Last ice age millennial scale climate changes recorded in Huon Peninsula corals

Uranium series and radiocarbon ages were measured in corals from the uplift ed coral terraces of Huon Peninsula (HP). Papua New Guinea, to provide a ca libration for the C-14 time scale beyond 30 ka (kilo annum). Improved analy tical procedures, and quantitative criteria fur sample selection, helped di scriminate diagenetically altered samples. The bass-line of the calibration curve follows the trend of increasing divergence from calendar ages, as es tablished by previous studies. Superimposed on this trend, four well-define d peaks of excess atmospheric radiocarbon were Found ranging in magnitude f rom 100% to 700%, relative to current levels. They are related to episodes of sea-level rise and reef growth at HP. These peaks appear to be synchrono us with Heinrich Events and concentrations of ice-rafted debris found in No rth Atlantic deep-sea cores. Relative timing of sea-level rise and atmosphe ric C-14 excess imply the following sequence of events: An initial sea-leve l high is followed by a large increase in atmospheric C-14 as the sea-level subsides. Over about 1800 years, the atmospheric radiocarbon drops to belo w present ambient levels. This cycle bears a close resemblance to ice-calvi ng episodes of Dansgaard-Oesechger and Bond cycles and the slow-down or com plete interruption of the North Atlantic thermohaline circulation. The incr ease in the atmospheric C-14 levels are attributed to the cessation of the North Atlantic circulation.