Paleomagnetism of the Chichibu Quartz Diorite

Constraints on the Time of Lateral Bending of the Kanto Syntaxis

Abstract

Paleomagnetic directions have been determined on Late Miocene diorite bodies in the Kanto Mountains in an effort to clarify the timing of lateral bending of the Kanto Syntaxis. A mean paleomagnetic direction (D=3.5°, I=64.4°, α₉₅=5.1°) of the Chichibu Quartz Diorite, obtained from 21 samples, shows no significantly deflected declination. This indicates no tectonic rotation of the Kanto Mountains since intrusion of the Chichibu Quartz Diorite (6-8Ma). This result signifies that the cusp in the pre-Neogene zonal structure (Kanto Syntaxis) was formed in the Late Miocene or earlier.