Reef coralgal assemblages as recorders of paleobathymetry and sea level changes in the Indo-Pacific province

The coralgal framework within the outer reef margin of many Indo-Pacific re efs exhibits three main shallow-water communities, the environmental signif icance of which can be inferred by comparison with their modern counterpart s. A community dominated by tabular Acropora gr. hyacinthus/cytherea with b ranching Pocillopora damicornis, P. eydouxi, Montipora digitata: occasional domal faviids and mm-thick crusts of the coralline algae Lithophyllum and Mesophyllum (mainly), typical of the 6 - 15 m paleodepth range; a community including robust-branching Acropora gr. danai/robusta, A. humilis, A. digi tifera and subordinate Favia stelligera, Echinopora gemmacea, associated to vermetid gastropods and thick coralline crusts of Hydrolithon cf. onkodes and Neogoniolithon cf. fosliei flourishing in depths less than 6 m; in medi um-to-high water-energy settings, a community composed of domal Porites cf. lutea and P. cf. lobata with occasional Acropora gr. danai/robusta and cm- thick crusts of coralline algae in sheltered habitats in depths less than 1 0 m. These biological assemblages allow us to determine relationships between re ef growth and paleobathymetry and, consequently, to reconstruct regional re lative sea-level curves. High water-energy reefal assemblages provide stron ger evidence for reconstructing sea-level curves than low-energy buildups, because they have generally been controlled by a keep-up growth mode. Subsi ding reef sites seem to be more reliable indicators of sea-level Variations because they usually present expanded reef sequences. (C) 1999 Elsevier Sc ience Ltd. All rights reserved.