Paleomagnetic constraints on the paleogeography of the East Asian blocks during Late Paleozoic and Early Mesozoic times

Although the axial and dominant geocentric character of the Earth's magnetic field means that paleolongitude is indeterminate, paleomagnetism is otherwise the only truly quantitative method available to the Earth scientist for constraining paleogeography and reconstructing the kinematic evolution of continental blocks. During the past half-century numerous paleomagnetic results have provided substantial quantitative constraints on the origin and tectonic evolution of the major tectonic divisions now comprising Eastern Asian. In this paper we first assess the available Early Paleozoic to Early Cretaceous paleomagnetic results from the South China, North China, and Tarim blocks using internationally-recognized reliability criteria. We then construct a running mean through a 20 Ma window by weighting the poles according to their Q-factors and fit a spherical spline with smoothing factor of 300 to derive apparent polar wander (APW) paths for these three major blocks during this Early Paleozoic to Late Mesozoic time interval. Together with Late Paleozoic to Early Mesozoic paleomagnetic poles from the Qaidam, Qiangtang, Lhasa, Sibumasu, Indochina, and some other smaller blocks/terranes of East Asia, we produce a series of paleogeographic reconstructions for these major blocks and lesser terranes of East Asia between mid-Ordovician and late Jurassic times (~460–160 Ma) which, although based primarily upon paleomagnetic evidence, aim to embrace the geological constraints. Finally, we discuss the current evidence for closure times of the Paleo-Asian, Mianlue, and East Paleo-Tethyan oceans which incorporate fundamental issues concerning the formation of the East Asian continental collage and collision with the northern main body of the Pangean supercontinent. We use the collective evidence to argue that these major paleo-oceans had closed by the Late Triassic, and that the East Asian sector of the supercontinent had united to become an integral part of Pangea by that time (~220 Ma).