FISSION-TRACK AGE OF MIOCENE KN-3 TUFF IN CENTRAL JAPAN - TOWARDS BETTER AGE-CONTROL ON MAGNETO-BIOSTRATIGRAPHIC TIME-SCALE

A fission track age for a Miocene tuff(Kn-3) in the late Cenozoic sedi mentary sequence in the Bose Peninsula, central Japan, was determined in an effort to gain an age control for the biozone boundary. The obta ined age of 15.0 +/- 0.5 Ma (error: 1 sigma) represents the N.9/N.10 b oundary of the planktonic foraminiferal zones, as the Kn-3 Tuff is loc ated near the first occurrence of Globorotalia peripheroacuta which de fines the N.9/N.10 boundary. Our age determination supports most of th e recent estimates for the N.9/N.10 biozone boundary which until now h as not been dated directly, but inferred based on speculative assumpti ons.