Latest Quaternary Paleoceanography of the Oga peninsula, Japan Sea side of Japan: glaciatin in MIS 12 as evidenced by lithostratigraphy and nannofossil biostratigraphy

The uppermost Quaternary Wakimoto Formation, distributed in the northern part of Oga Peninsula, is composed of sandy siltstone, siltstone and alternation of very fine sandstone and sandy siltstone. The formation is divided into seven lithostratigraphic Units. The upper part of the formation is divided into seven lithostratigraphic units. Unit 1, situated in the lowest part of the studied section, is composed of poorly laminated sandy siltstone. The unit is also characterized by presence of isolated granule to pebble gravels which are interpreted as IRD (ice rafted debris). Lithology of units 4 to 6, the upper part of section, is changed to siltstone, and unit 7, the uppermost unit of the section, is characterized by sandy siltstone to siltstone with carbonaceous matters. The shibikawa Formation, conformably overlies the Wakimoto Formation, is composed of hummocky stratified sandstone and lignite bed. These lithostratigraphic changes indicates that the sedimentary environment was changed from upper bathyal to neritic or brackish environment. The Pumice tuff layer (B-Og) situated in the lower part of Shibikawa Formation, is correlated to Top of MIS 12. Calcareus nannofossil study also indicates that the unit 5 in the upper part of the Wakimoto Formation is traceable to just below the peak of MIS 12 based on the top datum of Pseudoemiliania lacunosa. From these facts that the studied section is correlated to the upper part of MIS 12, and the area was influenced by iceberg around 450ka as evidenced by presence of IRD.;