Using principal component analysis on regional soil geochemistry data sets to unravel former ice sheet history and gold dispersal in the north of Ireland

P Dunlop, Michael Dempster, Mark Cooper, A.J. Scheib

Research output: Contribution to conferencePoster

Abstract

Till geochemistry is largely determined by its parent bedrock and soils developed on tills are known to inherit this geochemical signature. Soil geochemistry from areas of till can therefore be used to establish glacial sediment provenance, which in turn provides information on palaeo ice flow direction and former ice sheet history. Here we present results of the first regional statistical analysis of soils developed on tills in the northern sector of the last Irish Ice Sheet. The study uses the Geological Survey of Northern Ireland Tellus geochemical database, which covers all of Northern Ireland and the contiguous Geological Survey of Ireland Tellus Border geochemical database that covers the adjacent border counties. A total of 5729 soil samples that occurred on till were extracted from both surveys and Principal Component Analysis (PCA), which is a multivariate statistical technique used to study variability in large geochemical data sets, was used to establish sediment provenance. PCA identifies a number of principal
components that allow identification of groups of related elements that together indicate a mineralogy, which in turn is used to locate the most likely bedrock source of the till. With reference to bedrock geology maps, the provenance of the sediment can then be determined and degree and direction of subglacial transport established. The results indicate that the upper surface of the majority of tills in the study area have a close relationship to local bedrock with
rapid geochemical changes observed at lithological boundaries. This suggests that tills in this sector of the former Irish Ice Sheet are primarily local in origin, indicating rapid entrainment of bedrock and low rates of evacuation of debris to the ice margin. In addition to investigating ice flow history, soil geochemistry can also be used for mineral prospecting in areas of thick subglacial deposits. However, this approach has not been widely used for the glaciated terrain of Ireland. Here we present the first results of applying PCA to the Tellus and Tellus Border soil geochemical data to investigate gold dispersal in the Southern Uplands - Down-Longford terrain in the north of Ireland. Multivariate statistical analysis of the data proves effective in identifying potential gold mineralisation, correlating well with and expanding on sources that have already been identified in the region. The results also indicate there was no significant glacial dispersal
of gold in the north of Ireland, in contrast to other glaciated terrains
Original languageEnglish
Pages35
Number of pages1
Publication statusPublished - 19 Aug 2015
EventCanadian Quaternary Association biennial meeting - Memorial University Newfoundland, St John's, Canada
Duration: 16 Aug 201519 Aug 2015
https://canqua2015.wordpress.com/

Conference

ConferenceCanadian Quaternary Association biennial meeting
Abbreviated titleCANQUA
CountryCanada
CitySt John's
Period16/08/1519/08/15
Internet address

Keywords

  • Tellus
  • Geochemistry
  • Till
  • British Irish Ice Sheet

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