Godai Development Corporation, Japan

The Pliocene to Pleistocene geographical distribution of Coccolithus pelagicus (calcareous nannofossil) in DSDP-ODP samples collected from the Pacific, Atlantic, and Indian Oceans and the Caribbean Sea can be used to reconstruct paleoceanographic conditions. C. pelagicus is interpreted as being a cold water species throughout the Pliocene and Pleistocene. The geographical distribution of this species indicates that a change in the current system around the western Pacific and eastern Atlantic occurred at 2.75 Ma and was related to the final elevation of the Isthmus of Panama. Warm current communication between the equatorial Atlantic and the equatorial Pacific was cut off as a result of the closure of the Central American Seaway. The cold currents from western California, which originated in the North Pacific, flowed into the eastern equatorial Pacific. This is illustrated by the occurrence and the increase in abundance of Coccolithus pelagicus. During this time the warm, eastward flowing equatorial Atlantic current (Paleo-Gulf Stream) turned toward the northeast and penetrated northward along the coast of England. This is evidenced by the decrease in the number of C. pelagicus in the northeast Atlantic between 2.75 Ma and 1.65 Ma.