Stratigraphy and Ammonite Fauna of the Jurassic System of the Southern Kitakami Massif, Northeast Honshu, Japan

Stratigraphical and paleontological studies were undertaken of the Jurassic System distributed in the Central Belt and Western Belt of the Southern Kitakami Massif. The Eastern or Outer Belt is not distributed in the area studied. The Central Belt comprises two areas, the northern or Karakuwa and the southern or Ojika, and the Western Belt includes four areas, the northernmost one or Chonomori, the Shizukawa, the Hashiura-Jusanhama, and the Mizunuma. These areas are separated from one another by tectonic lines. The northernmost area is omitted in this work because of lacking paleontological evidence for its reference to the Jurassic. Stratigraphical work was undertaken to determine the horizons of the ammonites for establishment of a biostratigraphic standard for the Jurassic System of the Southern Kitakami Massif. The evolution of each sedimentary basin, stratigraphic position of the ammonites in each of the separated areas, interrelation of the respective basin, structural growth of the Jurassic terrain and correlation with other areas was undertaken. Systematic classification and description of 42 genera with 80 species among which 9 species represent undescribed forms of the Jurassic ammonites are given in this work