Global Sea surface stability and significant paleoceanographic episodes between the western Equatorial Pacific, Bahama Bank of Caribbean, and western Pacific Ocean during the Neogene based on calcareous nannofossil productivity and size variations in correlation to the global climatic events

We investigated the calcareous nannofossils assemblages to reconstruct the Neogene paleoceanography of Bahama Bank of Atlantic, Equatorial Pacific and western Pacific Ocean from the ODP Sites 1007, 805, and 782 and correlate with the global events. The absolute abundant of coccolith (number/g) are gradually increased from NN2 throughout NN19 Zone, while the relative abundance of Discoaster is decreased at Sites 782 and 805 in the western Pacific and western Equatorial Pacific Ocean. The maximum size of Reticulofenestra increased until 8.8 Ma which shows the oligotrophic conditions with sea surface stratification and thermocline (Fig.). The changes of the modal and maximum size of Reticulofenestra which are strongly reflected the collapse of sea surface stability, show four times in 8.8 Ma, 6.4 Ma, 5.4 Ma and 3.75 Ma at Site 782, and in 15.4 Ma, 8.8 Ma, 5.4 Ma and 3.75 Ma at Site 805. On the basis of relationship between the changes of maximum sizes of Reticulofenestra and nutrient condition, these eutrophication events are clearly traceable to the western Pacific, Bahama Bank, and to the Equatorial Pacific Ocean. Two paleoceanographic events found in 8.8 Ma and 3.75 Ma are interpreted as change to high nutrient condition resulted in the intensify of Asian Monsoon and closure of Panama Isthmus.