In Sendai area, enormous volume of volcanic rocks erupted as pyroclastic flows or lava flows during the early Miocene to late Miocene in time. These volcanic rocks consist mainly of calc-alkaline andesite and dacite, with subordinate amounts of tholeiitic basalts and andesites.
New analyses are presented for 20 representative calc-alkaline andesite-dacite and 12 tholeiitic basalt-andesite. All of the volcanic rocks are characterized by high CaO and very low Na2O and K2O, and Galc-alkaline series are very similar to those of the tholeiite province of the Quaternary volcanoes in northeastern Japan.