Lithology, structure and correlation of the Hirayu Complex in the Mino Belt of the Takayama area, Gifu Prefecture, central Japan

Abstract

Middle Jurassic melange of the Hirayu Complex, which is an accretionary complex in the Mino Belt, crops out in the Takayama area, Gifu Prefecture. The melange is composed of a matrix of either black mudstone or gray siltstone enclosing clasts of massive sandstone, bedded units of sandstone and mudstone, felsic tuff, brownish siliceous mudstone, red mudstone, gray siliceous claystone, chert, limestone and mafic volcanic rocks. The Hirayu Complex structurally overlies the Yukawa Complex composed of alternating beds of sandstone and mudstone intercalated with chert, and underlies the Kohachigagawa Complex composed mainly of slabs of chert, limestone and mafic volcanic rocks. Shear zones of foliated cataclasite occur along the thrusts bounding these complexes. From the lithological and structural viewpoints, the Hirayu Complex can be correlated to the Middle Jurassic melange of the Kuze Unit in the Mino area, Gifu Prefecture.