patterns of: Tringing in New Caledonia (southwest Pacific) barrier reefs

In New Caledonia, core data indicate that the fringing reefs grew during the last interglacial and the Holocene, while the barrier reefs developed during several high sea level stands of the Quaternary. These growth periods are archived in a 128-m-long core from ZZotAmedee, offshore of Noumea. Directly upon the peridotitic substrate (reached at 126.50 m), a basal unit comprising abundant rhodoliths, molluscs and rare corals is characteristic of the pioneer stage of barrier reef development. Above it, a severely calcitized unit contains corals, molluscs and abundant micritic levels: Then, a sequence punctuated by several minor discontinuities and by a downward increase in diagenetic alteration is found. At 47 m core depth, a unit, which is thought to be related to isotopic stages 7 and 9, contains thin beds of coralgal frameworks and muddy detritus. The 125 ka-old reef, from 14 to 37 m core deep, is predominantly composed of biocalcarenites and rare coral colonies. Finally, the Holocene reef is composed of sands and scarce coral buildups. Drilling results indicate that the distributional patterns of the 125-ka-old reef bodies around New Caledonia express an increasing tendency of island subsidence northward, southwestward and more markedly seaward, mainly controlled by isostatic readjustments and margin collapse. O 1999 Ifremer / CNRS / IRD / Editions scientifiques et medicales Elsevier SAS