New model of reef-island evolution; Maldives, Indian Ocean
New model of reef-island evolution; Maldives, Indian Ocean
Geology (Boulder) (February 2005) 33 (2): 145-148
- absolute age
- Anthozoa
- atolls
- C-14
- carbon
- Cenozoic
- chronology
- clastic sediments
- Cnidaria
- Coelenterata
- dates
- geomorphology
- Holocene
- Indian Ocean Islands
- Invertebrata
- islands
- isotopes
- landform evolution
- lithofacies
- Maldive Islands
- models
- morphology
- Quaternary
- radioactive isotopes
- reef builders
- reefs
- sand
- sea-level changes
- sediments
- shore features
- stability
- topography
A new model of reef-island evolution, based on detailed morphostratigraphic analysis and radiometric dating of three islands in South Maalhosmadulu Atoll, Maldives, is presented. Islands initially formed on a foundation of lagoonal sediments between 5500 and 4500 yr B.P. when the reef surface was as much as 2.5 m below modern sea level. Islands accumulated rapidly during the following 1500 yr, effectively reaching their current dimensions by 4000 yr B.P. Since then the high circum-island peripheral ridge has been subject to seasonal and longer-term shoreline changes, while the outer reef has grown upward, reducing the energy window and confining the islands. This new model has far-reaching implications for island stability during a period of global warming and raised sea level, which will partially reactivate the energy window, although it is not expected to inhibit upward reef growth or compromise island stability.
