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Itrax μ-XRF core scanning for rapid tephrostratigraphic analysis: a case study from the Auckland Volcanic Field maar lakes
Authors:Leonie Peti  Patricia S Gadd  Jenni L Hopkins  Paul C Augustinus
Institution:1. School of Environment, the University of Auckland, New Zealand;2. Australian Nuclear Science and Technology Organization, Sydney, Australia;3. School of Geography, Environment and Earth Sciences, Victoria University of Wellington, New Zealand
Abstract:Itrax micro X-ray fluorescence (μ-XRF) core scanning is a non-destructive, rapid approach to measuring elemental concentrations and their variability in sediment cores. As such, it records elemental signatures of tephra layers, which serve as correlation tie points and chronological markers for these sedimentary archives of past climatic changes. The traditional tephra identification approach using electron microprobe-based geochemical fingerprinting of glass shards is a slow and invasive process, whilst μ-XRF scanning of rhyolite tephra in sediment cores from Auckland (New Zealand) could provide a faster, non-invasive approach to aid the recognition of tephra layers. This study highlights the potential and pitfalls in this novel approach: changes in most scanning parameters, and the use of two different Itrax core scanners, still led to similar chemical characterizations of the tephra layers. Changes in other scanning parameters have a biasing influence on the chemical characterization of the tephra, which would lead to misidentification of unknown layers. We demonstrate that μ-XRF core scanning provides a faster and non-invasive approach to correlation of sediment sequences using chemically distinct, visually pure tephra layers if a strict scanning protocol is followed. Nevertheless, an extensive database of μ-XRF-scanned rhyolite tephra is required for recognition of unknown tephra units using this approach.
Keywords:electron probe microanalysis  micro-XRF  New Zealand  tephrochronology  volcanic ash
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