Carbonate Dissolution Fluctuations in the Western Equatorial Pacific During the Late Quaternary

Planktonic foraminiferal test fragmentation in three cores along a depth transect from the western equatorial Pacific (ERDC‐93P, 1619 m; RC17‐177, 2600 m; V28‐238, 3120 m Thompson, 1976) were examined for the last 500 kyr at sample intervals from 2.5 to 5 kyr to study the fluctuations of dissolution in the western equatorial Pacific. The age models were constructed by correlating the δ 18 O records with the SPECMAP stack Imbrie et al., 1984. Results showed that intermediate and deep waters experienced the same patterns of dissolution through climatic cycles. Fragmentation varied with a greater amplitude, and the carbonate ion concentration changed less, in the deep than in the intermediate water. Dissolution has significant variance distributions and coherencies with δ 18 O over the 100, 41, and 23 kyr periods of orbital variations; dissolution maxima lag ice volume minima by 6 to 20 kyr. The dissolution variability was consistent with recent geochemical models which seek to explain the reduction of atmospheric CO 2 concentration at the last glacial maximum Broecker, 1982; Boyle, 1988.