Holocene development of reefs and lagoons of Bora Bora, Darwin's type barrier reef (French Polynesia): the influence of sea level, antecedent topography, and subsidence

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This project focusses on the Holocene development of the south Pacific barrier reef system of Bora Bora, Society Islands, French Polynesia. Bora Bora is significant as it is one of the few true oceanic barrier reef systems. Ch. Darwin (1842) selected Bora Bora as type barrier reef in order to put forward his universally known subsidence theory of reef development, which genetically connects fringing, barrier, and atoll reefs based on subsidence and vertical reef accretion around a volcanic island, ignoring glacio-eustatic sea-level variation. However, no subsurface data from Bora Bora existed as yet. The project has five objectives, including (1) to elaborate the influence of sea level, antecedent topography, and subsidence on barrier reef development, (2) to evaluate the impact of the same factors on the formation of lagoonal fringing and sand apron reefs, (3) to detail the occurrence of microbialites in Holocene coralgal reefs, (4) to understand patterns of lagoonal sedimentation including the role of siliciclastics and possible event/storm deposition, and (5) to evaluate the nature of non-skeletal carbonate grain sedimentation. In the first project phase, data from the analysis of rotary cores taken in leeward barrier and fringing reefs, as well as vibracores and seismic data collected in the lagoon have been used to detail the late Quaternary history of this unique reef location. For the the second project phase, applied for here, it is planned to collect and analyze additional rotary cores from windward barrier and fringing reefs and lagoonal patch reefs. The analysis of existing lagoonal vibracores and the seismic dataset will be continued and completed.