Stable carbon and oxygen isotope ratios of planktonic and benthic foraminifera of ODP Hole 115-714B (Table 1)

Combined data on benthic foraminifers, siliceous fossils, and stable isotopes depict times of enhanced organic carbon oxidation in the sediments and high primary productivity in the southern Indian upwelling zone during the Miocene. Increased abundance of the diatom productivity index, the Thalassionema group, elevated diatom and uvigerinid abundances, and bolivinid diversity all suggest heightened primary productivity and the development of a mid-depth oxygen minimum between ~17 and 10 Ma.
The abundance of bolivinids with large pores and crenulate chamber surfaces may indicate more aerated pore waters in the upper few centimeters of the partly siliceous sediments deposited during the episode of higher primary productivity and increased organic carbon flux around 10 Ma.