蒲田川流域の地形・地質学的特性に関する研究(2) ―蒲田川流域の地質学的特性について―

Abstract

On the Gainata river basin in Gifu Pref., central Japan, there are various kinds of rapidldnd slide and mud flow. In order to make clear the genetic mechanism of the landslide, it is necessary to observe the geologic structure of the basin such as arrangementof rocks and deposits.It was classified from the authors' observation that geology and geologic structure inthis basin, are made of both the older basement rocks consisted of Paleozoic involvingMesozoic igneous rocks and the young Quaternary deposits consisted of volcanic materialand delluvial and sedimentary deposits.In this area, the main geologic structure in the basement rocks is characterized bythe Circuin Hida tectonic zone, which was made of complex of metamorphic and plutonicrocks, and developed duaring the period from the formation of pre-Cainbrian schist tothe post Mesozoic igneous activity.It was also presumed, on the other hand, that the gigantic mass, the so-calledNohi-rhyolite mass was active in the late Mesozoic along oblique trend to the preexistingwas tectonic zone.The young deposit in the Quaternary is classified as the volcanic materials in theYakedake volcano, located in the Norikura-volcanic zone, and the terrace deposits inPeistocene epock. In this area, these terrace deposits are formed by erosion of preexistingstrata.