Thresholds for Cenozoic bipolar glaciation

The long-standing view of Earth|[rsquo]|s Cenozoic glacial history calls for the first continental-scale glaciation of Antarctica in the earliest Oligocene epoch (|[sim]|33.6 million years ago), followed by the onset of northern-hemispheric glacial cycles in the late Pliocene epoch, about 31 million years later. The pivotal early Oligocene event is characterized by a rapid shift of 1.5 parts per thousand in deep-sea benthic oxygen-isotope values (Oi-1) within a few hundred thousand years, reflecting a combination of terrestrial ice growth and deep-sea cooling.

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