Postglacial fringing-reef to barrier-reef conversion on Tahiti links Darwin's reef types.
In 1842 Charles Darwin claimed that vertical growth on a subsiding foundation caused fringing reefs to transform into barrier reefs then atolls. Yet historically no transition between reef types has been discovered and they are widely considered to develop independently from antecedent foundations during glacio-eustatic sea-level rise. Here we reconstruct reef development from cores recovered by IODP Expedition 310 to Tahiti, and show that a fringing reef retreated upslope during postglacial sea-level rise and transformed into a barrier reef when it encountered a Pleistocene reef-flat platform. The reef became stranded on the platform edge, creating a lagoon that isolated it from coastal sediment and facilitated a switch to a faster-growing coral assemblage dominated by acroporids. The switch increased the reef's accretion rate, allowing it to keep pace with rising sea level, and transform into a barrier reef. This retreat mechanism not only links Darwin's reef types, but explains the re-occupation of reefs during Pleistocene glacio-eustacy.
Unidad de Sistemas Arrecifales (Puerto Morelos), Instituto de Ciencias del Mar y Limnologia, Universidad Nacional Autonoma de México, A.P. 1152, Cancun, Quintana Roo, C.P. 77500, Mexico.
Paul
P
Blanchon
Unidad de Sistemas Arrecifales (Puerto Morelos), Posgrado en Ciencias del Mar y Limnologia, Universidad Nacional Autonoma de México, A.P. 1152, Cancun, Quintana Roo, C.P. 77500, Mexico.
Marian
M
Granados-Corea
School of Geosciences, University of Sydney, NSW 2006, Australia.
Elizabeth
E
Abbey
Departamento de Estratigrafia y Paleontologia, Universidad de Granada, Campus Fuentenueva, 18002 Granada, Spain.
Juan C
JC
Braga
School of Geographical and Earth Sciences, University of Glasgow, Glasgow G12 8QQ, UK.
Colin
C
Braithwaite
Department of Resource Management and Geography, The University of Melbourne, Parkville Vic 3010, Australia.
David M
DM
Kennedy
Cambridge Coastal Research Unit, Department of Geography, University of Cambridge, Downing Place, Cambridge CB2 3EN, UK.
Tom
T
Spencer
Geocoastal Research Group, School of Geosciences, The University of Sydney, NSW 2006, Australia.
Jody M
JM
Webster
School of Earth and Environmental Sciences, University of Wollongong, NSW 2522, Australia.
Colin D
CD
Woodroffe