Fig 1.
Fossilized Metasequoia from Tokamachi and Kumagaya sites.
Fossilized Metasequoia branchlet and needles from Tokamachi (a) and Kumagaya (b) as examples to show the megafossils of Metasequoia used in this research, compare with a modern Metasequoia branchlet (c). White arrows in (a) indicate the branchlet.
Fig 2.
Localities where fossilized Metasequoia were obtained.
Locality map (a) showing the seven fossil sites in China and Japan. Enlarged map (b) illustrating the central area of Japan showing the position of the six localities in Japan: Kumagaya, Sennan, Konan, Hachioji, Tokamachi and Ikoma. Different colors identify the different ages of the localities (Red: Miocene; Green: Pliocene; Blue: Pleistocene).
Table 1.
Metasequoia samples used for reconstructing paleo-CO2 including fossil sites, ages, latitude, and longitude.
Table 2.
Sample size of localities.
Fig 3.
Lower cuticles of the Metasequoia needle samples from different localities.
Lower cuticles of Metasequoia needles from a: Sanzhangtian; b: Ikoma; c: Kumagaya; d: Tokamachi; e: Konan; f: Sennan; and g: Hachioji. (Scale Bar = 100μm)
Table 3.
Fossilized Metasequoia stomatal index and paleo-[CO2]atm concentration estimates during Cenozoic.
Table 4.
Mean difference of the least significant different (LSD) on stomatal index of fossil localities.
Fig 4.
Trend of paleo-[CO2]atm during late Cenozoic.
(a) Deep-sea temperatures estimated from δ18O since 20 Ma [46]; (b) atmospheric CO2 reconstructed from terrestrial and marine proxies following recent revisions (S2 Table). Vertical error bars: standard deviation of paleo-[CO2]atm values, and horizontal error bars: standard deviation of materials’ age. The current atmospheric CO2 concentration (390 ppmv) is indicated by the horizontal dashed line.
Fig 5.
Reconstructed paleo-[CO2]atm of Pliocene to Pleistocene compared with reconstructed paleo-temperature and benthic δ18O record.
(a) Reconstructed paleo-[CO2]atm based on terrestrial and marine proxies following recent revisions (S2 Table) along with our data. Vertical error bars: standard deviation of paleo-[CO2]atm values, and horizontal error bars: standard deviation of ages of materials. The current atmospheric CO2 concentration (390 ppmv) is indicated by the horizontal dashed line. (b) SST records for the last 3.5 Ma from southern South China Sea [56]. (c) Global oxygen isotopes of benthic foraminifera shells [57]. The vertical color bands in (a), (b), and (c) indicate the periods considered by this research, and same period is marked by the same color.