The chronological framework of the upper 837.11-m composite section (~32.7 Ma to present) at Sites 1147 and 1148 is based on biostratigraphy and magnetostratigraphy (Wang, Prell, Blum, et al., 2000; Z. Jian et al., unpubl. data). The isotope records below 476.68 mcd (~26.5–32.7 Ma) cannot be used as a paleoclimatic indicator because all the calcareous microfossils were heavily mineralized (Zhao et al., 2001a) as a result of diagenesis. However, oxygen and carbon isotope measurements from the upper 476.68 mcd (Fig. F1) are considered to reflect paleoceanographic changes in the northern South China Sea since ~26.5 Ma (Fig. F2). The oxygen isotope record of benthic foraminifers can be divided into three major intervals: 0–3.2, 3.2–13.6, and 13.6–26.5 Ma (Fig. F2). Its steplike variation indicates a general cooling trend for the past 26.5 m.y., which is most obvious since 3.2 Ma (Figs. F2, F3). The steplike cooling may be equivalent to major ice sheet expansions, as mentioned by Lear et al. (2000). Both benthic and planktonic 
13C display a generally decreasing trend (Zhao et al., 2001b) with obvious increases in 13C at 24.4–22.7 and 17.9–16.0 Ma, the latter case marking the "Monterey carbon positive excursion." The planktonic foraminifer 18O record significantly differs from the benthic record, possibly indicating regional changes in sea-surface temperature and/or salinity during the Neogene.
