A preliminary study of the distribution, sizes and orientations of large reef-top coral boulders deposited by extreme waves at Makemo Atoll, French Polynesia A preliminary study of the distribution, sizes and orientations of large reef-top coral boulders deposited by extreme waves at Makemo Atoll, French Polynesia
Résumé
The history of extreme wave events on the Tuamotu Archipelago of French Polynesia in the central South Pacific remains poorly understood, even though huge wave deposited coastal boulders were identified in the area decades ago. Numerous large coral boulders deposited on the reef flats of Makemo Atoll (16.56°S, 143.73°W) were investigated in this study in an attempt to understand the characteristics of extreme wave events in the region. The positions, dimensions and orientations of 286 boulders were measured along over 15 km of the northern coastline of the atoll. The biggest clast measures over 130 m 3 in size and it weighs more than 310 tonnes. The size-distribution of the Makemo boulders suggests that these huge clasts were transported by extreme storm waves. The long-axes of boulders are mostly aligned parallel to sub-parallel to the shoreline. However, a relationship between the boulder size and orientation was not found, suggesting the orientation of boulders is not representative of boulder transport mode.