抄録
The Takurayama Volcano is located at the border of the Kyoto and Hyogo Prefectures in the northern part of the Kinki District. The volcano is composed of basaltic lava plateau named Yakunogahara, and scoria cone, Mt. Takurayma, with crater-like depression. It is the most eastern volcano among the alkaline basaltic volcanoes of the San-in province. The Quaternary deposits around the Takurayama Volcano are divided into four formations on the basis of their relationships with the Takurayama volcanism, those are pre-volcanic Mizaka Formation, syn-volcanic Yakunogahara Formation, and post-volcanic Kamiyakuno Formation and terrace deposits. The Mizaka Formation is composed of silty clay and sand with plant remains deposited in a rather stable lake existed prior to the commencement of the volcanism. This formation was deposited in a certain time of middle Pleistocene (between Ma4 and Ma7 of the Osaka Group). The Yakunogahara Formation was deposited in ponds dammed up by the lava flow. This formation is late Middle or early Late Pleistocene in age (later than the deposition of Ma8 and earlier than the formation of Middle Terrace). The Kamiyakuno Formation is the deposit of the small depression on the lava plateau in the glacial age of Wurm. The terraces are divided into the upper and lower ones, which are correlated to the Middle and Low Terraces, respectively. The lower terrace was formed in the glacial age of Wurm. Basaltic gravels derived from the volcano are contained in both the lower and upper terrace deposits. Volcanism of the Takurayama Volcano took place in late Middle or early Late Pleistocene, because it is contemporaneous with the deposition of the Yakunogahara Formation.
