Use this URL to cite or link to this record in EThOS: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.780460
Title: Establishing a detailed tephrochronological framework for Japan to aid the synchronisation of palaeoenvironmental records across the Asian/Pacific region
Author: McLean, Danielle
ISNI:       0000 0004 7966 102X
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2018
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Abstract:
Tephra (volcanic ash) layers have the potential to synchronise palaeoenvironmental archives across regional to hemispheric scales. Highly productive arc regions, like those in East Asia, offer a considerable number of widespread isochrons, but before records can be confidently correlated using these layers, a refined and integrated tephrochronological framework is required. The Lake Suigetsu sequence, obtained from a small tectonic lake in central Honshu, is the most precisely dated sedimentary record for Japan. Here, the sediments are examined for the presence of thin (sub-millimetre in thickness) and 'non-visible' (cryptotephra) layers in order to provide a comprehensive record of East Asian volcanism, and a linchpin site for correlating sequences. On average, cryptotephra layers are identified four times more frequently than visible markers in the studied sediments of Lake Suigetsu, providing an unprecedented record of ash fall events that reached the densely populated regions of central Honshu. Major and trace element glass geochemistry obtained from these tephra layers is compared to new and published datasets to pinpoint their volcanic source. The cryptotephra were erupted from sources that span the length of Japan, and volcanoes further west, including Ulleungdo (South Korea) and Changbaishan (North Korea/China). Constrained eruption ages are modelled for the tephra layers identified in the sequence, which can be transferred into other sedimentary records that contain these markers. Cryptotephra identifications show that many eruptions dispersed ash more widely than previously anticipated, and are able to synchronise palaeoclimate records over hemispheric scales. For example, the archive provides the most southerly tephra occurrence of the B-Tm tephra, synchronising this mid-latitude record to the Greenland ice cores. The augmented Lake Suigetsu eruption archive is established as a key node within the tephrostratigraphic framework for Japan, and provides an important resource for volcanological research, with constraints on the frequency, reoccurrence intervals and dispersal of numerous eruption events.
Supervisor: Smith, Victoria ; Albert, Paul Sponsor: Natural Environment Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.780460  DOI: Not available
Keywords: Quaternary Science ; Geochronology ; Volcanology ; Earth Sciences ; Palaeoclimatology
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