Gyliakian Series

Major division of Cretaceous rocks and time in Japan (the Cretaceous Period began about 144,000,000 years ago and lasted about 77,600,000 years). Rocks of the Gyliakian Series overlie those of the Miyakoan Series and underlie rocks of the Urakawan Series. Two stages, the Upper and Lower Gyliakian stages, are recognized and represent shorter spans of time. Distinctive fossil cephalopods