The oldest rocks in Japan were brought from the Precambrian continent which existed to the north of Japan in the Jurassic era, when the Kamiaso conglomerate was laid down in marine deposits. Today such rocks can be found in Samcheok in the northeast of South Korea, and also in the east of North Korea, far to the north of Samcheok. This gives a clue to the site of the origin of our oldest rocks.