Covariance Patterns of Foraminiferal dgr18O: An Evaluation of Pliocene Ice Volume Changes Near 3.2 Million Years Ago.
Oxygen isotope data for a Pliocene interval from 3.6 to 2.8 million years ago show a mean increase (0.5 per mil) of benthic delta(18)O at about 3.2 million years ago, whereas planktic delta(18)O does not increase. This lack of covariance indicates that the event at 3.2 million years did not result in a permanent increase in the ice budget of either the Northern or the Southern Hemisphere.
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