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FIGURE 6.50 Paleo-sea level, as reconstructed from dated corals (Acropora palmata) submerged off the coast of Barbados.The left curve shows the MC-dated record and the right curve the 230Th/234U-dated record (Bard et al., l990).The right-hand axis shows an estimate of the effect of sea-level change on the isotopic composition (8I80) of the world ocean (Fairbanks, 1990).

plateau" is probably related to the very changes that are of interest, involving shifts in ocean circulation and de-gassing of "old" carbon from the deep ocean (Section 3.2.1.5). Bard et al. (1990, 1996) calibrated the 14C record in this crucial interval by 230Th/234U dates on corals, so that the Fairbanks (1989) meltwater record can be "corrected" to calendar yr (Fig. 6.51). This then places the peak of mwp-IA and mwp-IB at 14,000 and 11,300 calendar yr B.P., respectively (i.e., -11,800 and -10,000 14C yr B.P.).

A somewhat different scenario is presented by Keigwin et al. (1991) who link evidence for NADW reduction at 14,500, 13,500, 12,000, and 10,500 14C yr B.P., with times of increased meltwater flux to the North Atlantic. The 14,500 yr B.P.

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