Biogeography of Neogene calcareous nannofossils in the Caribbean and the eastern equatorial Pacific - floral response to the emergence of the Isthmusof Panama

Principal components analysis of nannofossil assemblages in five ODP sites in the Caribbean and the eastern equatorial Pacific was used to monitor Neo gene surface water circulation changes. In 15.83-10.71 Ma, floral distribut ions clearly show the existence of the Circum-tropical Current between the Caribbean and the eastern equatorial Pacific and no surface water communica tion between the northern and southern Caribbean. In 10.71-9.36 Ma, the Cir cum-tropical Current weakened and the northward intra-Caribbean current had been initiated. Northern and southern Caribbean surface waters again becam e separated in 8.35-3.65 Ma and the Circum-tropical Current was regenerated . After 2.76 Ma, the northward intra-Caribbean current has completely been established and the Circum-tropical Current disappeared. This suggests that a barrier to the Circum-tropical Current had formed, indicating the final closure of the Isthmus of Panama. (C) 2000 Elsevier Science B.V. All rights reserved.