<国立科博専報>地学的にみた伊豆半島

概要

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Although the Izu Peninsula is presently annexed to Honshu, it is not placed on the Eurasian plate but the Philippine Sea plate. To the northward of the Izu Peninsula, the South Fossa Magna folded belt is developed along the boundary between above two plates. The belt has different stratigraphy and geologic structure of the Tertiary to Quaternary from those of adjacent areas, particularly of the Izu Peninsula. The structural characteristics of the South Fossa Magna folded belt are the intense deformation and compression forming a northward-convexing structure and those of the Izu Peninsula are a a blockwise faulting. This is consistent with the idea that the Izu Peninsula collided against Honshu in early Quaternary. There is a theory that the Izu-Mariana Arc had shifted eastward from the south of Kyushu to the present position during the period of 30 Ma-15 Ma, but it is more probable that the arc has been situated at the present position relative to Honshu and had been moving northward to subduct beneath Honshu during that period, and later, until the Izu Peninsula collided against Honshu and annexed to it in early Quaternary, when a marine sedimentary belt between the Izu Peninsula and Honshu was emerged.
国立科学博物館の論文
1982-12-01