where the available evidence points to relatively recent dune emplacement. A broadly synchronous phase of dune development occurred during the thirteenth to fourteenth centuries AD and is viewed as part of a regional (northwestern Europe) dune-building episode resulting from climatic deterio ration. Earlier phases (pre-3300-2800 ¹⁴C years BP) of aeolian sand deposition at Pollaguill-Croaghadara have no apparent equivalents at Tramore-Anloge Hill and repeated fluvial incision and sand reworking during the last 2000 ¹⁴C years is also evident at the former site. Dated organic horizons, in combination with site location, sand source and transport direction, suggest the earliest phase of aeolian sand accumulation and subsequent stabilization was time-transgressive. The respective roles of relative sea-level change, climatic change and anthropogenic influence in dune evolution are difficult to evaluate in the absence of detailed information, although documentary evidence indicates human-induced destabilization of the Tramore-Anloge Hill dunes during the 1920s and 1930s. Thus, despite similar topographic settings and close proximity, the dunes do not share entirely similar histories and caution against the development of regional dune chronologies from investi gations of single systems. The observations and data suggest that a mix of local and regional controls have combined in the construction of these dunes.