Our JEOL JXA iHP200F instrument is ideally configured for tephra analysis. Our new JEOL instrument preserves the exceptional capabilities for tephra analysis of its predecessor, the Cameca SX100. Developments in tephra analysis and preparation at Edinburgh (Hayward, 2012; Hall and Hayward 2015) enable analysis of very fine-grained distal tephra grains down to 10-15 microns or less across. Tephra compositions represent the wide spectrum of erupted magmatic compositions and subsequent duration and environment of burial.The geological setting of individual volcanic centres differ from one another, thus each produces tephra with distinct compositional ranges. Because each erupted magma batch has a unique history, chemical distinctiveness extends to tephras from the individual eruptions of one volcano. Matching of compositions of proximal and distal tephra layers enables the identification of specific eruptions within stratigraphic records including peat bogs, soils, lacustrine deposits, ice cores and marine sediment cores.As tephra fallout produces isochrons within sedimentary sequences, tephras from eruptions dated by absolute methods such as 14C or by historical observation create tephrochronological frameworks across areas of preserved fallout. Tephrostratigraphy remains important even in regions lacking chemical analyses of source volcano proximal sequences or absolute dating, by providing a relative framework for correlation of distal tephras between different locations. Developments at Edinburgh have extended the geographical range of tephrochronological frameworks by enabling analysis of the most distal, fine-grained tephras.Geochemical fingerprinting of tephras is achieved reliably electron probe microanalysis (EPMA). Discrimination between the majority of tephra layers in any region is achieved by analysis of ten major and minor elements (Na, Mg, Al, Si, P, K, Ca, Ti, Mn, Fe). Each analysis requires 5-7 minutes, depending on electron beam diameter, and most tephra layers can be reliably identified with 15-25 analyses. Tephrochronology by EPMA is thus rapid and cost-effective. Analysis of the volatile elements S, Cl and F by EPMA permits understanding of the degassing of sulphur and halogens from magma during ascent in the crust to final eruption. This enables evaluation of atmospheric and environmental impacts caused by volcanism. Volatiles such as water and carbon dioxide can be measured by the School’s NERC Ion Micro-Probe (SIMS) Facility and trace elements such as REEs, Zr and Nb by our LA-ICP-MS Facility.View NERC Ion Micro-Probe (SIMS) Facility webpageView Brian Price ICP Facility webpageVarious on-line databases of tephra composition and eruption dates, compiled from published literature, are available to assist with the identification of source volcanoes and individual eruptions. Edinburgh hosts the Tephrabase website.Tephrabase website This article was published on Monday 1 July 2024
