At around 900,000 years ago, there was an erosion in South Mount and Kendeng Mountain resulted in the limestone flakes and pebble gravel. Those materials were mixed, and broadly deposited, and resulted in the very hard gravel-coarse stone. In the Grenzbank, many fauna fossils are found.
By the deposited Grenzbank, it marks the changes of sedimentation environment, which is from swamp environment to be land environment. Since then, the marine environment had been disappeared forever from Sangiran. (Suwita Nugraha, Wulandari, Iwan SB)