Paleomagnetic Constraints on the Rapid Plate Shift of North China Block During the Jurassic From ∼155 Ma Dykes and Sills.

A large‐scale apparent polar wander occurred during the Jurassic interval, which is interpreted as true polar wander (TPW). As the motion is nearly orthogonal to the TPW axis, the North China Block (NCB) experienced the largest latitudinal and environmental changes and provides unique constraints on Jurassic TPW. However, due to the lack and uneven quality of paleomagnetic data, TPW records in North China are controversial. Here, we report a new paleomagnetic pole (80.8°N, 13.0°E, A95 = 7.4°) from the late Jurassic sills and dykes that intrude the Nandaling and Xiahuayuan formations in the NCB. The new pole places the NCB at 36.8° ± 7.4°N at 155 ± 3.4 Ma, using Beijing as the reference site. Combined with the reliable Jurassic poles, our study reveals a large, steady southward shift of 37.3° ± 7.2° for the NCB during the Middle and Late Jurassic, and reflects a component of TPW. The position of ∼155 Ma pole also supports significant TPW prior to ∼160 Ma and agrees with proposals attributing the diachronous 165–155 Ma aridification across the Eastern Asian blocks. Plain Language Summary: True polar wander (TPW) refers to the rotation of a planet's upper solid shell relative to the spin axis, which helps stabilize its rotation and may result in rapid plate shift and environmental change. A large‐scale TPW occurred in the Jurassic but the configuration of which is controversial. Due to its unique location, North China provides unique constraints on Jurassic TPW, including paleolatitudinal, rotational and facies changes. Here we report new paleomagnetic data from a suite of sills and dykes in the North China Block (NCB). Combined with the available Jurassic paleomagnetic data, our study reveals a large, steady southward shift of ∼4,000 km for NCB between ∼174 and 147 Ma, and reflects a component of a proposed monster Jurassic TPW. The plate motion of the NCB also supports significant TPW prior to ∼160 Ma, that is compatible with the diachronous aridification through East Asia between ∼165 and 155 Ma. Key Points: A new paleopole reported from the late Jurassic sills and dykes positions the North China Block (NCB) at ∼37°N at ∼155 MaThe NCB experienced a huge, steady southward shift of ∼4,000 km during ∼174–147 Ma, reflecting a component of true polar wander (TPW)The plate shift of the NCB supports considerable TPW prior to ∼160 Ma, which is compatible with the ∼165–155 Ma aridification across East Asia [ABSTRACT FROM AUTHOR]