An assessment of discriminant function analysis in the identification and correlation of distal Icelandic tephras in the British Isles

This paper is part of the special publication No.161, Volcanoes in the Quaternary (eds: C.R. Firth and W.J. McGuire). This paper assesses the potential of discriminant function analysis (DFA) for tephrochronology in the UK and Ireland. Current identification and correlation of Holocene tephras relies largely on radiocarbon dating to suggest a likely candidate eruption followed by a geochemical comparison using binary and ternary plots of selected major oxides. As more tephras are discovered, and the patterns of deposition appear increasingly complex, this approach is likely to work less effectively. In addition, the utility of tephra for the establishment of chronozones will be limited by the availability of radiometric dates to constrain the initial candidate eruption. The results of a DFA on some of the limited published geochemical data are presented and it is clear that this statistical technique offers advantages to the application and development of tephrochronology in western Europe. Future work should concentrate on the provision of discriminant functions from a more complete reference dataset, which will enable the identification of unknown tephras with a known probability of misclassification.