Age of Beachrock containing the Jomon Pottery in the Goto Islands

In 1964 the senior writer reported the occurrence of beachrock from the beach exposed along the west coast of the entrance of Ogushi Bay in the western part of Narushima in the Goto Islands, and he discussed on the age and origin of the beachrock containing the pottery of the Sobata type and concluded its age to be of the early Jomon period by the occurrence of this pottery.On the other hand, Esaka published different opinion on the age of this beachrock in 1967 and he considered its age to be rather younger than the period indicated by this early Jomon pottery.In the present paper, the writers especially discussed on the age of the beachrock upon the basis of the 14C dating of the shells cemented in the beachrock and the field work as follows.1. The shells included in the beachrock is dated as 5, 650±150y. B. P. (Gak. 2861). The age of this beachrock is therefore thought to belong to the early Jomon period.2. It is considered that the sea level in the Goto Islands has been comparatively stable during the past about five thousand years since the early Jomon period.3. Judging from the origin of beachrock, the climatic condition of the early Jomon period is presumed to have been warmer than that of the present day.