The Akahoya（K-Ah）Tephra was erupted 6300 Y．B．P．from Kikai Island in Kyushu，and　is one of the most widespread marker-tephras in Japan．lt has recently been identified at three sites near Matsue city．These sites are distributed in former wet-land　along the eastern margin of Lake Shinji．Each volcanic ash layer is less than 2cm thick，and is intercalated with brackish silt．Volcanic glass in each layer was analysed by EPMA，and is chemically identicalto that in K-Ah Tephra from elsewhere．