The Yezo Group and the Kwanmon Group

Abstract

Bearing in mind the rule of the stratigraphical nomenclature, which is now under discussion among the Japanese geologists, I am going to propose the new name of the Japanese Cretaceous formations., What have been called the Lower Ammonite Beds or group, the Middle Ammonite group, the Trigonia Sandstone and the Upper Ammonite group in Hokkaido are to be revised as the Lower Yezo group, the Middle Yezo group, the Mikasa subgroup and the Upper Yezo group respectively., The boundary between the Lower and the Middle Yezo groups is here redefined., The so-called "Inkstone Series" in the Inner Zone of Southwest Japan is to be replaced by the following name, according to the newly established stratigraphical column of the type area., the Kwanmon group Upper: the Shimonoseki subgroup Lower: the Wakino subgroup