Proximal–distal fall deposit correlation of VEI‐5 tephra (Towada‐Chuseri) from Towada volcano, northeast Japan

Abstract

A tephra layer offers an isochronous surface in sediments, thus serving as a key bed and/or an age marker. Recent high-resolution sediment research (e.g. varved sediments) has revealed optically invisible tephra fingerprints and provided high-precision tephra ages. However, a tephra-based correlation cannot succeed without detailed knowledge of the tephra characteristics in a proximal area to correlate with tephra in high-resolution sediments in remote areas. Here we documented the detailed characteristics of Towada-Chuseri (To-Cu) tephra, which is associated with the Middle Holocene volcanic explosivity index 5 eruption of Towada volcano, northeast Japan. We used To-Cu tephra samples to achieve the proximal-distal correlation of three members: Chuseri pumice (Cu), Kanegasawa pumice (Kn) and Utarube ash (Ut). These distal occurrences correlate with proximal To-Cu tephra based on volcanic glass morphology and refractive index, as well as on major element composition of volcanic glass shards. Refractive indices allow the preliminary correlation of each member, and major element composition helps in distinguishing Ut from the other members. Glass morphology provides additional support. These correlations reveal that To-Cu, especially Cu, covered central to northeast Japan while confirming that To-Cu is the representative tephra in the Middle Holocene of the Tohoku region.

~5.9 cal ka bp Towada‐Chuseri tephra from Towada volcano: a mid‐Holocene marker layer from Japan to northeast China

“…Considering other coincident large explosive (volcanic explosivity index: VEI > 5) eruptions from southeast to east Asia that have widespread tephra dispersals, there are also some potential source candidates for GST‐314: the 7307–7196 cal a bp Kikai‐Akahoya eruption (K‐Ah, Kikai volcano, Japan), the 6079–5004 cal a bp Pinatubo (Philippines) eruption, the 4894–4827 cal a bp SG14‐0704 tephra recorded in Lake Suigetsu (unknown eruption), the 7340–7180 cal a bp KS 2 tephra from Ksudach caldera (Russia), the 6375–6220 cal a bp IAv12 (AV 4 ) tephra from Avachinsky volcano (Russia), the 7920–7620 cal a bp KHG tephra from Khangar volcano (Russia) and the 5986–5899 cal a bp Towada‐Chuseri eruption (To‐Cu, Towada volcano, Japan) (Ishimura and Hiramine 2020; McLean et al ., 2018; Plunkett et al ., 2015; Ponomareva et al ., 2017; Portnyagin et al ., 2020; Smith et al ., 2013; Sun et al ., 2021). Geochemically, the GST‐314 tephra has a diagnostic glass composition with low potassium content and high silicon content which is consistent only with the To‐Cu tephra and clearly separable from other broadly contemporary tephras (Figs.…”

“…The To‐Cu eruption has been attributed a VEI of 5 based on a total estimated tephra volume of 9.18 km 3 (Hayakawa, 1985; Newhall and Self 1982). To‐Cu can be divided into three units: Chuseri pumice (Cu), Kanegasawa pumice (Kn) and Utarube ash (Ut), of which the Cu pumice is the lowermost bed and most widely distributed (Hayakawa, 1985; Ishimura and Hiramine 2020). While there is some overlap in their glass composition, Ishimura and Hiramine (2020) have shown that the units are separable on the basis of shard morphology and major element geochemistry, especially Ut, the youngest unit which is the product of phreatic eruptions.…”

“…To‐Cu can be divided into three units: Chuseri pumice (Cu), Kanegasawa pumice (Kn) and Utarube ash (Ut), of which the Cu pumice is the lowermost bed and most widely distributed (Hayakawa, 1985; Ishimura and Hiramine 2020). While there is some overlap in their glass composition, Ishimura and Hiramine (2020) have shown that the units are separable on the basis of shard morphology and major element geochemistry, especially Ut, the youngest unit which is the product of phreatic eruptions. On the basis of previous investigations, To‐Cu dispersal was mainly towards the south of Towada, and tephra has been identified in various sedimentary archives, the most distal occurrence being in Lake Suigetsu ~700 km southwest of the vent (Hirose et al ., 2014; Ishimura et al ., 2017; Kariya et al ., 2016; McLean et al ., 2018).…”

Crossing new frontiers: extending tephrochronology as a global geoscientific research tool

“…(23) (15) South East Asia (Bouvet de la Maisonneuve and Bergal-Kuvikas (2020) (16) Aira caldera, Japan (Nishizawa and Suzuki, 2020) (17) Aso caldera, Japan (Miyabuchi and Sugiyama, 2020) (18) Lake Suigetsu, Japan (Maruyama et al, 2020) (19) Tohoku area, Japan (Suzuki et al, 2020) (20) Towada volcano, Japan (Ishimura and Hiramine, 2020) (21) Kamchatka Peninsula, Russia (Zelenin et al, 2020) (22) Meiji Rise, NW Pacific Ocean (Derkachev et al, 2020) (23) Auckland Volcanic Field, New Zealand (Peti et al, 2020) show that the eruptives can be distinguished using their glass geochemistry, thereby providing a key reference dataset to aid the identification of distal deposits.…”

“…The proximal–distal correlations permitted the assessment of magnitudes of the eruptions depositing the tephras, with evidence provided for two closely spaced VEI 7 eruptions, within less than 200 kyrs, from the Sengan geothermal region. Ishimura and Hiramine (2020) also focusses on the proximal–distal correlation of a tephra from northeastern Japan, but for a more recent eruption, the mid‐Holocene Towada‐Chuseri (To‐Cu) tephra that has recently been dated to 5986–5899 cal a bp based on its distal occurrence in Lake Suigetsu (McLean et al ., 2018). Through the acquisition of glass morphology, refractive index and major element compositional data from a large number of distal deposits, three members could be correlated to the proximal To‐Cu tephra.…”