Fig. 7

Outcrops of a–e pebbly sandstone beds covering the major erosional surface and f, g coeval MTDs (mass-transport deposits) formed at around 3.2 Ma. a–e A poorly-sorted pebbly sandstone with mud clasts on the major erosional surface exposed at section F3 in Seki a, b on the western Boso Peninsula, c, d at section K1 on the eastern Boso Peninsula, and e section Z1 on the Miura Peninsula. See Figs. 3, 5c, 6 for the localities. f, g Mass-transport deposits exposed f in Nagasaki on the western Boso Peninsula and g along traverse 3 on the Miura Peninsula. See Fig. 5 and Utsunomiya et al. (2017) for the localities. Blue arrows in b, d and e indicate the major erosional surface. White arrows in d and e indicate the mud clasts