Drastic change in the geographical distribution of the cold-water nannofossil Coccolithus pelagicus (Wallich) Schiller at 2.74 Ma in the late Pliocene, with special reference to glaciation in the Arctic Ocean

We reconstruct the late Pliocene to Quaternary paleoceanography of the Pacific and Atlantic Oceans based on the geographical distribution of Coccolithus pelagicus (Wallich) Schiller, which has been regarded as a typical cold-water species. At 2.74 Ma, the distribution of C. pelagicus defines a biogeographical boundary in the marginal seas of mid- to high-latitude regions of the Pacific, such as near the Japanese Islands, Kuril Islands, Kamchatca Peninsula, Aleutian Islands, Alaska and the northeastern Pacific off Canada. The relative abundance of C. pelagicus is greater than 80% in these marginal sea areas in the North Pacific and Japan Sea. On the basis of characteristics of the nannofossil assemblages and recent nannoplankton biogeography in the Norwegian–Greenland Sea, the change in the relative abundance of C. pelagicus at 2.74 Ma is thought to be the result of the southward migration of most species except C. pelagicus, with the onset of heavy glaciation. The results also indicate that the geographical distribution of C. pelagicus changed in three steps, at 2.75, 1.65 and 1.2 Ma, and it became rare to barren in low-latitude regions.