ISOTOPE STAGE 11 SEA LEVEL IN THE NETHERLANDS ANTILLES

The history of sea level change during Marine Isotope Stage (MIS)11 is of interest because this period may be the best model for the future of a warm earth. Studies were done on the Netherlands Antillean islands of Curaçao and Bonaire. The islands have experienced uplift during the Quaternary. Using the relatively well-known MIS 5e sea level and the present elevation of the 5e intertidal notch gives an uplift rate. Assuming this rate of uplift since MIS 11 allows a reconstruction of MIS 11 sea level.A sample of Montastraea annularis from the base of the MIS 11 terrace gave a date of 412 ±14 ka (initial 234U /238U 1.151) confirming the MIS 11 age of the terrace. Unfortunately no fossil coral from the top of the MIS 11 terrace could be dated, all being severely calcified. A date on the 5e material of 123.65 ±0.35 ka (initial 234U /238U 1.145) confirms its position. The 5e notch is at present at an elevation of 10.5 masl. This gives an uplift rate of 0.036m/kyr if 5e sea level is assumed to be +6 masl. The structure of the stage 11 terrace indicates an early rise to a stable sea level (confirmed by dating), followed by a period of rapid sea level rise to the highest sea level of MIS11 (although not dateable by U-series, field studies suggest this to be MIS 11). Ocean core site 607 shows two stages, with stable sea level ~415 – 422 ka, and rising sea level ~407-415 ka. The present terrace edge represents what is left after MIS 5e cliff retreat. If it represents the middle of the stable stage at ~418 ka, uplift of 15 m has occured. The terrace edge is at a present elevation of 21 masl, indicating a stable sea level high stand of +6 masl for the early part of MIS 11. The intertidal notch represents the highest sea level position. The present elevation of the highest MIS 11 deposits (mainly sands with rare corals) is 36.5 m and the intertidal notch is 37 masl. If the sea level peak occurred at 410 – 415 ka, 14.8 m of uplift has occurred and the MIS11 sea level peaked at +22 m.