Developing a Holocene tephrostratigraphy for northern Japan using the sedimentary record from Lake Kushu, Rebun Island

Xuanyu Chen, Danielle Mclean, Simon Blockley, Pavel Tarasov, Yi-Gang Xu, Martin Menzies

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Palaeoclimate records in East Asia offer significant potential to further our understanding of monsoon dynamics and can serve as a link between North Atlantic and tropical climate systems. The sedimentary core from Lake Kushu, Rebun Island, provides the first high-resolution palaeoclimate record from northern Japan. In order for this regionally significant archive to be synchronised to other records, and to generate a more detailed Holocene tephra lattice for East Asia, we present the first cryptotephra stratigraphy for northern Japan using the Kushu RK12 core. The detailed RK12 tephrostratigraphy integrates local and far-travelled tephras originating from Japan, Russia, China/North Korea and most likely Indonesia. Five key cryptotephra layers have been identified, precisely dated and correlated to the specific eruptions or the source region (B-Tm tephra – Changbaishan volcano; SH#12 tephra – Shiveluch volcano; Ko-g tephra – Komagatake volcano; Ma-f ∼ j tephra – Mashu volcano and RK12-0819 tephra with possible Indonesian origin). These tephra horizons are very widely dispersed, providing opportunities to synchronise distant palaeoclimate records from the polar region, through high northern latitudes to the tropics, which facilitate interregional comparison of palaeoclimate and environmental data. In addition, a number of the geochemically analysed horizons contain other minor numbers of compositionally distinct glass, which can also be grouped and correlated to their source volcanoes. These minor analyses are of interest since they provide new insight into regional tephra dispersal (e.g., ash dispersal potential of Aira and Towada), and could suggest that there are other potential eruptions that have yet to be identified in the geological record (e.g., potential Changbaishan eruptions). The integrated Lake Kushu cryptotephra record extends the ash dispersal of several key tephra horizons in the region. The presence of the Shiveluch SH#12 tephra in Lake Kushu (ca. 1900 km away), documents the first example of a Russian tephra reaching the Japanese Archipelago. Furthermore, glass compositions suggest that the core could preserve an eruption event derived from Indonesia, highlighting the future possibility to significantly extend and interlink the tephra lattice across the entirety of Asia. This is an essential step for the understanding of how climate changes propagate over large geographical areas. Indeed, several of these tephra markers coincide with significant ecological changes reflected in the pollen proxy record at Lake Kushu. Using this high-resolution palaeoenvironmental record, we however find no significant ecological impact following the large late Holocene “Millennium Eruption” from Changbaishan, China/North Korea.
Original languageEnglish
Pages (from-to)272-292
Number of pages21
JournalQuaternary Science Reviews
Early online date1 Jun 2019
Publication statusPublished - 1 Jul 2019

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