Margin-parallel translation in the western Pacific: Paleomagnetic evidence from an allochthonous terrane in Japan

A new paleomagnetic study illustrates latitudinal translation of ribbon-shaped continental fragments along the western margin of the Pacific Ocean. Though tectonic translations have long been recognized as prominent features in the eastern Pacific margin (i.e., North American Cordillera), we present new, quantitative evidence for similar, margin-parallel motion through large-scale, strike-slip faulting in the western Pacific margin. The Kurosegawa Terrane in Southwest Japan is an attenuated tectonic sliver and considered to be allochthonous with respect to the main part of Southwest Japan. Late Triassic and Early Cretaceous sedimentary rocks from the terrane yielded paleolatitudes of 4°N and 18°N, respectively. Based on paleomagnetic data of the Kurosegawa Terrane and plate reconstructions of East Asia, we suggest that the terrane was the easternmost element of the South China Block at least from the Late Triassic to the Early Cretaceous. The terrane was then translated ~ 1500 km northward from the continental margin to its present position, associated with sinistral strike-slip movement along the East Asian continental margin in mid- to Late Cretaceous times. The average displacement rate is calculated to be 7 cm/yr and is comparable to rates reported for the eastern Pacific margin.