新潟県十日町市松代に分布する泥火山の地質  [in Japanese] Mud volcanoes in Matsudai, Tokamachi City, Niigata Prefecture  [in Japanese]

We found and described two active mud volcanoes (abbr.: MV), i.e., Gamo MV and Murono MV, and one extinct mud volcano (Shosenji MV) in Tokamachi City, Niigata Prefecture. Active MVs are distributed along the wing of an anticline axis. High saline groundwater, inflammable gas and clay less than 2μm in diameter are erupted from both active MVs. Shosenji MV is exposed near the Gamo MV at a road construction site. Horizontal and vertical structures of the extinct mud volcano, consisting of mud breccia and scaly network clay can be observed. The activity of mud volcano is closely related to the formation of swelling mudstone in the Nabedachiyama Tunnel excavated at the depth of 150m under Gamo MV and Shosenji MV.