We studied the sequence of the middle Miocene to Pleistocene of each Holes. The calcareous nannofossils are generally abundant and preservation is moderate to good in the site 782. However, calcareous nannofossils in site 1007 are moderately to poorly preserve.

We analyze the number of coccolith productivity, Discoaster productivity and size variations of Reticulofenestra

FO: first occurrence; LO: last occurrence.

FO: first occurrence; LO: last occurrence.

to reconstruct the Neogene paleoceanography of Bahama Bank of Atlantic and western Pacific Ocean (Figure 6, Figure 7).

The coccolith productivity of site 782 is characterized by increasing from NN6 to lower part of NN8-NN10 Zone while the relative abundant of Discoaster species shows opposite trends in this interval. The mode and maximum size of the Reticulofenestra show five times increasing patterns while the mode indicates bimodal (Figure 6). The general patterns of maximum of Reticulofenestra are indicated by decreasing in this sequence from 14 Ma to recent. The change in relative abundance and productivity of coccolith are also closely related with the stepwise change in the modal size of Reticulofenestra in NN10, NN11, NN17 and NN19 Zone (Figure 6).

Although the coccolith and Discoaster productivity of Site 1007 located in the Bahama Bank is not changed clearly during Miocene sequence, coccolith productivity suddenly increased in the early Pliocene of NN12 to NN16 (Figure 7). The mode and maximum size of the Reticulofenestra show two times increasing patterns while the mode indicates bimodal (Figure 7). The dominance of small Reticulofenestra in 8.8 Ma are positive correlation with coccolith productivity.

Figure 8 shows the correlation of coccolith number, relative abundance of Discoasters, and maximum size of Reticulofenestra between sites 782 and 1007. The drastically decreasing of maximum size of Reticulofenestra at 8.8 Ma in the late middle Miocene and 3.75 Ma in the late early Pliocene is found in both sites.

Focusing to paleoceanography analysis, nannofossil has been described as a good tool for reconstruct the oceanographic condition. Molfino and McIntyre [2] described the utility of Florisphaera profunda assemblages which shows the stability of sea surface condition. However, as Florisphaera profunda first appears in late Neogene, it’s impossible to analyze the Neogene paleoceanographic conditions based on Florisphaera profunda assemblages. Recently, Sato and Chiyonobu [8] focused to Discoasters for paleoceanographical analysis. Discoasters had been believed the warm water species based on distributions in low latitude region [15] - [17] . However, Aubry [5] , Chepstow-Lusty [18] , Stoll et al. [6] , and Sato and Chiyonobu [8] described that Discoasters lived in lower photic zone of oligotrophic environment and its ecology is similar to Florisphaera profunda.

This means that abundant occurrence of Discoaster indicates the distribution of stable sea surface condition with thermocline and nutricline.

On the other hand, distinct size variations of Reticulofenestra in the Miocene sequence are reported by many authors [8] - [11] [19] - [22] . Hagino et al. (2000) suggested that small specimens of Reticulofenestra were more abundant in eutrophic surface waters than in oligotrophic surface waters [23] . Recently, Sato and Chiyonobu (2009) studied the size variations of Reticulofenestra in the middle Miocene sequence in Pacific Ocean, and described that the presence of large size Reticulofenestra shows the stable and oligotrophic sea surface condition [8] . On the basis of the these phenomena, Farida et al. (2012) suggested that the collapse of thermo- and nutri-cline occurs step by step during Miocene to Quaternary at ODP Hole 805B in the western equatorial Pacific Ocean based on Discoaster relative abundance and the Reticulofenestra size variations [9] . These studies also indicated that the collapse of the stability of the sea surface stratification in the equatorial western Pacific Ocean has been changed in steps by steps from oligotrophic to eutrophic conditions during the Miocene to Quaternary.

Based on these results, we interpret the paleoceanographic environment in the study area. The maximum size of Reticulofenestra increased until 8.8 Ma which shows the oligotrophic conditions with sea surface stratification and thermocline. However, the maximum size of Reticulofenestra suddenly decreased at 8.8 Ma, 5.4 Ma, 3.75 Ma and 2.516 Ma. This means that the stabilization of the Ocean condition in the western Pacific Ocean collapse at 8.8 Ma, 5.4 Ma, 3.75 Ma and 2.516 Ma as a result of change to eutrophic sea surface conditions (Figure 8).

