Stable isotope ratios of benthic and planktonic foraminifera from Late Miocene sediments of DSDP Hole 24-238 on the Central Indian Ocean Ridge (Appendix 1)

All species analyzed in the Late Miocene section of DSDP Site 238 show a shift towards lighter values of delta13C by about 0.8‰. The oxygen isotope signal indicates that the pre-shift period is climatically quiet while the post-shift period has strong fluctuations.

We suggest that the shift reflects a sudden increase in the rate of supply of organic carbon from coastal lowlands and from shelves exposed by regression, as well as a change in deep circulation patterns and ocean fertility. The event marks the transition of the ocean-atmosphere system from a quiet Early and Middle Neogene climatic regime toward a Late Neogene regime characterized by climatic amplifying mechanisms (albedo feedback, bottom water production) located around the northern North Atlantic.