Carbon and oxgyen isotopic disequilibria of recent deep-sea benthic foraminifera

The carbon and oxygen isotopic compositons of 149 samples of benthic foraminifera from deep-sea core tops indicate that none of the nine species studied secrete calcium carbonate in isotopic equilibrium with ambient bottom water. Uvigerina, Pyrgo murrhina, and Oridosalis tener are the closest to 18O equilibrium (with average deviations about -0.4 per thousand), while Planulina wuellerstorfi and P. murrhina are the closest to 13C equilibrium (with average deviations about -1 per thousand). P. wuellerstorfi shows the most systematic relationship between delta13C and bottom water apparent oxygen utilization. The intraspecific variabilites in delta18O and delta13C suggest that estimates of bottom water paleotemperatures can be made to a precision of +-0.70C, while estimates of past apparent oxygen utilization (AOU) can be made to +- 35 μmol/kg. Based on intraspecific comparisons of the Recent samples with fossils, no temporal changes in the degree of either 18O or 13C disequilibrium have been detected for Planulina wuellestrofi, Uvigerina, Oridorsails tener and Globocassidulina subglobosa. (Auth.)