The ophiolite-like complex in the Green-Tuff geosyncline consists of basic effusive and intrusive rocks, and fine grained sedimentary rocks such as siliceous and black mudstones, all of which have been formed along the frontal margin of the initial basin in the geosyncline at the early stage. They may be regarded to correspond to the ophiolite, though the ultrabasic rock is not observed. A scheme on the development of the geosyncline in the Green Tuff region is presented in Fig. 1. Similar scheme can be applied to the Mesozoic and Paleozoic geosynclines in the Japanese islands.