A Closure of the Mongol-Okhotsk Ocean by the Middle Jurassic: Reconciliation of Paleomagnetic and Geological Evidence

The late Mesozoic closure of the Mongol-Okhotsk Ocean (MOO) is critical for understanding the tectonics of East Asia. There is a considerable mismatch (similar to 40 million years) between the timing of MOO closure based on paleomagnetic data and geological evidence. We review paleomagnetic data from Mongolia, Siberia, and North China and argue that previously published apparent polar wander paths (APWPs) for North China and Siberia are insufficient to constrain the timing of MOO closure. Our new analysis incorporates newly published paleomagnetic data from North China and a refined geochronology for the key Siberian poles. We combine this with an updated global APWP incorporating large-scale Jurassic true polar wander and argue that the MOO was closed by the Middle Jurassic. This temporal shift is compatible with geology-based models. The Middle Jurassic reconstruction of Eurasia suggests that the East Asian blocks had become a quasi-rigid part of Pangea prior to breakup.