New magnetobiostratigraphic chronology and paleoceanographic changes across the Oligocene-Miocene boundary at DSDP Site 516 (Rio Grande Rise, SW Atlantic)

What is it about?

Around 23 million years ago, Antarctica experienced a dramatic cooling event, its ice cover more than doubling over a relatively brief period. Using new magnetic and biological analyses of sediments sampled in 1980 the southern Atlantic, we have produced a revised, more accurate record of the local changes in ocean conditions before, during, and after this event. We found that the sedimentation rate increased continually for the million years leading up to the ice expansion. This sedimentation increase was related to increased plankton growth at the ocean surface, with the shells of dead plankton falling to the sea floor as sediment.

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Why is it important?

The plankton remove carbon dioxide from the atmosphere, and bury the carbon in sediments when they fall to the sea floor. The long-term increase in carbon burial seen in our study may have played an important part in the sudden Antarctic cooling which followed it. Investigating connections like this helps us to understand how Antarctica responds to changes in atmospheric carbon dioxide.

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