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Accumulation of the global paleomagnetic data, from both continental and oceanic plates, may suggest a true polar wander (TPW) event in Jurassic, with a rotation axis located in the present northwestern Africa, but no consensus has been reached regarding to the initiation, duration and velocity of the TPW. As one of the eastern Asian blocks, the north China block (NCB) is then located far from the rotation axis of the TPW and the plate convergence between Siberia and the Amur-NCB, known as the subduction in the Mesozoic Okhotsk-Baikal ocean, did exist. Paleogeographic changes observed of the eastern Asian blocks in Jurassic thus should contain the TPW component and plate moving component. To better estimate the influence of the TPW in the Eastern Asia blocks, we carried out a new paleomagnetic and precision U-Pb geochronological study on the middle Jurassic lavas in the NCB. Being profoundly different to the recent paleogeographic model (Yi et al., 2019, https://doi .org/10.1130/G46641.1) that suggest that the NCB experienced a large latitudinal displacement (monster-shift) responding to the TPW event between ~174 and ~157 Ma, we suggest that the NCB, as well as other blocks already connected with it, do not record any monster-shift between ~170 and ~160 Ma. The strata, ranging from 160 to 145 Ma, however, yield considerable paleomagnetic variations and need further investigation.

Fossil organisms of the Boreal Realm in the Tuva–Mongol Block (TMB) and Amuria Block (AMB) are commonly thought to have lived at mid to high latitudes during the Carboniferous Period; however, reliable paleomagnetic constraints have not been available previously to test this hypothesis. Here we report newly obtained combined paleomagnetic and geochronological results from the Upper Mississippian Gunbayan Formation in the AMB and the Lower Pennsylvanian Altan-Ovoo Formation in the TMB. Zircon U–Pb dating of tuff beds from the Gunbayan and Altan-Ovoo formations yield ages of 331.0 ± 2.7 and 315.5 ± 2.4 Ma, respectively. A total of 263 paleomagnetic specimens underwent stepwise thermal demagnetization. After removing the viscous remanent magnetizations of the recent geomagnetic field, stable high-temperature components (HTCs), carried by magnetite, were successfully acquired from 240 specimens. The HTCs of the Gunbayan Formation passed a fold test and a reversal test, and those of the Altan-Ovoo Formation passed a fold test, suggesting that they represent primary remanence magnetizations. We used the elongation/inclination method to test and correct for all the HTC directions of the clastic rocks of the studied formations. Their corresponding paleomagnetic poles are 46.0°N/320.0°E (A = 95 2.0 °) at ca. 330 Ma for the AMB and 43.5°N/355.9°E (A = 95 2.9 °) at ca. 315 Ma for the TMB. The updated paleomagnetic database indicates with certainty that both the TMB and the AMB were located in northern hemisphere low-latitude regions and close to the equator at ca. 330 Ma, suggesting that the Boreal Realm might have extended into the equatorial region at the onset of the large ice age of the Carboniferous. The paleobiogeographic characteristics and distribution of climate-sensitive lithologies indicate that this realm occupied a wide northern temperate belt during 330–315 Ma.

Jurassic witnessed two synchronous events on the Earth, named true polar wander (TPW) and closure of the Mongol–Okhotsk ocean (MOO) between Siberia and eastern Asian blocks. The paleogeographic change of the north China block (NCB) should thus include both TPW and plate tectonic components in Jurassic. We performed a new combined paleomagnetic and U–Pb geochronological study for Middle and Late Jurassic volcanic rocks from the northern NCB and obtained three new well-dated paleopoles: 82.7°N, 282.6°E, A 95 = 3.2 ° (ca. 160 Ma); 84.1°N, 228.9°E, A 95 = 6.6 ° (ca. 165 Ma); and 89.3°N, 216.8°E, dp/dm = 5.4°/7.1° (ca. 170 Ma). A positive untilting test indicates a pre-folding origin interpretation for the ca. 160 Ma pole. Quality of these poles is enforced by three positive conglomerate tests, the presence of magnetic reversals and secular variation analyses. Comparison of the apparent polar wander paths of Eurasia and the NCB suggests that the NCB accreted to Eurasia around 140 Ma. The NCB and its then connected blocks did not undergo any significant southward paleogeographic shift during Jurassic. In context of TPW, we estimate a net northward plate moving velocity at 0.50–0.75°/myr for the NCB in Jurassic. The long-term accumulation of MOO subducted slabs at the high paleolatitudes may have critically contributed to, or perhaps led to, the Jurassic TPW.

The Amuria block occupies the eastern part of the Central Asian Orogenic Belt between the Siberia craton and the North China block (NCB) and bears important information to understand the evolution of the MongolOkhotsk suture and the amalgamation of East Asia. However, the paleomagnetic database of Amuria remains very poor.