A catalogue of major and trace element data for Icelandic Holocene silicic tephra layers

Abstract

Tephra layers with Icelandic provenance have been identified across the North Atlantic region in terrestrial, lacustrine, marine and glacial environments. These tephra layers are used as marker horizons in tephrochronology including climate studies, archaeology and environmental change. The major element chemistries of 19 proximally deposited Holocene Icelandic silicic tephra layers confirm that individual volcanic systems have unique geochemical signatures and that eruptions from the same system can often be distinguished. In addition, glass trace element chemistry highlights subtle geochemical variations between tephra layers which appear to have identical major element chemistry and thus allows for the identification of some, if not all, tephra layers previously considered identical in composition. This paper catalogues the compositional variation between the widespread Holocene Icelandic silicic tephra deposits.

A shift in eruption mode of Hekla volcano, Iceland, 3000 years ago: two‐coloured Hekla tephra series, characteristics, dispersal and age

“…The pale units are andesite–dacites with 61.1–64.2% SiO 2 and the dark units basaltic andesites with 52.7–58.2% SiO 2 . The apparent jump of 4–8% SiO 2 between the dark and pale units is larger here than in the EPMA analyses on the TC‐tephra layers by Meara () and Róbertsdóttir et al . (, unpublished data) where it is about 2% (between 60.5 and 58.5% SiO 2 ) in more detailed sampling across the boundary zone.…”

“…EPMA analyses of TC‐tephra in distal settings in Iceland are presented in supplementary table S1 in Óladóttir (). For detailed geochemistry of the TC‐tephra layers see Meara ().…”

“…Meara () concluded from her EPMA and XRF analyses that the TC‐tephra layers could not be distinguished by major elements. We do not contest this, and the slight differences in composition between individual TC‐layers in Table may at least partly be caused by the sampling.…”

“…Jónsson, ). Detailed electron probe micro‐analysis (EPMA) geochemistry of the TC‐tephra layers has already been carried out by Meara ().…”

“…The largest of these post‐Hekla‐3 eruptions have been briefly described, including dispersal, preliminary volumes and geochemistry (Larsen and Vilmundardóttir, ; Róbertsdóttir, ; Larsen et al ., ; Róbertsdóttir et al ., ; Larsen and Eiríksson, ). More recently, detailed analysis of their geochemistry has been carried out (Meara, ; Meara et al ., this volume).…”