Discovery of Aso-4 ash and drift pumice of Aso-4 pyroclastic flow and Sambe-Kisuki pumice fall deposits in the Upper Quaternary of the Oga Peninsula, Akita Prefecture, northeast Honshu, Japan

Abstract

A volcanic ash and two different drift pumices were detected in the Upper Pleistocene Katanishi Formation, Oga Peninsula, Akita Prefecture, Northeast Honshu, Japan. On the basis of the petrographic and stratigraphic studies of these tephras, it is concluded that the ash is the Aso-4 ash ejected at about 70 ka BP from the Aso Caldera, Central Kyushu, one of the most prominent marker tephras of the Late Pleistocene in Japan; one of the drift pumices which lies just on the Aso-4 ash on the Anden coast is identified as the Aso-4 pyroclastic flow deposits, and the other, found in the uppermost part of the Formation at its type section, is identified as Sambe-Kisuki pumice fall deposits which erupted at about 80-90 ka BP from the Sambe volcano in Shimane Prefecture, San' in District, Southwestern Honshu, Japan. Based on this study, stratigraphic and paleo-oceanographic evaluations are obtained. -from English summary