Late Holocene sea-level change and reef-island evolution in New Caledonia

In New Caledonia, numerous rays are distributed on platform reefs in the southwest lagoon behind the barrier reef. At Mba Island, a vegetated sand cay in this area, we examined Holocene sea-level change, and reef development and evolution. The late Holocene sea-level curve for the area was updated using newly found fossil microatolls. Component-specific dating of foraminifera tests in the island sediment provided reliable ages of island formation. Mba Island initially formed around similar to 4500 cal yr B.P., when sea level was similar to 1.1 m higher than at present. The island formed on the leeward side of the platform reef, where the base had been constructed of lagoon- and reef-derived sediment of the platform reef. Sea-level fall since 2800 cal yr B.P. has likely caused reef-flat emergence at low tide and created a suitable habitat for foraminifera. Such a transition in ecology due to sea-level fall has been observed in other Pacific reefs, suggesting that the interaction between reef-flat formation, sediment production and sea-level fall is one of the critical factors determining island development. (C) 2014 Elsevier B.V. All rights reserved.