Nanokawa thrust of the Northern Chichibu Terrain in Middle West Shikoku
前川, 寛和 大阪府立大学
Northern Chichibu Terrain
In the Northern Chichibu Terrain in Middle West Shikoku, the Nanokawa thrust occurs in the Jurassic accretionary complexes. Along the Nanokawa thrust, greenstones and pelitic semi-schists of the Nakatsuyama Unit are thrust over chaotic formations, sandstones and greenstones of the Niyodogawa Unit. The strata of the Nakatsuyama Unit dip gently and are slightly folded, whereas those of the Niyodogawa Unit dip steeply to the north. Metamorphic minerals of the greenstones of the hanging wall and footwall of the Nanokawa thrust are examined. The greenstones of the hanging wall contain alkali amphibole, alkali pyroxene, stilpnomelane and pumpellyite, and have undergone the pumpellyite-actinolite facies metamorphism. On the other hand, those of the footwall contain prehnite and pumpellyite, and have undergone the prehnite-pumpellyite facies metamorphism. The Nanokawa thrust is a large overthrust, which has a different metamorphic grades between the hanging wall and footwall. The Nanokawa thrust extends toward west to the north of the Torigatayama limestones. The thrust does not extend to the Kurofujigawa thrust, which occurs near the Mikabu greenstones.
nsr_21_65.pdf 2.36 MB