Oxygen and carbon isotopes of Cibicides wuellerstorfi, Cibicides kullenbergi and Globigerinoides sacculifer at DSDP Holes 72-516A and 72-517

The d18O records of Cibicides wuellerstorfi and Globigerinoides sacculifer do not vary in phase with one another, indicating that the d18O of C. wuellerstorfi is reflecting changing glacial ice volumes, but the d18O of G. sacculifer is being influenced more by other factors, such as variable sea-surface temperatures and salinities.

A net depletion in 18O and a series of very low-amplitude fluctuations characterize the late Pliocene planktonic d18O record. The stability of this section may be related to increasing surface-water temperatures in middle southern latitudes during northern hemisphere glacial ice buildup caused by differences in the phasing of the orbital precessional cycle between the northern and southern hemispheres. Hole 516A is presently located in an area of strong d13C gradients in the water column, and a similar situation probably prevailed during the Pliocene.