Fig. 5

Comparisons of magnetostratigraphy and ¹⁸⁷Os/¹⁸⁸Os records. a Depth variation of ¹⁸⁷Os/¹⁸⁸Os (Nozaki et al. 2019) together with inferred polarity zones of MR14-E02 PC11 for 5–12 m (Fig. 1). The inset is the ¹⁸⁷Os/¹⁸⁸Os for the entire core. A negative excursion at ~ 3.5 m was interpreted as a Miocene impact event (Nozaki et al. 2019). b Seawater ¹⁸⁷Os/¹⁸⁸Os data for 28–41 Ma together with the geomagnetic polarity time scale (Ogg 2012). The ¹⁸⁷Os/¹⁸⁸Os data are from ferromanganese crust (gray diamonds; Nielsen et al. 2009), pelagic clay (yellow open inverted triangles; Pegram and Turekian 1999), radiolarite and nannofossil ooze (filled circles; Dalai et al. 2006), and nannofossil and radiolarian ooze (open blue triangles; Paquay et al. 2008). The chronology of ferromanganese crust was based on the ¹⁸⁷Os/¹⁸⁸Os correlation to ~ 11–12 Ma, ~ 34.4 Ma, and ~ 55.5 Ma and linear interpolation between them with some adjustments. The chronology of pelagic clay is based on constant a Co flux model which may have 5–10 Myr offset in this interval (Kyte et al. 1993)