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Records of Katla's explosive past preserved in archaeological contexts and fossil beaches in Norway

Anke Verena Zernack 1, Erlend Kirkeng Jørgensen2, Anthony Newton3, Anders Romundset4

  • Affiliations: 1Volcanic Risk Solutions, Massey University, Palmerston North, New Zealand; 2Norwegian Institute of Cultural Heritage Research, Tromsø, Norway; 3School of Geosciences, University of Edinburgh, Edinburgh, United Kingdom; 4Norwegian Geological Survey, Trondheim, Norway 

  • Presentation type: Poster

  • Presentation time: Tuesday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 138

  • Programme No: 3.13.7

  • Theme 3 > Session 13

Abstract

Ocean-rafted pumice from Iceland is found in archaeological sites and on modern and paleo-beaches across the North Atlantic. While not as accurate as tephrochronology, ocean-rafting events can be fingerprinted to their volcanic source and contribute to dating coastal sedimentary records and landforms, including archaeological sites. They also provide records of large explosive eruptions that might not be preserved near the volcano and as such can be used for petrological and geochemical investigations. We focused on beach and archaeological pumices from Norway to better understand the nature and frequency of Holocene silicic eruptions from Katla, while also improving age control for shoreline displacement reconstructions and archaeological contexts. Pumice was found on several levels of raised shorelines along the Varanger and Trøndelag coast, reflecting deposition and subsequent preservation at certain times and in specific settings. Glass compositions of pumice samples form a continuous array that mostly overlaps with the <7.2 ka SILK-tephras from Katla, with one sample plotting outside the Katla field and resembling compositions known for Jan Mayen. Despite some finds in Mesolithic contexts, older eruptives were not found on Early Holocene beach ridges. Pumice availability also varied with climate, being readily accessible in cold bare landscapes but getting covered by peat and vegetation in milder conditions. This is supported by our archaeological data, which suggests access to individual pumice batches becoming limited within hundreds to 2-3,000 years following eruption, rafting and onshore deposition. Our study shows that ocean-rafted pumice provides valuable archives and opportunities for volcanological, geological and archaeological investigations.