Constraints on the frequency and dispersal of explosive eruptions at Sambe and Daisen volcanoes (South-West Japan Arc) from the distal Lake Suigetsu record (SG06 core)

Abstract

Accurately evaluating the tempo and magnitude of prehistoric eruptions is essential for hazard assessments. Here we demonstrate the importance of integrating records from locations close to the volcano with those in distal regions to generate more comprehensive event stratigraphies. The annually laminated (varved) and intensely radiocarbon dated lacustrine sediments of Lake Suigetsu (SG06 core), Japan are used to place chronological constraints on the tempo of volcanism at two stratovolcanoes located favourably upwind of the lake along the SouthWest Japan Arc, Sambe and Daisen. Major and trace element glass compositions are used to assign visible ash (tephra) layers preserved in the SG06 sediment core to past explosive eruptions from these volcanoes. Integrating these stratigraphies confirm that the ~150 ka long lake sequence records nine visible ash layers from Daisen and five from Sambe. The SG06 record captures two periods of closely spaced eruptions at Daisen volcano. The first period begins at ~61.9 ka with three explosive eruptions over ~10 ka, with two events separated by as little as 1.5 ka. One layer (SG06-4281), dated at 59.6 ± 5.4 ka (95.4% probability), relates to the large magnitude, and widely dispersed Daisen Kurayoshi Pumice (DKP) eruption. The other period of frequent activity began at 29,837 ± 96 IntCal13 yrs BP (95.4% probability) with five widely dispersed ash fall events associated with explosive eruptions separated by approximately 6, 936, 5 and 438 years. The integrated proximal-distal event stratigraphy and the high-precision SG06 chronology provide unique insights into the timing and frequency of past explosive volcanism from Daisen and Sambe, which has implications for the prediction of future eruption scenarios.

Major and trace element abundances in volcanic glass shards in visible tephras in SG93 and SG06 drillcore samples from Lake Suigetsu, central Japan, obtained using femtosecond LA–ICP–MS

“…The bimodal composition of SG06-4318 (B-22-03; Table S2) determined by Smith et al (2013) was not clearly detected in our study (SG93-48; Table S2). There are no significant differences in the trace element data for the Suigetsu samples correlated with the tephras that were obtained in our study and those presented by Albert et al (2018), (2019) (Fig. S1b).…”

“…The Suigetsu-Daisen and younger Suigetsu-Sambe samples, and layer B-21-04 correlated with SAN1/Kj-P1, have obvious Y depletion, high Sr/Y ratios, and HREE depletion relative to the other tephras (Figs. 2-4), as also noted by Albert et al (2018). These geochemical characteristics are typical of adakitic rocks (e.g., Defant et al, 1991;Martin et al, 2005).…”

“…Moreover, as noted by Albert et al . (), the K 2 O content of SG93‐46U (4.6 wt.%) is slightly higher than those of the other Suigetsu‐Sambe tephras (2.4 − 3.8 wt.%; Table S3). Layer A‐19‐04 (SI) has an elemental pattern intermediate between those of layer SG93‐46U and the other Suigetsu‐Sambe tephra samples.…”

“…), as also noted by Albert et al . (). These geochemical characteristics are typical of adakitic rocks (e.g., Defant et al ., ; Martin et al ., ).…”

“…An italicized layer name for core SG06 indicates that the corresponding layer from core SG93 was analyzed instead. SG06-1293 described in Smith et al (2013) and SG06-2535 described by Albert et al (2018) were not available for this study. †…”