MOORE 9302487 This project will use stable isotopes and assemblages of two groups of microfossils to provide a detailed reconstruction of surface water circulation in the eastern equatorial Pacific through the Pliocene. The authors hypothesize that closing of the Isthmus of Panama led to conditions which created the warm fresh pool of water observed in the area today, and that the pool in turn is responsible for the modern equatorially-asymmetric circulation. They hope to determine the relationship of these events to the increase of northern hemisphere glaciation documented elsewhere.