Stratigraphy and Geological Structure of the Sanbagawa Crystalline Schist in the Northern Part of the Tenryu River District

Abstract

The Sanbagawa crystalline schist of this district can be divided lithologically into the following formations., Yosizawa formation Black schist of pelitic origin, interbedded with some beds of green schist., Thickness : 350∼650m., Zihati formation Alternating beds of green schist (albite spotted and nones-potted) and black schist (albite spotted and nonspotted)., Thickness: 300∼700m., Wasanma formation Quartz schist; limestone schist; alternation of sericite schist, black schist and green schist beds., Thickness: 300∼400m., Sinkai formation Black schist., Thickness: 500∼600m., Hunayo formation Black schist., Thickness: 700m+., The Yosizaya and the Zihati formations are characterized by a folded structure which strikes east-west., Linear structures can be seen aligned east-west in the cleavage plane which is parallel to the bedding of the Yosizawa formation., The linear structures of the Zihati formation are aligned both east-west and north-south and are formed to the plane or cleavage which is parallel to the bedding plane., Parts of the wasanma and the Sinkai formation are characterized by east-west intraformational folding formed by slip movement in the cleavage plane, S1 parallel to the bedding plane., Linear structures can be seen aligned east-west on the cleavage plane S1, and parallel to the axis of the intraformational folds., In addition, north-south linear structures can be seen on the cleavage plane S2 which can b3 found in a position corresponding to that of the axial plane of the intraformational folds., The Hunayo formation and the lower Sinkai formation are characterized by a north-south structure., Linear structures are found oriented north-south within cleavage planes which are parallel to the bedding plane., Analysis of the linear structures in the crystalline schist formation of this area infers that the orogenic movement can be divided into the following two stages., 1st stage: A north-south differential movement or formations above the lower Sinkai formation and an east-west differential movement of formations below the lower Sinkai formation., Intrusion of the Tatuyama metadiabase sill into spaces between formations which had suffered separate differential movements., 2nd stage: An east-west differential movement throughout the whole Sanbagawa crystalline schist formation in this region.,