古第三紀桜江コールドロン南縁部の地質構造

The southern margin of the Sakurae cauldron，previously the last unsurveyed area，has now been studied in detail．The Sakurae cauldron is filled with the Nakano Formation of the Sakurae Group．The lowermost part of the Nakano Formation is exposed in the study area．It consists of rhyolite lava，fine tuff，crystal tuff，lapilli tuff，welded tuff，and andesite lava layers，inascending order．These are in fault contact with the upper Nakano Formation，and the fault probably strikes WNW-ESE．This is a hinge fault，the displacement of which increases toward the SE．The fault-block on the south side is tilted to the north due to the intrusion of the Yagami granodiorite．