Postglacial growth history of a French Polynesian barrier reef tract, Tahiti, central Pacific

The internal structure and growth pattern of Tahiti reefs over the last 14 ka is reconstructed using sedimentological, morphological and palaeobiologi cal data coupled with radiometric dates in drill cores through the modern b arrier reef. Flooding of the volcaniclastic deposits or the karst surface o f a Pleistocene reef started at approximate to 14 ka BP, and coral growth b egan shortly after inundation. The sequence in the Tahiti barrier-reef edge has formed predominantly through long-term keep-up growth controlled by st able environmental conditions, while the adjacent backreef deposits did not start to accumulate before sea-level stabilization, around 6 ka. The domin ance of Porites communities and the coeval occurrence of branching gracile Lithophyllum in the lowermost part of the postglacial reef sequence (14-11 ka) suggest the prevalence of uniformly moderate- to low-energy conditions and/or growth in slightly deeper waters all over the drilled area during th e early reef stages. During the last 11 ka, the reef frameworks developed i n a high-energy environment, at maximum water depths of 5-6 m, and were dom inated by an Acropora robusta/danai-Hydrolithon onkodes association; the lo cal interlayering of other coralgal assemblages (dominated by tabular Acrop ora or domal Porites) reflects distinct diversification stages, resulting e ither from the palaeotopographic control of the substrate or from slight an d episodic environmental changes.