Time scales and modes of reef lagoon infilling in the Maldives and controls on the onset of reef island formation

Perry, C.T., Kench, P.S., Smithers, S.G., Yamano, H., O'Leary, M., and Gulliver, Pauline (2013) Time scales and modes of reef lagoon infilling in the Maldives and controls on the onset of reef island formation. Geology, 41 (10). pp. 1111-1114.

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Abstract

Faro are annular reefs, with reef flats near sea level and lagoons of variable depth, characteristic of both the perimeter and lagoons of Maldivian (Indian Ocean) atolls. Their geo-morphic development remains largely unknown, but where faro lagoons (termed velu in Maldivian) have infilled and support reef islands, these provide precious habitable land. Understanding the timing and modes of velu infilling is thus directly relevant to questions about reef island development and vulnerability. Here we use a chronostratigraphic data set obtained from a range of atoll-interior faro with partially to fully filled velu (including those with reef islands) from Baa (South Maalhosmadulu) Atoll, Maldives, to determine time scales and modes of velu infilling, and to identify the temporal and spatial thresholds that control reef island formation. Our data suggest a systematic relationship between faro size, velu infilling, and island development. These relationships likely vary between atolls as a function of atoll lagoon depth, but in Baa Atoll, our data set indicates the following faro-size relationships exist: (1) faros <similar to 0.5 km² have velu that were completely infilled by ca. 3000 calibrated years B. P. (cal yr B. P.) with islands having established on these deposits by ca. 2.5 cal kyr B. P.; (2) faros >0.5 km² but <similar to 1.25 km² have velu in late stages of infill, may support unvegetated sand cays and, given sufficient sand supply, may evolve into larger, more permanent islands; and (3) faros >similar to 1.25 km² have unfilled (deeper) velu which might only infill over long time scales and which are thus unlikely to support new island initiation. These new observations, when combined with previously published data on Maldivian reef island development, suggest that while the velu of the largest faro are unlikely to fill over the next few centuries (at least), other faro with near-infilled velu may provide important foci for future reef-island building, even under present highstand (and slightly rising) sea levels.

Item ID: 31662
Item Type: Article (Refereed Research - C1)
Keywords: holocene reef growth; carbonate sedimentation; atoll; Indian Ocean
Additional Information:

© 2013 Geological Society of America. Gold Open Access: This paper is published under the CC-BY license.

ISSN: 1943-2682
Funders: International Association of Geomorphologists REEForm Working Group, Natural Environment Research Council (UK)
Projects and Grants: REEForm contribution number RF-012, NERC radiocarbon dating allocation 1580.0911
Date Deposited: 26 Feb 2014 09:37
FoR Codes: 04 EARTH SCIENCES > 0406 Physical Geography and Environmental Geoscience > 040699 Physical Geography and Environmental Geoscience not elsewhere classified @ 40%
04 EARTH SCIENCES > 0406 Physical Geography and Environmental Geoscience > 040606 Quaternary Environments @ 30%
04 EARTH SCIENCES > 0406 Physical Geography and Environmental Geoscience > 040601 Geomorphology and Regolith and Landscape Evolution @ 30%
SEO Codes: 96 ENVIRONMENT > 9605 Ecosystem Assessment and Management > 960503 Ecosystem Assessment and Management of Coastal and Estuarine Environments @ 100%
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