William R. Dickinson

Dept. of Geosciences, University of Arizona, Tucson, Arizona 85721, USA;

Modern atoll reefs began to grow after rising postglacial eustatic sea level overtopped degraded carbonate platforms that had been exposed as subaerial limestone plateaus during synglacial drawdowns in sea level. Stable atoll islets atop emergent paleoreef flats did not begin to develop until after the mid-Holocene hydro-isostatic sea level highstand in the tropical Pacific Ocean. Atolls have been occupied since stable islets formed during the last two millennia. Rising global sea level will impact atoll environments adversely for continued habitation once ambient high-tide level rises above the mid-Holocene low-tide level. That crossover will submerge the resistant paleoreef flats that underpin stable atoll islets and subject their unconsolidated sediment cover to incessant wave attack before ambient sea level actually overtops the islets.

Received: November 24, 2008; Accepted: December 24, 2008

DOI: 10.1130/GSATG35A.1