31 July 1992
Vol 257, Issue 5070

About The Cover

Coral skeleton of the genus Favia. Scleractinian corals secrete a hard skeleton composed of aragonite (CaCO3), which incorporates strontium along with calcium in a ratio that depends on sea-surface temperature. Recent findings suggest that for corals of the genus Porites this dependence may be used to recover records of Pleistocene and Holocene sea-surface temperatures with an apparent accuracy of better than 0.5°C. See page 644. [Photomicrograph: J. W. Beck]