We also make comparison between our results and those studied previously in the Indian Ocean (Young, 1990) [11] and in the northwestern Pacific Ocean (Imai et al., 2015) [10] . Young [11] present three bimodalization occurred in the Indian Ocean sites from NN6 to NN16 Zone at 8.8 Ma; 5.4 Ma; and 3.75 Ma (Figure 9). The strong decreased maximum size of Reticulofenestra coccoliths is present in 8.8 Ma. These events are responsible for the change of sea surface stability in the Indian Ocean. Imai et al. [10] studied calcareous nannofossil assemblages from ODP holes 1210A in the northwestern Pacific Ocean also present the large number of Reticulofenestra coccolith indicates a shallow thermo- and nutricline is drastically change to the small size in six times (in 8.8 Ma, 6.4 Ma, 5.4 Ma, 3.75 Ma, 3.4 Ma and 2.75 Ma) in this sites. Figure 9 shows the changes of mode

size of Reticulofenestra. This indicates that the mode size decreased four times throughout the sequence in 8.8 Ma, 6.4 Ma, 5.4 Ma and in 3.75 Ma (1, 2, 3, 4 in Figure 9). Furthermore, these events are also traceable to the western Pacific, Bahama Bank, Indian Ocean and to the northwestern Pacific Ocean. This means that the sea surface stability of the world ocean was collapsed four times during Neogene time. Furthermore, compared with other sites, northwestern Pacific Ocean is also characterized by the strong eutrophication in 8.8 Ma, 6.4 Ma, 5.4 Ma and at 3.75 Ma based on size variations.

These results indicate that nannofossil events recognized in this study show the drastic changes of paleoceanography in the world occurred four times throughout the Neogene. Especially the events are distinct in the Pacific Ocean.

Many global tectonic and climatic events occurred in the Neogene have been studied. We compare the present investigated results of the size variation of Reticulofenestra in the western Pacific Ocean and Caribbean sea with those in Indian Ocean [11] and northwestern Pacific [10] (Figure 9). Changes of Reticulofenestra maximum and mode size which are strongly related to the collapse of stability of Ocean surface are clearly traceable to these oceans. Among these events, two of them are found in the oceans distinctly. These are as follows:

Event ①: Found in the uppermost NN10 Zone in the late Miocene (8.8 Ma; Figure 9)

Event ④: Found in the NN15/NN16 boundary in the Pliocene (3.75 Ma; Figure 9)

The changes of maximum size of Reticulofenestra are strongly influenced by collapse of sea surface stability related to disappearance of nutricline by upwelling. Based on the characteristics on relation between size variability and nutrient condition, these nannofossil events are interpreted as change to high nutrient condition resulted in the changes of Global climate system. During 8 Ma and 10 Ma is characterized by the intensify the

Asian Monsoon caused by uplift of Tibetan Plateau [24] - [27] . This means that Event ① recognized in 8.8 Ma in the Indian Ocean, Bahama Bank of Atlantic Ocean, and western Pacific Ocean are strongly influenced by the intensify the Asian Monsoon.

Event ④ of 3.75 Ma is strongly related to formation of Panama Isthmus. Haug and Tiedman [28] described that current system across the Panama Seaway was changed from 4.6 Ma and intensification of northern hemisphere glaciation was pronounced between 3.1 Ma and 2.5 Ma. Kameo and Sato [21] , Sato et al. [29] , and Bartoli et al. [30] also described the final closure of Panama Isthmus was established around 2.75 Ma based on nannofossil assemblages and isotope stratigraphy. On the basis of these facts, drastic decrease of maximum size of Reticulofenestra occurred in 3.75 Ma was strongly influenced by closure of Panama Isthmus.

The additional events ② and ③ in Figure 9 found in northwestern Pacific and Indian Ocean (Figure 9) which are indicated by maximum size changes of Reticulofenestra, is correlated to the formation of hiatus in the western Pacific Ocean and Bahama Bank (Figure 9). These two events are correlated to 6.4 Ma and 5.4 Ma. The ages of these events are also respectively correlated to global events as formation of western Antarctic ice sheet and Messinian salinity crisis. Krijgsman et al. [31] presented astronomically calibrated chronology for the Messinian salinity crisis. They show that the onset of the Messinian salinity crisis at 5.96 ± 0.02 Ma and also isolation from the Atlantic Ocean was established between 5.59 and 5.33 Ma. Messinian salinity crisis event influenced to changes of sea surface stability conditions in the global sea level [32] [33] . This indicates that the event ③ in 5.4 Ma indicated by size changes of Reticulofenestra, is strongly influenced by Messinian Salinity Crisis.