Mid-late holocene accretional history of low-lying, coral-reef rim islets, South-Marutea Atoll, Tuamotu, central South Pacific: The key role of marine hazard events

South-Marutea Atoll is located at the south-eastern end of Tuamotu Archipelago, French Polynesia, central South Pacific. Understanding modalities islet building from low-lying atolls over mid to late Holocene, in relation sea-level changes and cycles marine hazard events, a prerequisite for better anticipate future geomorphic which islets will likely be faced next decades under global climate warming. Herein presented depositional history two selected atoll islets, based on chronostratigraphic analysis sedimentary, coral-dominated sequences six excavations. Identified as Motu Aramu Vainono, these are respectively north-north-east due south rim. Additional surficial sampling was conducted modern ocean-facing shingle ridges, north-north-west (Motu Oire), west Aranui) east Tekava) rim areas, order date latest ridge-emplacement stages. Oire Aranui sites, along leeward protected trade winds, Aramu, Vainono Tekava windward sides, directly exposed northeasterly southeasterly storm swells respectively. A total 88 coral clasts were collected U/Th dated. The excavated range between 2.50 m 0.90 thickness, outer sides lagoonwards. Five lithofacies, including subfacies, recognized texture biological composition: boulder-cobble-dominated, pebble-dominated – pebble-supported sand-supported subfacies foraminifera-rich, sand-dominated an organic-rich, pebble sand facies. These facies tend distributed ocean landwards according decreasing grain-size gradient. model atoll-island accretion emerges with frequency intensity events. foundations consist conglomerate platforms, locally up 1.0 thick, deposited about 5,000 1,000 yr BP. Islets began accrete While occurred continuously last years, there apparent non-depositional episode, 4,000 2,000 BP, interpreted caused by marked decreased enso-related cyclone activity. ridges all studied sites regularly reshaped during millennium. During major accretion-islet episodes irrespective course sea level, indicating that change not driver accretion. Periodical, high-energy events clearly appear key controls shaping. Shifts source areas further increasing intensity, but lower frequency, enhanced enso variability throughout 21st century, postulated expose Gambier island Group stronger, fewer disturbance when compared millennia.