An analysis of apparent polar wander path for southwest Japan suggests no relative movement with respect to Eurasia during the Cretaceous

Abstract

To test the hypothesis that southwest Japan was involved in large-scale tectonic movement with southward translation as far as 2000km with respect to Eurasia during the Cretaceous, we examined Cretaceous paleomagnetic poles from southwest Japan to compare with those from Eurasia. Red and gray sandstone samples from the Upper Cretaceous Onogawa Group were collected from twelve sites in the Onogawa Basin in the western part of southwest Japan for paleomagnetic analysis. This group formed over the time span in which the proposed tectonic event is hypothesized to have occurred. A characteristic remanent magnetization component was isolated from red sandstone at ten sites; it is interpreted to be of primary Late Cretaceous origin. The primary directions combined with previously reported data provide a mean direction (D=76.8°, I=44.6°, α95=11.1°, N=15) and a paleomagnetic pole (24.4°N, 202.6°E, A95=11.0°) for the Onogawa area. This pole is consistent with other Late Cretaceous poles from a wide area of southwest Japan, and a mean Late Cretaceous pole (28.4°N, 202.5°E, A95=7.5°, N=6) is calculated and regarded as representative of this region. The Late Cretaceous pole, together with mid- and Early Cretaceous poles, constitutes an apparent polar wander path (APWP) for southwest Japan during the Cretaceous. After restoration of post-Cretaceous tectonic rotation, each Cretaceous pole for southwest Japan shows agreement with the coeval poles for Eurasia; therefore, it is unlikely that the previously proposed tectonic model that includes southward translation of southwest Japan occurred in the Late Cretaceous. Southwest Japan is considered to have behaved as a stable part of the Eurasian continental margin during the Cretaceous.