Holocene coastal evolution, Co. Donegal, Ireland John Shaw

Abstract

Within the context of an interdisciplinary project concerned with coastal evolution in County Donegal, Ireland, an area of little previous research, three main aspects were examined. Firstly, the nature of the intertidal peats in this area and the information they contain on relative sea-level change. Secondly, the nature of the coastal sediment systems and thirdly, the evolution of these during the Holocene in the light of relative sea-level changes.

The research showed that intertidal peat in the study area has formed under varying conditions, and in some areas, where it rests on estuarine sediments, regressive overlap is indicated. 14C dating, corroborated by pollen analysis, was used to construct a tentative RSL framework. A mid-Holocene RSL peak in the northeast is absent in the southwest. Relative sea level curves for the study area form a continuum which, it is suggested, is part of a larger British Isles continuum. Systems of coastal dunes, fronted by high energy beaches, are located in compartments or at the mouths of shallow estuaries. In the latter situation, sediment, typically carbonate-rich fine sand, is circulated through a number of environments: dunes, estuaries, ebb deltas, beaches and the offshore zone. The release of sediment from dune sinks is accomplished by migrating ebb channels. Sediment is moved into new sinks, typically systems of prograded dune ridges.

It is suggested that most coastal sediment systems formed as the mid-Holocene RSL rise waned. Initial phases of gravel emplacement, sometimes drift-orientated, were succeeded by phases of dune ridge progradation and vertical growth. The second half of the Holocene, a period of relatively stable RSL, was characterised by the continued feeding ashore of sand, augmented by skeletal carbonate, into the dunes.

Date of Award	1985
Original language	English