GEOCHRONOLOGY OF DROWNED HAWAIIAN CORAL-REEFS

Two deeply submerged coral reefs were sampled with the HURL submersible Pisces V off the islands of Hawaii and Maul. An ancient fringing reef at 950 m depth on the Kohala dope of Hawaii was observed from deep-towed camera photographs and during submersible operations. A second reef at 1650 m depth on the Haleakala slope of Maul was observed on side-scan images, deep-towed camera photographs and during submersible observations. Ages of the two reefs were determined by electron spin resonance dating with a signal intensity for aragonitic coral at g = 2.0007 used to ascertain the accumulated dose by the additive dose method. Uranium concentration was measured by neutron activation analysis. The chronology of the reefs indicates that drowning coincided with periods of rapid global climate change at the termination of continental glaciation at approximately 250 ka and 340 ka. The drowning events correlate with oxygen isotope stage boundaries 7/8 and 9/10. These data support models of reef drowning on subsiding volcanic edifices.