EARLY PLIOCENE CLIMATE - A PERSPECTIVE FROM THE WESTERN EQUATORIAL ATLANTIC WARM POOL

High-resolution (similar to 3-4 kyr) planktonic stable isotope stratig raphies from Site 925 drilled on Ceara Rise (Ocean Drilling Program Le g 154) are used to investigate the role of the western equatorial Atla ntic sea surface hydrography in early Pliocene (3.2-4.7 Ma) climate ch ange. Oxygen isotope results from Globigerinoides sacculifer, a mixed layer dweller, suggest that equatorial sea surface temperatures were c ooler than today by similar to 2 degrees-3 degrees C, consistent with relatively strong northward advection of heat away from the equator. O xygen isotope results from Neogloboquadrina dutertrei suggest that ove r the long term this thermocline dweller tracks global ice volume fluc tuations. Stable isotope gradients between the two planktonic species throughout the entire interval imply a stable warm pool in the western equatorial Atlantic, We observe a rapid (3.4 kyr) decrease in G, sacc ulifer and the N, dutertrei delta(18)O values at 4.36 Ma that may refl ect a freshening of the sea surface, a direct response to a southward displacement of the Intertropical Convergence Zone, and perhaps, an in direct response to restricted flow through the Central American Seaway .