Paper short abstract:

We present results on the development of the reef flat and island, as well as the reconstruction of late Holocene sea-level change, at Wale Island on Pukapuka Atoll in the northern Cook Islands. The major part of the island formed under stable or slightly rising sea levels before 2100 cal yr BP.

Paper long abstract:

We present results on the development of the reef flat and island, as well as the reconstruction of late Holocene sea-level change, at Wale Island on Pukapuka Atoll in the northern Cook Islands, based on excavation of the island and examination of fossil corals. The fossil in-situ corals (microatolls) indicated sea level reached its present position by 4600 cal yr BP. A slight (~30 cm) highstand was found at around 2100 cal yr BP, and possible fall occurred after then. The windward and leeward reef flats formed by ~4100 cal yr BP and ~1400 cal yr BP, respectively. The oldest age of the island was 5500 cal yr BP from the northeast, windward part of the island. The island appeared to expand both to the west and to the south, and the major part of the island established before 2100 cal yr BP. The western (leeward) part of the island showed ages ~1400 cal yr BP to Present. The major part of the island formed under stable or slightly rising sea levels before 2100 cal yr BP. Waves and swells would generate, transport and build-up the pebble-sized Pocillopora sediment, and occasional storms/cyclones could have produced the layers with coarser sediment. Results serve as baselines to discuss the island's future in response to sea-level rise and possible increase in storm/cyclone intensities.