9306153 Geary PIs will document environmental changes in shallow-water fauna, associated with emergence of the Isthmus of Panama. Using stable isotope analyses of surface- and bottom-dwelling foraminifera, they will 1) determine age of final closure of the seaway; 2) document environmental divergence on either side of the isthmus, and 3) generate chronologic profiles of environmental conditions across the shelf through the period of circulatory restriction and cutoff. Study will be integrated with ongoing work on mollusks and deep-sea forams. Together studies should provide framework for interpreting evolutionary and ecological patterns associated with this event.
