Fig. 6From: Calcareous nannofossil biostratigraphy of the Lower–Middle Pleistocene boundary of the GSSP, Chiba composite section in the Kokumoto Formation, Kazusa Group, central Japan, and implications for sea-surface environmental changesAge plots of the principal calcareous nannofossil taxa, Gephyrocapsa. This taxon is subdivided into size groups of < 3 μm, 3–4 μm, 4–5 μm, and ≥ 5 μm in diameter. The oxygen isotope curves of the CbCS (Haneda et al. 2020; Suganuma et al. 2018), and abundance of medium-sized Gephyrocapsa in the North Atlantic (Site 607) and the Mediterranean (Site 967) by Maiorano and Marino (2004) are also shown for comparison with size variations of Gephyrocapsa. Thin and thick lines of oxygen isotopes (Okada et al. 2017; Suganuma et al. 2018; Haneda et al. 2020) are measured data and 1000 year moving averages, respectivelyBack to article page