Paleomagnetic constraints on Miocene rotation in the central Japan Arc

Abstract

We present new Middle Miocene paleomagnetic data for the central Japan Arc, and discuss their implications for Miocene rotation. To obtain a refined paleodirection, we made magnetic measurements on basaltic to andesitic lavas and intrusive rocks from 12 sites in the Tsugu volcanic rocks (ca 15 Ma) in the northern part of the Shitara area, Japan. Significant secondary magnetizations in samples with strong magnetic intensities are interpreted as lightning-induced components. Mean directions carried by magnetite and/or titanomagnetite were determined for all sites. An overall mean direction with a northerly declination was obtained from dual-polarity site means for nine sites. This direction is indistinguishable from the mean direction for coeval parallel dikes in the northern part of the Shitara area, and also indistinguishable from the Miocene reference direction derived from the paleopole for the North China Block in the Asian continent. These comparisons suggest little or no rotation or latitudinal motion in the study area with respect to the North China Block since 15 Ma. We obtained a refined early Middle Miocene paleodirection (D = 9.7°, I = 52.5°, a 95 = 4.8°; 30 sites) and paleopole (82.0°N, 230.8°E, A 95 = 5.6°) for Shitara by combining data from the Tsugu volcanic rocks and a coeval dike swarm. An anomalous direction found at three sites could be a record of an extraordinary field during a geomagnetic polarity transition or excursion. Paleomagnetic data from Shitara suggest that: (i) the western wing of the Kanto Syntaxis, a prominent cuspate geologic structure in central Honshu, underwent a counterclockwise rotation with respect to the main part of the southwestern Japan Arc between ca 17.5 Ma and 15 Ma; (ii) collision between the Japan and Izu-Bonin (Ogasawara) Arcs began prior to 15 Ma; and (iii) clockwise rotation of the entire southwestern part of the Japan Arc had ceased by 15 Ma.

Subduction accretion and orocline development in modern and ancient settings: Implications of Japanese examples for development of the New England Orogen of eastern Australia

“…4) that is considered at least partly caused by the collision, although this has been a subject of continuing debate (Amano, 1991;Takahashi and Saito, 1997;Kimura et al, 2014). Palaeomagnetic data collected from rocks around the Kanto Syntaxis by Takahashi and Saito (1997) and Hoshi and Sano (2013) show that formation of the syntaxis was not solely a result of impingement of the accretionary belts by the Izu-Bonin-Marianas arc indentor. Opening of the Sea of Japan in the early Miocene was achieved by a 50° clockwise rotation of southwest Japan from a NNE to an ENE trend (Faure and Lalevée, 1987), thus the western limb of the syntaxis was originally NNE trending (Takahashi and Saito, 1997), although data presented by Hoshi and Sano (2013) indicate that this limb has undergone a 20° anticlockwise rotation associated with the Izu-Honshu collision at 17.5-15 Ma.…”

“…The Kanto Syntaxis (Fig. 4), an orocline formed by the curved Mesozoic-Cenozoic accretionary belts of southwest Japan, is also developed in the Tokyo region of Japan where the Izu-Bonin-Marianas arc is presently colliding with the Honshu arc (Niitsuma, 1989;Takahashi, 1994;Takahashi and Saito, 1997;Hoshi and Sano, 2013). Curved belts not directly caused by collision are also commonly associated with island arcs in general and deformed belts in the western Mediterranean Sea where they are related to rollback and sea-floor spreading in backarc basins (Rosenbaum, 2014).…”

Depositional setting, provenance, and tectonic-volcanic setting of Eocene–Recent deep-sea sediments of the oceanic Izu–Bonin forearc, northwest Pacific (IODP Expedition 352)

“…Basic tuffaceous rocks that are interpreted to have been derived from the Izu-Bonin arc first appear in the Honshu forearc basin in the Boso Peninsula (Amatsu Formation) during the early late Miocene (13-12 Ma) Saito 1997, 1999). Some palaeomagnetic data for mid-Miocene time suggest that amalgamation of the Izu-Bonin arc with Honshu began before 15 million years (Hoshi and Sano 2013).…”

Timing of clockwise rotation of Southwest Japan: constraints from new middle Miocene paleomagnetic results

“…The data from Izumo also suggest that clockwise rotation was complete by 15 Ma. Furthermore, studies conducted in other areas of Southwest Japan have provided timeaveraged mean directions suggesting little or no rotation since 15 Ma (Nakajima et al 1990;Itoh et al 2000;Hoshi et al 2000b;Hoshi and Yokoyama 2001;Tamaki et al 2006;Hoshi and Sano 2013).…”

“…However, this model has been questioned, given the results of a number of paleomagnetic and geochronological studies (e.g., Nakajima et al 1990;Jolivet et al 1995) that cite an absence or lack of data for the rotation of rocks dating from ca. 15 Ma in some areas of Southwest Japan (Hoshi and Sano 2013;Sawada et al 2013; and references therein), thus leading to an alternative view that clockwise rotation occurred before (not at) 15 Ma (e.g., Nakajima et al 1990;Hoshi et al 2000b). However, the majority of such data are from volcanic rocks which have been radiometrically dated by conventional K-Ar or fission track methods, which are subject to significant uncertainties.…”