Fig. 8

Comparison of the M–B boundary observed from the Chiba composite section and the TB-2 sediment core. VGP latitudes based on thermal demagnetization in Suganuma et al. (2015) are shown as blue cross marks. VGP latitudes based on the hybrid demagnetization method are shown as black closed circles and lines (Okada et al. 2017) and red open circles and lines (this study). The TB-2 sediment core was drilled 190 m northeast of the Chiba section, and VGPs obtained from the core as reported by Hyodo et al. (2016) are shown as blue closed circles and lines (AFD) and red closed circles and lines (ThD). Lithology of the TB-2 sediment core was from Hyodo et al. (2016, 2017). Blue, black, and red horizontal bars indicate the sampling level of Suganuma et al. (2015), Okada et al. (2017), and this study, respectively. Black and red dashed lines show the mid-thickness of polarity switch indicating the M–B boundary and the correlation of the volcanic ash