Analytical data of zircons from tephra in the Oshamambe district（Kuromatsunai lowland）, southwestern Hokkaido

Fig. S1. Outcrop photographs of the sampled tephras. (a)CRGW, (b) CRG_SS, (c) ST-PF. Yellow dashed rectangles (height of rectangles: ~30 cm) denote where samples were collected. Table S1. Zircon U–Pb dating results. Data marked with #(>75% common Pb contamination) were excluded for further U–Pb analyses. CRGW (sampling location coordinates: 42.616478,140.316706) measured on 09/30/2020, 10/29/2020 CRG_SS (sampling location coordinates: 42.607056,140.314058) measured on 09/30/2020 ST-PF (sampling location coordinates: 42.618414,140.325478) measured on 07/06/2021 Bishop Tuff (reference age: 0.767±0.001 Ma; Crowley et al., 2007) measured on 09/30/2020, 10/29/2020, 07/06/2021 Fish Canyon Tuff (reference age: 28.402 ± 0.023 Ma; Schmitz and Bowring, 2001) measured on 09/30/2020, 07/06/2021 Plešovice (reference age: 337.13±0.37 Ma; Sláma et al., 2008) measured on 09/30/2020, 10/29/2020, 07/06/2021 a_fTh/U = (Th/U)zircon/(Th/U)magma. (Th/U)magma of 4.0 ± 2.0 for unknown, 3.0 ± 1.5 for Bishop Tuff, and 2.2 ± 1.1 for Fish Canyon Tuff were used. b_f206% denotes the percentage of 206Pb that is common Pb and is calculated as follows: f206% = 100 × (x－0.0461)/(0.832－0.0461), where x is a measured 207Pb/206Pb ratio (Ito et al., 2017). c_Measured isotope ratio, that is before corrections of initial 230Th and 231Pa disequilibrium and common Pb. d_Individual U-Pb (238U-206Pb) ages were determined using the modified 207Pb method (Sakata, 2018). Error of weighted mean is shown as 95% confidence level. e_MSWD: mean square weighted deviation. f_Statistical outlier identified by applying 2σ criterion in Isoplot (Ludwig, 2012). References Ito, H., Spencer, C.J., Danišík, M., Hoiland, C.W., 2017. Magmatic tempo of Earth’s youngest exposed plutons as revealed by detrital zircon U-Pb geochronology. Scientific Reports, 7: 12457. Ludwig K.R., 2012. User’s Manual for Isoplot 3.75: A geochronological toolkit for Microsoft Excel. Berkeley Geochronol. Center Spec. Pub., 5, 75 pp. Sakata, S., 2018. A practical method for calculating the U-Pb age of Quaternary zircon: Correction for common Pb and initial disequilibria. Geochem. J., 52, 281–286. Table S2. Zircon (U–Th)/He analytical results and parameters used for the disequilibrium correction. TAU - total analytical uncertainty; Raw He age - (U-Th)/He age uncorrected for alpha ejection; Ft - alpha ejection correction factor after Farley et al. (1996); D(230) - parameter describing zircon-melt fractionation of 230Th/238U (Farley et al., 2002; Schmitt et al., 2010) calculated as (Th/U)zircon/(Th/U)magma, whereby a value of 4 was used for (Th/U)magma and a value of 3.8 was used as D(231) (Schmitt, 2011); Diseq.-cor. He age - (U-Th)/He age corrected for disequilibrium calculated by using MCHeCalc software (Schmitt et al. 2010). References: Farley, K.A., Kohn, B.P. and Pillans, B., 2002. The effects of secular disequilibrium on (U–Th)/He systematics and dating of Quaternary volcanic zircon and apatite. Earth Planet. Sci. Lett., 201, 117–125. Farley, K.A., Wolf, R.A. and Silver, L.T., 1996. The effects of long alpha-stopping distances on (U-Th)/He ages. Geochim. Cosmochim. Acta, 60, 4223-4229. Schmitt, A.K., 2011. Uranium series accessory crystal dating of magmatic processes. Annu. Rev. Earth Planet. Sci. 39, 321–349. Schmitt, A.K., Stockli, D.F., Niedermann, S., Lovera, O.M. and Hausback, B.P., 2010. Eruption ages of Las Tres Vírgenes volcano (Baja California): a tale of two helium isotopes. Quat. Geochronol., 5, 503–511.