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Constraints on the timing of East Asian explosive volcanism: insights from cryptotephra deposits preserved in marine and lacustrine archives

Paul Albert1, Gwydion Jones1, Sophie Vineberg2, Victoria Smith2, Emma Watts1, Danielle McLean2, Victoria Cullen2, Ken Ikehara3, Richard Staff2, Takehiko Suzuki4, Hannah Buckland1, Takeshi Nakagawa5, Takuya Sagawa6

  • Affiliations: 1Department of Geography, Swansea University, Swansea, UK; 2School of Archaeology, University of Oxford, Oxford, UK. 3Geological Survey of Japan, AIST, Tsukuba, Japan; 4Department of Geography, Tokyo Metropolitan University, Tokyo, Japan; 5Research Centre for Palaeoclimatology, Ritsumeikan University, Kusatsu, Japan; 6Institute of Science and Engineering, Kanazawa University, Kanazawa, Japan.

  • Presentation type: Talk

  • Presentation time: Tuesday 09:00 - 09:15, Room S150

  • Programme No: 3.13.3

  • Theme 3 > Session 13

Abstract

Volcanic hazard assessments are in part constrained by understanding the past behaviour of a volcano (e.g., eruptive frequency and magnitude), this is largely reconstructed using tephra deposits preserved close to source. However, these near-vent eruption records are often fragmentary and incomplete owing to burial and erosion processes, thus potentially hampering the accuracy of hazard assessments. Here we capitalise on the potential of long, undisturbed records of ash fall events preserved in East Asian marine and lacustrine sedimentary archives, typically positioned >100 km from volcanic sources, to plug the gaps in near-source eruption records. The extraction and identification of microscopic ash layers (cryptotephra) from sedimentary archives is adopted to provide important constraints on the timing of mid-intensity explosive eruptions which are frequently under-reported at source. Following detailed cryptotephra investigations we present a new eruption record captured by high-resolution sediment cores (WB06 and WB08) from off the Wakasa Bay (Sea of Japan), which span the last 100,000 years. Detailed geochemical fingerprinting is used to assign >30 tephra and cryptotephra deposits to volcanic source, and where possible to known eruptions. Furthermore, these chemical signatures are used to link the WB06 and WB08 tephra layers to those preserved in the precisely dated sediments of Lake Suigetsu (Honshu Island), providing important chronological constraints on this newly developed eruption record. Our investigations provide evidence of near-vent under-reporting (or grouping) of explosive eruptions and new insights into the repose periods between pre-historic eruptions at individual volcanoes.