9:45 AM - 10:00 AM
[HQR05-04] Tephrochronology of the lowest Kazusa Group distributed in the Boso Peninsula, Chiba Prefecture , Japan
Keywords:Kazusa Group, Age, Namihana Formation, Katsuura Formation, Widespread tephra correlation, Tephrochronology
In order to characterize the tephra layers with in the lowest Kazusa Group, authors investigated the thickness, color, shape of volcanic glass, mineral composition, refractive index of volcanic glass and the majer and trace element composition of volcanic glass. Two tephra layers in the Namihana and the Katsuura Formation of the lowest Kazusa Group can be correlated with tephra layers of the other Plio-Pleistocene Groups in central Japan. The KW1 and KW2 tephra layers in the lowest Kazusa Group are correlated with the Jwg3-Okr10 tephra(2.388 Ma) and Fup-OK2 tephra(2.2-2.3 Ma). The age of the lowest Kazusa Group is about 2.4 Ma by these tephra correlations.