Pangea is a complete supercontinent: paleomagnetic evidence from North China

Alfred Wegener proposed the idea of a supercontinent, which he called Pangea about one century ago. The idea led directly to the hypothesis of continental drift, which eventually evolved into the theory of plate tectonics. Pangea is traditionally represented by ~75% of continental crust in which the East Asian blocks (EABs) are typically omitted. Climate models developed using an outboard position of the East Asian blocks led to the hypothesis of a mega-monsoon.

Aiming to refine the paleogeography of Pangea, this study reports a new late Triassic paleopole for North China based on dykes and sills sampled from two localities that were ~500 km apart. Laser-ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) U-Pb dating on zircons selected from the sills yields a mean age of 224.4 ± 1.4 Ma. The characteristic remanent magnetizations isolated from the two localities are consistent and pass reversal and baked-contact tests suggesting a primary origin. The high-quality paleomagnetic pole positioned the EABs at 75.6° ± 6.8° N at ~220 Ma using Beijing as a reference site, which is in good agreement with the paleolatitude resolved from the apparent polar wander path of Eurasia. Along with the ages newly-reported from the “stitching pluton” that intruded the Mongol-Okhotsk suture, our study reveals a full amalgamation between the EABs and Pangea by ~220 Ma, indicating that Pangea comprises ~99% of available continental crust and was perhaps the largest of all known supercontinents.

The refined reconstruction of East Asia provides an opportunity to reevaluate the paleogeography and climatic patterns of Pangea. The climate-sensitive lithofacies in East Asia indicate a humid-temperate climate during the Late Triassic and Early Jurassic. The wet conditions were typically explained via a mega-monsoon model. However, according to our new reconstruction, much of the EABs are positioned above ~40° N (within the humid-temperate to subpolar humid zones) during the Late Triassic and early-Middle Jurassic. The humid-temperate conditions are therefore consistent with a zonal climate pattern. To better evaluate climatic patterns of Pangea from a global perspective, we further restore the climate-sensitive lithofacies of the Late Triassic according to our Pangea reconstruction. The distribution of lithofacies is compatible with a zonal climate when Pangea reached its maximum size and optimal equatorial symmetry for developing a monsoon climate, which obviates the need for the Pangean mega-monsoon hypothesis.