抄録
The occurrence of an Early Campanian planktonic foraminiferal assemblage consisting of Globotruncana arca, G. linneiana, Rosita fornicata and R. patelliformis is first reported from the Upper Haborogawa Formation exposed in the Haboro area, northwestern Hokkaido, Japan. This finding supports the previous interpretation that the Santonian/Campanian boundary can be placed at the basal part of Inoceramus (Platyceramus) japonicus Zone of the inoceramid biostratigraphy.
