Microatoll

[2] This definition has been extended to include similar structures built by non-coral reef-building organisms such as serpulid worms, pelecypods and vermetid gastropods.

[5] Microatolls are formed by several species of the genus Porites, but examples have also been described from Acropora, Heliopora, Favia, Favites, Platygyra, Cyphastrea and Goniastrea.

[2] The detailed record of sea level change preserved in fossil microatolls, combined with precise dating of individual annual rings using the Uranium-thorium dating method, allows them to be used to determine past relative sea-level change with uncertainties of about 20 centimeters (7.9 in) in level and a few years to a few decades in time.

[4] They have been used to map the rupture areas of great to giant earthquakes and to estimate the recurrence interval of such events before historic records are available.

[6] Changes in oxygen isotope ratios in fossil microatolls have also been used to provide high-resolution proxy records for sea surface temperature over the last few thousand years.