The growth of large, bank-barriercoral reefs on the Bahamian islands of Great Inagua and San Salvador during the last interglacialwas interruptedby at leastone major cycle of sea regressionand transgression. Thefall of sea level resulted in the development of a wave-cutplatformthat abradedearly Sangamoncoralsin parts of the Devil's Point reef on Great Inagua, andproducederosionalbreaks in thereefal sequenceselsewherein the Devil's Pointreef and in the CockburnTown reef on San Salvador. Minor red calicheandplant trace fossils formed on earlier interglacialreefal rocks during the low stand. The erosional surfaces subsequently were bored by sponges and bivalves,encrustedby serpulids, and recolonizedby corals of youngerinterglacial age during the ensuingsea-level rise. Theselater reefal depositsformthebase of a shallowing-upward sequencethat developedduringtherapid fall of sea levelthat marked the onsetof Wisconsinan glacialconditions. Petrographicstudies reveal a diagenetic sequencethatsupportsthis sea-levelhistory. Preservationof pristine coralline aragonite, coupled with advancesin U/Th age dating, allow theseeventsin the history of the reefs to be placed in a precisechronology. We use thesedata to show that there was a time windowof 1,500yearsor lessduringwhich the regression/transgression cycle occurred, and that rates of sea-levelchange must have been very rapid. We compare our results with the GRIP ice-coredata, and show that the history of the Bahamian coral reefs indicates an episode of climate variability during the last interglacial greater fuan any reported in what is widely believed to be the more stable climate of the Holocene interglacial.
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