Miocene benthic foraminifer oxygen and carbon isotope record of ODP Site 115-709

The benthic isotopic record of Miocene Cibicidoides from Site 709 provides a record of conditions in the Indian Ocean at a depth of about 3200 mbsf. As expected, the record qualitatively resembles those of other Deep Sea Drilling Project and Ocean Drilling Program sites. The data are consistent with the scenario for the evolution of thermohaline circulation in the Miocene Indian Ocean proposed by Woodruff and Savin (1989, doi:10.1029/PA004i001p00087). Further testing of that scenario, however, requires isotopic data for Cibicidoides from other Indian Ocean sites. There is a correlation between d13C values of Cibicidoides and planktonic:benthic (P:B)ratios of Site 709 sediments, implying a causal relationship between the corrosiveness of deep waters and concentration of CO2 derived from oxidation of organic matter.