A Cenozoic Record of Deep Oceanic Zn Isotopic Composition in Ferromanganese Crusts

The zinc (Zn) isotopic composition (δ 66 Zn) of the deep ocean (>1000 m) can provide insights into the carbon cycle, the biological pump, and hydrothermal activity. However, we have an incomplete view of the temporal and spatial evolution of deep-ocean Zn isotopes. Here, we present new δ 66 Zn values of Fe-Mn crusts from the Pacific Ocean, which we used to reconstruct the evolution of deep-ocean δ 66 Zn for the Cenozoic. Our results suggest that the δ 66 Zn values remain stable in the deep Pacific Ocean at around ~ 0.5‰ through the Cenozoic. Our results limit the extent of change in organic zinc burial through the Cenozoic. However, given uncertainties in the global mass balance and analytical error, variations of roughly 20% in organic zinc burial are still possible.