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
Final Report Abstract
Answers to all the the initially posed questions addressed in the proposal could be found. Whereas postglacial sea-level rise was of paramount significance, subsidence apparently played only a minor role in creating accommodation space for both barrier and fringing reef accretion. Holocene barrier and fringing reefs exhibit aggradational and retrogradational and subsequent progradational architectures that were largely controlled by sea-level variation. Holocene fringing and barrier reefs have been forming more or less contemporaneously during the Holocene. Interestingly, fringing reefs grew in somewhat shallower water than the barrier reef during the early-mid Holocene. The Holocene barrier reef grew on a Pleistocene barrier reef antecedent topography. On the windward island side, a Pleistocene fringing reef formed the pedestal of the Holocene fringing reef. The history of the rare lagoonal patch reefs ion Bora Bora could not be deciphered, however, a comparatively young / late Holocene reef origin is likely. Microbialites are a major element of the early-mid Holocene reef framework. Preliminary organic geochemical data suggest sulfate-reducing bacteria as significant triggers of microbial carbonate formation, similar to other examples (Heindel et al. 2012). Microbialites presumably accreted in shallow reef cavities during comparatively rapid rise of sea level and ceased forming in the late Holocene. Lagoonal infill of the barrier-reef system is characterized by early-mid Holocene background sedimentation as well as siliciclastic and organic input from the central volcanic island. The latter has been especially high during initial marine inundation. Interestingly, siderite has been forming during this phase. Pure carbonate sedimentation and deepening upward predominate during the mid-late Holocene. Lateral infill from marginal lagoon parts resumes in the mid-Holocene and has been creating wide sand aprons. Non-skeletal carbonate production apparently started only in the latest Holocene (last ca. 1 kyr) in intermediate depths at marginal sand apron positions. We had not expected that the Holocene thickness at the barrier reef margin would reach and in places even exceed 30 m. This fact changed the schedule during the first expedition, and resulted in a lower number of core holes than initially planned. Frankfurter Rundschau, Friday, 11 December 2015, page 28: "Darwin auf dem Prüfstand - Geologen untersuchen in der Südsee die Theorie zur Entstehung von Korallenriffen" has reported on this project.
Publications
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(2019) Holocene and Pleistocene fringing reef growth and the role of accommodation space and exposure to waves and currents (Bora Bora, Society Islands, French Polynesia). Sedimentology 66 (1) 305–328
Gischler, Eberhard; Hudson, J. Harold; Humblet, Marc; Braga, Juan Carlos; Schmitt, Dominik; Isaack, Anja; Eisenhauer, Anton; Camoin, Gilbert F.
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(2014): First results of an expedition to Bora Bora, Darwin's type barrier reef (Society Islands, Pacific): the influence of sea level, antecedent topography, and subsidence on reef development. IAS International Meeting Geneva
Gischler, E., Isaack, A., Hudson, J.H., Camoin, G., Anselmetti, F.A.
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(2015): Holocene sedimentation in the barrier reef lagoon of Bora Bora, Society Islands (French Polynesia), south Pacific. Annual meeting of the German geological societies, Berlin [Price as best young-scientist presentation]
Isaack, A., Gischler, E., Hudson, H., Anselmetti, F., Lohner, A., Camoin, G.
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(2015): Late Quaternary development of barrier and fringing reefs of Bora Bora, Society Islands, South Pacific: the influence of subsidence, sea level, and antecedent topography. IAS Meeting Krakow
Gischler, E., Isaack, A., Hudson, H., Anselmetti, F., Humblet, M., Eisenhauer, A., Camoin, G.
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(2015): Late Quaternary reef response to sea level and subsidence in Bora Bora, Society Islands, south Pacific (French Polynesia). Annual meeting of the German geological societies, Berlin
Gischler, E., Isaack, A., Hudson, H., Anselmetti, F., Humblet, M., Braga, J.C., Eisenhauer, A., Camoin, G.
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(2016) Late Quaternary barrier and fringing reef development of Bora Bora (Society Islands, south Pacific): first subsurface data from the Darwin type barrier-reef system. Sedimentology, 63: 1522-1549
Gischler, E., Hudson, J.H., Humblet, M., Braga, J.C., Eisenhauer, A., Isaack, A., Anselmetti, F.S., Camoin, G.F.
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(2016): A new model evaluating sediment dynamics throughout the Holocene: insights from a mixed carbonate-siliciclastic lagoon (Bora Bora, Society Islands, French Polynesia, South Pacific). Sedimentary Geology, 343: 99-118
Isaack, A., Gischler, E., Hudson, J.H., Anselmetti, F.A., Lohner, A., Garbode, E., Camoin, G.
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(2016): Mid-to-late Holocene sediment dynamics and driving mechanisms in a mixed carbonate-siliciclastic lagoon (Bora Bora, French Polynesia, South Pacific). International Coral Reef Symposium Hawaii
Isaack, A., Gischler, E., Hudson, J.H., Anselmetti, F.A., Lohner, A., Garbode, E., Camoin, G.
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(2016): Rising sea level and reef response in Bora Bora, Society Islands, South Pacific (French Polynesia). International Coral Reef Symposium Hawaii
Gischler, E., Hudson, J.H., Humblet, M., Braga, J.C., Eisenhauer, A., Isaack, A., Anselmetti, F.A., Camoin, G.
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(2017): Facies variations in the mixed carbonate-siliciclastic lagoon of Bora Bora, French Polynesia: the influence of Holocene sea-level and climate change in the South Pacific. Marine Geology, 390: 1-22
Isaack, A., Gischler, E., Hudson, J.H., Anselmetti, F.S., Buhre, S., Camoin, G.F.
