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doi:10.2204/iodp.proc.319.202.2013

Results

Eighteen genera and 41 species were recognized in the Neogene and Quaternary sequences of Hole C0009A except for some Noelaerhabdaceae taxa. Generally speaking, abundant nannofossils occurred throughout the section and preservation of specimens is good. Florisphaera, Reticulofenestra, and Gephyrocapsa occupied ~80%–90% of total flora throughout the section (Fig. F2). Other taxa are rare although it was easy to find some stratigraphically important species. Thirteen nannofossil datums were recognized in the sediment in Hole C0009A (Figs. F2, F3). Most of the datums determined in this study are consistent with those observed by Expedition 319 Scientists (see the “Site C0009” chapter [Expedition 319 Scientists, 2010b]), further confirming previous results. Moreover, the disappearance of comparatively larger Reticulofenestra specimens (≥6 µm) at 1147.7 m MSF seems to correspond to one of the upper Pliocene datums that were defined by sudden reduction of maximum size Reticulofenestra specimens (Kameo and Takayama, 1999).

There are some unconformities and/or intervals of substantially slow sedimentation in the Neogene sediment in Hole C0009A. As already mentioned by Expedition 319 Scientists (see the “Site C0009” chapter [Expedition 319 Scientists, 2010b]), a major unconformity exists that corresponds to the boundary between lithostratigraphic Units III and IV (5.6–3.8 Ma). In addition, minor unconformities and/or condensed sections should be present between 842.7 and 852.7 (~1 Ma), 900.2 and 907.7 (~1.3 to ~1.6 Ma), and 930.2 and 955.2 m MSF (2–2.5 Ma). According to the correlation with previous NanTroSEIZE drilling sites, sediment ages at Site C0009 are mostly consistent with those at Site C0002 (Fig. F2). However, the Pleistocene sediment (Unit II at Site C0002) is much thicker than at Site C0009 but reversed for the Pliocene. The ages right above the unconformity (between Units IV and III) are different at both sites, and the base of Unit III at Site C0009 is younger. This implies that the sedimentation at Site C0002 resumed earlier than Site C0009 at the Kumano Basin.

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