Abstract
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.
Highlights
In 1842 Charles Darwin claimed that vertical growth on a subsiding foundation caused fringing reefs to transform into barrier reefs atolls
We reconstruct reef development from cores recovered by Integrated Ocean Drilling Program (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
Both ideas predicted single episodes of vertical reef growth in response to relative sea level (SL) change (Supplementary Fig. S1 online). Drilling to test these hypotheses subsequently showed that atolls were not formed by uninterrupted accretion of a single reef unit, but by stacked units formed during SL highstands, separated by laterally extensive subaerial-erosion surfaces formed during lowstands[4]
Summary
In 1842 Charles Darwin claimed that vertical growth on a subsiding foundation caused fringing reefs to transform into barrier reefs atolls. The presumption of static SL during subsidence came into question following the discovery of the Pleistocene glaciations[2], and led Daly[3] to suggest that reef types were not genetically related, but formed independently from differential wave-erosion of volcanic platforms during glacially-lowered SL Both ideas predicted single episodes of vertical reef growth in response to relative SL change (Supplementary Fig. S1 online). The Huon data seemed to confirm that the link between reef types was more than just a ‘‘theoretic possibility’’, it was still unclear why fringing reefs should develop into barriers and not retreat upslope tracking SL rise[15] Their apparent formation on simple slopes implies that some process fixes their position during SL rise and causes them to accrete vertically
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
