CONCLUSIONS

We identified seven carbonate accumulation events in the middle and late Eocene and linked these events to global cooling. The events most probably mark periods of significant cooling in the high latitudes and may mark small glaciations that were reversed after 1–2 m.y. We have evidence that the largest of these events, CAE-3, was associated with elevated primary productivity and CaCO3 production, but that CaCO3 production was not necessarily highest at the Pacific equator. Instead, CaCO3 production seems to be stronger south of the equatorial region. We observed changes in the carbon cycle independent of the productivity signal, signifying large changes in the ocean carbon reservoir. The repetition of the CAEs implies geosystem feedbacks that prevented large-scale development of ice sheets prior to the Eocene/Oligocene boundary, when the feedback mechanism apparently failed. Better delineation of the middle and late Eocene will improve our understanding of these events, but shelf-basin fractionation cannot be the only cause of increased CaCO3 burial in the equatorial Pacific.

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