Shell weights for Globigerina sacculifer, Pulleniatina obliquiloculata, and Neogloboquadrina dutertrei from cores raised from a depth of 4.36 km (at 2 degrees S, 140 degrees W) reveal large dissolution-related shifts at Termination I and at the marine isotope stage 5-4 boundary. These shifts suggest that the carbonate ion concentration at this depth was ~27 mol kg-1 higher during glacial time than during marine isotope stages 1 and 5 and that the boundaries separating these regimes were quite sharp (in other words, the dissolution chronology has a rectangular character). However, when compared to results for a much shallower core, there are disconcerting aspects to this data set. One is that the initial shell wall thickness may depend on growth conditions. Hence the estimates of paleocarbonate ion concentrations presented here remain tentative.