Magnetostratigraphy of Hominid Fossil Bearing Formations in Sangiran and Mojokerto, Java

Paleomagnetic investigation of Plio-Pleistocene formations in Sangiran and Mojokerto, Java was carried out to date stratigraphic levels of Pithecanthropus fossils. Secular variation records of paleomagnetic field direction from the two areas show very consistent changes with some prominent features. The record for the past 3 million years obtained in Sangiran revises the magnetostratigraphy of earlier investigations and reveals stratigraphic levels of polarity boundaries and events. Based on correlation of the secular variation record of Mojokerto with that of Sangiran, magnetostratigraphy of Pleistocene formations in Mojokerto was established. The stratigraphic zone of Pithecanthropus in Sangiran ranges from the lower boundary of Jaramillo event to the Brunhes/Matuyama boundary, and the stratigraphic level of Homo modjokertensis lies at the lower border of Jaramillo event. Magnetochronologically it dates from about 0.73-0.97 m.y. for Sangiran and about 0.97 m.y. for Mojokerto.