Holocene Depositional History of Low-Lying Reef-Rim Carbonate Islets of Fakarava Atoll, Northwest Tuamotu, Central South Pacific

Author:

Montaggioni Lucien F.1,Salvat Bernard2,Pons-Branchu Edwige3,Martin-Garin Bertrand1ORCID,Dapoigny Arnaud3,Brunaud Éric4,Poli Gilbert5,Tatarata Miri6

Affiliation:

1. Aix Marseille Univ, CNRS, IRD, INRAE, CEREGE, 13331 Marseille, France

2. PSL-École Pratique des Hautes Études, UAR 3278, EPHE, CNRS, UPVD, Criobe, Labex Corail, Université de Perpignan, 66860 Perpignan, France

3. LSCE–IPSL, CEA, CNRS, UVSQ, Université Paris-Saclay, 91198 Gif-sur-Yvette, France

4. Independent Researcher, 44470 Carquefou, France

5. Independent Researcher, 75016 Paris, France

6. Délégation à l’Environnement, 98713 Papeete, Tahiti, French Polynesia

Abstract

Assumptions about the fate of low-lying coral reef islands (atolls) facing global warming are poorly constrained, due to insufficient information on their depositional history. Based on the U/Th dating of 48 coral clasts, the chronostratigraphic analysis of excavated sections through rim islets (motu) at the windward and leeward sides of Fakarava Atoll (Tuamotu, French Polynesia) reveal that the deposition of coral detritus started approximately 2000 years ago. Most of these deposits lie on conglomerate pavements or reef flat surfaces, and are about 4500 to 3000 years old. The islet expansion at the windward sites seems to have operated coevally across the reef rim, from the ocean-facing shore lagoonwards. Meanwhile, well-developed, continuous, elongated, vegetated islets mostly occur along the windward, northeast to southeast coast, and isolated islets, vegetated or not, associated with the dense networks of conglomerates, are common on the leeward, partly submerged, western rim. Islet accretion on the windward rim sides is believed to have been mainly triggered by winter storms and occasional cyclonic events, whilst the leeward atoll parts were most likely shaped by distant-source swells from mid to high latitudes. The projections of the accelerated sea level rise in the future suggest that the long-term islet stability at Fakarava could be altered because the islets have accreted under the conditions of the falling sea level.

Publisher

MDPI AG

Subject

General Earth and Planetary Sciences

Reference108 articles.

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