PALEOCEANOGRAPHIC CONDITIONS DURING THE CRETACEOUS GREENHOUSE WORLD IN THE CARIBBEAN REGION: IMPLICATIONS TO TROPICAL OCEANS AND CLIMATE CHANGE

Major uncertainties surround how oceanographic conditions in tropical oceans may be modified by global greenhouse climates. Geologic evidence from the Cretaceous Greenhouse World suggests that ocean circulation, a major temperature buffer in today’s tropical oceans, failed during the Cretaceous. Overheating in the tropics led to decimation of reef-building corals and the evolution of the reef-builder rudist bivalve. Herein, the hypothesis to be tested is that variations in the Cretaceous reef-building community were determined by superheated and hypersaline periods that occurred episodically in the central paleotropics (i.e. Supertethys). Cretaceous paleoceanographic conditions such as temperature and salinity are being investigated using fluid inclusions and stable isotopes analyses in preserved reef ecosystems in the Caribbean. Preliminary δ¹⁸O and fluid inclusions analysis derived from Upper Cretaceous rudists and submarine cements indicate sea surface temperatures of ~32°C and salinities of ~40 ppt dissolved salt in seawater. Modern reef building corals can tolerate temperatures 16-30°C and salinities that range from 30-40 ppt. This limited data suggests that changes in greenhouse oceanographic conditions would be a major stressing factor for reef building corals in modern tropical oceans.