Oligocene strontium isotope stratigraphy of Indian Ocean sediments

Strontium isotope (87Sr/86Sr) ages have been established for Oligocene samples of Leg 119 Site 744, Leg 120 Sites 747 and 748, and Leg 121 Sites 756 and 757. Ages were determined using the strontium isotope age equation of Miller et al. (1988) and preliminary correlations have been made with available nannofossil biostratigraphy. The strontium isotope ages calculated here augment biostratigraphy, which for the Oligocene is characterized by long biozones, and provide additional detail where the paleomagnetic record is not clear (Sites 756 and 757). Results from the lower latitude Ninetyeast Ridge sites where standard calcareous nannofossil datums are present are compared to those of the higher latitude Kerguelen Plateau sites in order to examine biostratigraphic events across latitude in the Indian Ocean. The 87Sr/86Sr determined ages are used here as a tool for correlation.