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

Abstract

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.