Holocene Palaeo-Environmental changes, central to north Great Barrier Reef inner zone

Fringing reefs and storm ridges, from inner-shelf sites on the Great Barrier Reef between 14° and 20° S, are examined for Holocene sea-level and climatic changes. The sites all lie close to the line along which the sea level of 5500 yr B. P. is thought, on isostatic grounds, to have been + 1 m. Coral microatolls are used as indicators of former sea levels on fringing reefs. 45 radiocarbon results from 11 sites range between 360 and 5855 yr B. P., and their age/height distribution shows that sea level fell smoothly from + 1 m at 6000 yr B. P. to its present position. Confidence limits on the sea-level trend are ±0.2 m; and no evidence for secondary oscillations of sea level has been found. With reference to climate, coral shingle and shell storm-ridge sequences at 5 places (total of 8 traverses) were surveyed and dated. Results from the best sequence (Princess Charlotte Bay) show that the average recurrence interval of major ridge-building storms is about 80 yr. Statistics of the series of storm-ridge ages do not show any identifiable changes in frequency of ridge building over the last 4000 yr and perhaps 6000 yr. It is concluded that evidence for climatic changes in the northern Great Barrier Reef in the last 6000 yr has not yet been found. The direction of continuing studies is outlined.