Radiometric Dating of tephras from Pre-caldera and Caldera-forming stages, Towada volcano, Northeast Japan.

Abstract

Takashi Kudo and Makoto Kobayashi (2013) Radiometric Dating of tephras from Pre-caldera and Caldera-forming stages, Towada volcano, Northeast Japan. Bull. Geol. Surv. Japan, vol. 64,, 2 figs, 2 tables.Abstract: Towada volcano is an active volcano located in the northern part of the Northeast Japan arc. We carried out fission-track (FT) and AMS radiocarbon ( 14 C) dating of tephras from Towada and Hakkoda volcanoes to establish a detailed eruptive history during the Pre-caldera and Caldera-forming stages of Towada volcano. The obtained FT ages were 0.23 ± 0.05 Ma for Shirobeta tephra (WP), 0.19 ± 0.05 Ma for T-6 tephra, 0.08 ± 0.03 Ma for Zarame 1 tephra (ZP1), and 0.09 ± 0.03 Ma for Okuse Pyroclastic Flow Deposits. Although these FT ages are consistent with stratigraphy, they have large error ranges of several tens of thousands of years. Therefore, further examinations including application of other chronological dating methods are necessary to obtain more precise estimates of the eruptive age of these tephras. The obtained 14 C age was 17,730 ± 70 BP for Biscuit 2 tephra (BP2). Based on stratigraphical consistency, this 14 C age is appropriate for the eruptive age of BP2.

Detection of Late Pleistocene tephras and cryptotephras using major element chemistry of glass shards from Chikyu C9001C cores, NW Pacific Ocean

“…5). The stratigraphy at location 3 has been reported by Kudo and Kobayashi (2013). Glass shards in samples 302, 303, 402, and 403, obtained by this study (Fig.…”

“…The heavy-mineral assemblage in samples 302, 303, 402 and 403 consisted of orthopyroxene. The eruption age of To-BP2 has been estimated to be slightly younger than 20.8-21.5 cal ky BP on the basis of the 14 C age of humic sediments just below To-BP2 (Kudo and Kobayashi, 2013).…”

“…1a and 1b. The 14 C age below To-BP2 at Location 3 is from Kudo and Kobayashi (2013). Tephra abbreviations not shown in Figure 2: On-Ng, Ontake-Nagawa; On-Kt, Ontake-Katamachi; SoP, Ontake-Shiojiri Pumice; On-Pm1, Ontake-Pumice 1; SUn, Sambe-Un'nan; To-HP, Towada-Hachinohe Pumice (the basal fall unit underlying the To-H pyroclastic flow deposits).…”

“…In the tephrostratigraphy in loess downwind of Towada volcano, To-H and To-BP2 are above To-Of (Machida and Arai, 2003). The eruption age of To-H has been estimated as 14.9-15.3 ka from the δ 18 O stratigraphy of deep-sea sediments (Aoki and Arai, 2000), whereas that of To-BP2 must be slightly younger than 20.5-21.5 cal ky BP, based on the 14 C age of humic sediments just below To-BP2 on the Kamikita Plain (Kudo and Kobayashi, 2013).…”

Thermoluminescence age determination for chemically selected samples of White Pumice tephra (WP) in the Kamikita plain, northeast Japan

“…1). WP has been used to establish Middle Pleistocene marine terrace chronology (Miyauchi, 1985(Miyauchi, , 1987Koike and Machida, 2001 ;Matsu'ura et al, 2014) and its reported ages scatter in a wide range, 280±50 ka (Kuwabara, 2007) and 230±50 ka (Kudo and Kobayashi, 2013) by fission-track method, and 160-200 ka (Miyachi, 1985) and 270 ka (Kudo et al, 2004) by stratigraphical evidences. Recently, WP has been estimated to correspond to mid marine isotopic stage (MIS) 7 (around 220 ka) by correlation with δ 18 O stratigraphy in deep-sea sediments (Chikyu C9001C cores) off Shimokita Peninsula (Matsu'ura et al, 2014).…”