Project Title: Variability of the British-Irish Ice Sheet in the Rockall Trough (North Atlantic) through ice-rafted debris and micro-faunal record.
Supervisors: Dr Sara Benetti and Dr Paul Dunlop
External advisors: Dr. Aggeliki Georgiopoulou (University College Dublin), Dr Shane Tyrrell (National University of Ireland, Galway); Dr Robin Edwards (Trinity College Dublin); Fabio Sacchetti (Marine Institute of Ireland)
Contact Details: s.benetti@ulster.ac.uk p.dunlop@ulster.ac.uk
Level: PhD
Background to the project:
The evolution of the northwest European continental margin was strongly affected by Pleistocene glaciations, particularly where ice sheets extended onto the continental shelf and transferred glaciogenic sediment onto the slope, contributing to the formation of canyon systems, submarine fans and slides (Sejrup et al., 2005; Ó Cofaigh et al., in press). Reconstruction of the history of the British-Irish Ice Sheet (BIIS) is difficult mainly due to stratigraphic and chronological uncertainties and the fact that sediments from older glaciations have often been eroded (Lee et al., 2011). Seismic reflection profiles from the Hebrides margin suggest significant expansions of the BIIS during each of the main glacial stages (Stoker et al., 1994). However, the low resolution and the poor age control preclude the clear distinction of individual advances (Sejrup et al., 2005).
Along the Porcupine Bank on the western continental margin of Ireland, multi-proxy foraminiferal and lithologic geochemical analyses have been used to document the variability of the BIIS in fine detail and to analyse its effect on oceanic circulation in the North Atlantic (Øvrebø et al., 2005; Peck et al., 2006; Peck et al., 2007).
This project will use a set of piston-cores (up to 4 m long) recently acquired from the western Irish margin (Fig. 1) to extend this reconstruction of BIIS variability along the Irish margin. The PhD project will focus on the characterisation, analysis and dating of sediments within the cores in order to investigate the delivery of glacially-derived sediment to the margin, in particular ice-rafted debris (IRD), and to investigate potential links to wider North Atlantic climate and ocean circulation.
Methods to be used:
The student will carry out a multidisciplinary investigation on a selection of available sediment cores including, but not limited to, the identification of fossil faunal populations and IRD record, analysis of stable isotope and trace metal composition of both sediment and fauna, and the age of significant horizons. The work flow will be the following:
1. Initial identification of sedimentary facies, by analogy with studies on other glaciated/glaciallyinfluenced margins (e.g. Canada, Mid-Atlantic USA, Antarctica).
2. Targeted sub-sampling and detailed analysis (grain size analysis, carbonate content, stable isotopes, dating and micro-faunal studies).
3. Determination of core chronologies and sedimentation rates using AMS radiocarbon dating, foraminifera stable isotopes and tephrochronology.
4. Identification of sediment infauna for the reconstruction of paleoenvironmental conditions.
5. Geochemical analysis of IRD grains.
Objectives of the research:
Specific objectives are:
• To assess the chronology for deep-water glacially-derived deposits;
• To quantify IRD fluxes to the margin, thus helping to constrain the timing of ice sheet advance and retreat across the Irish continental shelf;
• To reconstruct IRD provenance through geochemical analysis;
• To investigate the possible role of BIIS dynamics on the climate and ocean circulation of the North Atlantic.
Skills required of applicant:
The project will be suitable for a student with an Earth Sciences, Environmental Science or Marine Science background. The student may also have the opportunity to gain seagoing experience during the studentship.
