CONCLUSIONS

Multiple interpretations are possible for this long but low-resolution alkenone record. In general, this record provides marine evidence in support of other climate indicators for global-scale Neogene cooling and for the history of monsoon development during the last 35 m.y. This includes vegetation shifts on land (wet to arid) as well as increases in foraminifer abundance due to upwelling and increases in ¹³C and ¹⁸O values due to a shift toward seasonality (Raymo et al., 1988; Ruddiman and Kutzbach, 1989; Kroon et al., 1991; Cerling, 1997; Ma et al., 1998; Shipboard Scientific Party, 2000). After the collision of India with the Asian continent and during the initial opening of the SCS Basin (before ~31 Ma), alkenones were not detected because of either the lack of production or lack of alkenone-producing species in the SCS. Between ~8 and 31 Ma, only C_37:2 was detected, which most likely indicates warmer SST (>28°C) or a period of time where temperature control on alkenone unsaturation was evolving. Finally, between 0 and 8 Ma, both C_37:2 and C_37:3 were detected, which produces an U^k´₃₇ index from 0 to 2.5 Ma with SST within the range of previously determined glacial–interglacial values. These results suggest that the U^k´₃₇ method can serve as a potential long-term glacial–interglacial paleothermometer for the SCS, which can serve as a useful tool for understanding the development of the East Asian monsoon system, and that a high-resolution U^k´₃₇ record for at least the last 8 m.y. may be completed.