Abstract
The writer descrives a tuff (-breccia) bed, named the Kamisannai Tuff (-breccia), which outcrops in the Iwami-sannai district to the east area of the Yabase oil-field, Akita Pref., showing interesting modes of occurrence, and he also mentions that it may be a deposition of detritus of submarin eruption, and that it is one of the characteristic modes of occurrence of tuff or tuff-breccia in the Akita oil-fields.
