Last glacial sea-level change deduced from uplifted coral terraces of Huon Peninsula, Papua New Guinea

We have dated corals sampled from the uplifted terraces of Huon Peninsula, Papua New Guinea, that grew during the Marine Isotope Stage 3, to reconstruct sea-levels of the last glacial period from 30 to 55 ka (kiloannum). Mass spectrometric U-series dating methods resulted in high precision dates and could also be used to recognize diagenetically altered samples. The only quantitative test of open-system behaviour of both uranium and thorium isotopes involves the comparison of ²³⁴U/²³⁸U ratios, at the time of coral growth, with present sea-water values. Additional tests included checks for systematic variations in stable isotopes, X-ray diffraction to detect calcification and petrographic examination. Sea-levels were corrected for glacio-hydro-isostatic variations and also for the depth range of coral growth habitat. Sea-levels from 30 to 55 ka were approximately 80 m lower than present. Superimposed on this general trend, four periodic sea-level high-stands were found, at 6-8 ka intervals, approximately at 30, 38, 44 and 52 ka, that appear to be synchronous with rapid climate variations previously observed in ice cores and in deep sea sediments.