Provenance and flux of late quaternary sediment, Southeast Ireland

Abstract

The major sediment routing systems of Southeastern Ireland in the vicinity of the Leinster Massif were examined and quantified. Samples were taken from four of the major river systems, the Avoca, Barrow, Liffey and Slaney (along with, for the purposes of bedload investigation, the Vartry, a minor river system adjoining the Avoca and Liffey). Sand samples were also taken from beaches along the southeastern coast of Ireland, and samples from the Irish Sea seafloor were provided by the Geological Survey of Ireland (GSI). These samples were subjected to a variety of analytical techniques to determine whether the sands of the Irish Sea are derived from the Leinster Massif (provenance) and what is the total discharge of material per unit area being denuded from the area and being carried to the sea (flux). A total of 41 samples of Irish Sea sediment were provided by the GSI. In addition, 27 samples of beach sand and material from coastal tills were obtained, along with 53 samples of bedload sediment from the five rivers (six from the Avoca, three from the Vartry, eight from the Barrow, 15 from the Liffey and 21 from the Slaney). Each of these samples were analyzed granulometrically. The heavy mineral (detrital mineral species with specific gravity > 2.8) fractions of each sample in the grain size range between 250 and 63 μm were analyzed optically. Percentages of each heavy mineral type were ascertained for each river catchment, the beaches and the Irish Sea. Grains of detrital garnets were also isolated from each river and offshore and were examined for geochemical variations.