Carbonate percentage and burial flux data for the 1.2-0.6 Ma interval at Ceara Rise Sites 925, 928, and 929 indicate coherent, in-phase variations in carbonate burial, global ice volume (benthic ) and Atlantic deep circulation (benthic ). A time-dependent calcite dissolution model is used to explore the sedimentary signatures of this and other processes. The data and model results are best reconciled if the strong 100-k.y. and 41-k.y. Atlantic carbonate cycles are interpreted in terms of rapid dissolution response signatures related to reduced glacial North Atlantic Deep Water production and associated northward incursion of corrosive Antarctic Bottom Water.
Whereas these Atlantic sediments exhibit in-phase covariation between carbonate burial and deep circulation, Pacific and Indian Ocean carbonate records significantly lag glacial ice volume. Carbonate burial outside the Atlantic basin during glacial intervals is interpreted to be related to enhanced preservation resulting from the temporary increase in mean ocean alkalinity levels (due to Atlantic carbonate dissolution) and the associated 5- to 10-k.y. carbonate ion response time. Based on these results, deep Atlantic circulation changes appear to be the dominant process responsible for the observed Pacific and Indian Ocean glacial-interglacial carbonate deposition patterns.
1Shackleton, N.J., Curry, W.B., Richter, C., and Bralower, T.J. (Eds.), 1997. Proc. ODP, Sci. Results, 154: College Station, TX (Ocean Drilling Program).
2Lamont-Doherty Earth Observatory, Palisades, NY 10964 U.S.A.
3The University of Chicago, Chicago, IL 60637, U.S.A.
4Pomona College, Claremont, CA 91711-6339, U.S.A.