Zinc concentrations in benthic foraminifera reflect seawater chemistry

We have measured Zn/Ca ratios in two taxa of Holocene-aged benthic foramini fera from throughout the world's oceans. Zn/Ca is controlled by bottom wate r dissolved Zn concentration and, like Cd/Ca and Ba/Ca, by bottom water sat uration state with respect to calcite. Measurements on "live-collected" for aminifera suggest that the saturation effect occurs during growth and is no t a postdepositional artifact. Zn/Ca could be a sensitive paleoceanographic tracer because deep water masses have characteristic Zn concentrations tha t increase about tenfold from the deep North Atlantic to the deep North Pac ific. In addition, since Zn/Ca responds to a different range of saturation states than Cd/Ca, the two may be used together to evaluate changes in deep water carbonate ion (CO32-) concentration.