Recollecting and Drilling Emerged Coral Reefs on the Huon Peninsula, Papua New Guinea

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Reef terraces on the Huon Peninsula of Papua New Guinea were the basis of a series of studies beginning in the early 1970's that gave impetus to the use of coral reefs to date ice ages. The tectonic uplift rate on the Huon Peninsula is so rapid (1 to 4 mm/yr) that many of the lesser fluctuations of sea level within the last ice age are recorded by small, partly overlapping reefs. This project represents major recollecting effort in collaboration with Australian scientists and a group of international experts, because few samples are now available from the Huon terraces. Also, drill cores through the youngest, Holocene, reef and a selected set of older reefs will define the rate and amplitude of sea-level changes and climatic fluctuations during the last ice age. Newly developed analytical techniques of mass-spectrometric Uranium-series dating and electron spin resonance (ESR) dating offer unprecedented precision and a longer time range for dating emerged coral reefs on uplifting tropical coasts. Unweathered, fresh coral samples are essential to both techniques. Coral-reef growth is closely controlled by sea-level fluctuations, which in turn are governed by the expansion and shrinkage of continental ice sheets. Thus, precise dates on corals from the Huon Peninsula, comparable to recently published mass-spectrometer Uranium-series ages in the range of 125,700 + 1200 years for corals from Barbados, will open a new era of precision for dating ice ages and their concomitant changes in sea levels. The new methods will permit a rigorous test of the Milankovitch theory of ice ages and more accurate comparison with the deep-sea isotope record.