REORGANIZATION OF DEEP-OCEAN CIRCULATION ACCOMPANYING A LATE CRETACEOUS EXTINCTION EVENT

DEEP ocean circulation may be a significant factor in determining glob al climate(1-5). Increases in the flux of warm, saline waters from low to high latitudes would enhance the poleward transport of heat and, t hus, help maintain the warm conditions at high latitudes typical of gl obally warm 'greenhouse' periods, But controversy exists(1,2) as to wh ether the ocean's thermohaline circulation can transport enough heat t o bring about the temperature distributions of these times, such as th e mid-Cretaceous and early Eocene, Here we present stable-isotope reco rds of ocean temperature and salinity that indicate that bottom waters in Late Cretaceous oceans of the Southern Hemisphere became cooler an d less saline at the same time (about 70 Myr ago) as widespread biotic changes(3,6-8). These findings support the idea that changes in deep ocean circulation can act as a climate switch.