B/Ca ratios of benthic foraminifera

We present modern B/Ca core-top calibrations for the epifaunal benthic foraminifer Nuttallides umbonifera and the infaunal Oridorsalis umbonatus to test whether B/Ca values in these species can be used for the reconstruction of paleo-D[[CO3]2-]. O. umbonatus originated in the Late Cretaceous and remains extant, whereas N. umbonifera originated in the Eocene and is the closest extant relative to Nuttallides truempyi, which ranges from the Late Cretaceous through the Eocene. We measured B/Ca in both species in 35 Holocene sediment samples from the Atlantic, Pacific and Southern Oceans. B/Ca values in epifaunal N. umbonifera (~ 85-175 µmol/mol) are consistently lower than values reported for epifaunal Cibicidoides (Cibicides) wuellerstorfi (130-250 µmol/mol), though the sensitivity of D[[CO3]2-] on B/Ca in N. umbonifera (1.23 ± 0.15) is similar to that in C. wuellerstorfi (1.14 ± 0.048). In addition, we show that B/Ca values of paired N. umbonifera and its extinct ancestor, N. truempyi, from Eocene cores are indistinguishable within error. In contrast, both the B/Ca (35-85 µmol/mol) and sensitivity to D[[CO3]2-] (0.29 ± 0.20) of core-top O. umbonatus are considerably lower (as in other infaunal species), and this offset extends into the Paleocene. Thus the B/Ca of N. umbonifera and its ancestor can be used to reconstruct bottom water D[[CO3]2?], whereas O. umbonatus B/Ca appears to be buffered by porewater [[CO3]2-] and suited for constraining long-term drift in seawater B/Ca.

(Table, Appendix C) Metal content of nodules at Sea Scope stations based upon XRF analyses at the Ore Microscopy Laboratory, Washington State Unicersity, USA

New information on possible resource value of sea floor manganese nodule deposits in the eastern north Pacific has been obtained by a study of records and collections of the 1972 Sea Scope Expedition. Nodule abundance (percent of sea floor covered) varies greatly, according to photographs from eight stations and data from other sources. All estimates considered reliable are plotted on a map of the region. Similar maps show the average content of Ni, Cu, Mn and Co at 89 stations from which three or more nodules were analyzed. Variations in nodule metal content at each station are shown graphically in an appendix, where data on nodule sizes are also given. Results of new analyses of 420 nodules from 93 stations for mn, fe, ni, cu, CO, and zn are listed in another appendix. Relatively high Ni + Cu content is restricted chiefly to four groups of stations in the equatorial region, where group averages are 1.86, 1.99, 2.47, and 2.55 weight-percent. Prepared for United States Department of the Interior, Bureau of Mines. Grant no. GO284008-02-MAS. - NTIS PB82-142571.