Abstract
The origin of the dolomite which occurs beneath the atolls of Funafuti, Kita-daitō-jima, and Eniwetok in the Pacific Ocean can be explained by the reaction of hypersaline brines with transported or buried reef skeletal material. Dolomitization could have taken place at the sediment surface in shallow restricted back-reef lagoons and tidal flats or below the surface by reflux action. Measurements of oxygen isotopes in samples of dolomite can be interpreted as indicating an origin from evaporated, isotopically-heavy sea water.