Core Top 14C Ages as a Function of Latitude and Water Depth on the Ontong‐Java Plateau

Radiocarbon measurements on core tops from the Ontong‐Java plateau confirm a previous finding by Berger and Killingley 1982 that at any given water depth, cores taken on the equator have higher accumulation rates and younger core top ages than their off‐equator counterparts. Further, these new results fortify the conclusion by Broecker et al. 1991 that the increase in core top radiocarbon age with water depth rules out homogeneous dissolution within the pore waters as the dominant mechanism. Either most of the dissolution must occur prior to burial or it must occur during the first pass through the respiration‐CO 2 ‐rich upper pore waters after which the calcite grains become armored against further dissolution. A puzzling aspect of this new data set is that despite the sizable difference in accumulation rate, the extent of dissolution as measured by either the CaCO 3 content or the ratio of CaCO 3 in the >150‐µm size fraction to that in the < 63‐µm fraction is no different off than on the equator. In order to reconcile the results of this study with those obtained by Hales and Emerson 1996 using in situ electrodes, it is necessary to call upon calcite armoring.