Haiyan Li

The closure of the Meso‐Tethys Ocean is crucial to understanding the global evolution of the Tibetan Plateau prior to the India‐Asia collision and its influence on the environment and climate. Nonetheless, large uncertainties exist regarding the process due to the scarcity of reliable Late Jurassic paleomagnetic results. Here we present a combined paleomagnetic and geochronologic study on the ca. 147 Ma Zenong Group volcanic rocks in the westernmost Lhasa terrane. We obtained a well‐dated high‐quality paleopole at 63.0°N, 304.9°E with N = 20 sites, K = 29.9, and A ₉₅ = 6.1°, yielding a paleolatitude of 11.9 ± 6.1°N for the sampling area. The primary origin of the magnetization is supported by positive fold and reversal tests, with the statistical distribution consistent with the expected geomagnetic paleosecular variation. This new paleomagnetic result permits reconstructing the northward trajectory of the Lhasa terrane from the Southern Hemispherical paleolatitude toward Eurasia. Direct comparison with the pre‐collisional paleolatitude of the Qiangtang terrane demonstrates that the western part of the Meso‐Tethys Ocean remained open at ca. 147 Ma. Furthermore, by integrating our results with other reliable Late Triassic to Early Cretaceous paleomagnetic data sets from the Lhasa and Qiangtang terranes, together with regional geological evidence, the comparative results reveal that the final closure of the Meso‐Tethys Ocean occurred during ca. 140–130 Ma in the western part.

The drift history of the Tethyan Himalaya provides key constraints on the India‐Asia collision, Himalayan‐Tibetan orogenesis, and associated global climate change. Here we present rock magnetic, petrographic, geochronologic, and paleomagnetic results of the Bolinxiala Formation limestones in the western Tethyan Himalaya. In situ calcite U‐Pb dating and biostratigraphy indicate that the Bolinxiala Formation limestones were formed during the Early Cretaceous (∼125–100 Ma), not Middle Jurassic as previously thought. The site‐mean direction for the 23 sites is D _g = 23.3°, I _g = +10.0°, k _g = 40.1 and α ₉₅ = 4.8° in situ and D _s = 20.8°, I _s = +19.0°, k _s = 67.2 and α ₉₅ = 3.7° after tilt‐correction, yielding a paleomagnetic pole position at 61.6°N, 212.9°E with A ₉₅ = 2.7°, corresponding to a paleolatitude of 10.3° ± 2.7°N. A positive fold test indicates a prefolding origin. When compared with reliable Cretaceous–Eocene paleopoles from the western Tethyan Himalaya, we suggest that the Bolinxiala Formation limestones likely underwent remagnetization during ∼54–49 Ma. Petrologic evidence, including the presence of framboidal oxides derived from sulfides (primarily pyrite) and calcite veins, supports chemical remanent magnetization as the primary mechanism responsible for the remagnetization. Our new results, combined with reliable Cretaceous paleomagnetic data from the western Lhasa terrane, indicate that the western part of the India‐Asia collision occurred no later than ∼54–49 Ma.

Disentangling short‐duration (≤10 Ma) true polar wander (TPW) events in the Precambrian presents a significant challenge, necessitating the acquisition of high‐resolution and ‐quality paleomagnetic data and well‐determined age relations. This study reports new paleomagnetic results from carbonate sequences of the Jingeryu Formation in the North China craton (NCC), which correlate with the lower part of the ca. 1,100 Ma Nanfen Formation. Detailed rock magnetic examination, the presence of magnetic reversals and the distinguishable characteristic remanent magnetization isolated from different parts of the section support the interpretation that the remanence is primary. Integrated with cyclostratigraphic age models, these quasi‐continuous data document a rapid paleolatitudinal drift of the NCC from mid‐to high‐latitudes at ∼28 cm/yr. The average pole shift rate of ∼5.4°/Ma during deposition of the Jingeryu Formation represents a TPW event preceding the ca. 1,109–1,083 Ma volcanism within the North American Midcontinent Rift. This newly identified short‐duration TPW episode (∼9.3 Ma duration) likely operated independently from the long‐term (ca. 1,165–1,015 Ma) inertial interchange TPW. We interpret this rapid TPW as Earth's rotational response to transient solid Earth mass redistribution during the Nuna–Rodinia supercontinent transition. Mass anomalies arising from widely distributed mafic dike swarms, subduction‐related magmatism, and accretionary orogenies may have contributed to this rapid TPW event. Critically, validating this global event requires more high‐resolution paleomagnetic records from temporally precisely coeval sections in other continental blocks.

The boundary between wet and arid climate zones in the Tethys Ocean remains challenging to trace, complicating our understanding of global aridification pattern during the Late Carboniferous to Early Permian transition. The North China Block (NCB), situated in the Tethys Ocean, underwent a transition from humid to arid climate during the Early Permian, providing a rare opportunity to trace this climate boundary across this region. Here, we present paleomagnetic evidence indicating that the NCB underwent rapid northward drift between 290 and 281 million years ago. The NCB’s movement from a tropical wet to a subtropical arid zone corresponds to a lithological change from coal-bearing to red-bed deposits, demonstrating tectonic drift into a subtropical arid zone as the main driver of aridification in the NCB during this period. This drift also delineates the wet–dry boundary over the Tethys Ocean, consistent with modern climatic zonation patterns.

To refine the postcollisional extrusion and convergence history of the southeastern Tibetan Plateau, we report a quality paleomagnetic data set from Upper Cretaceous redbeds of the eastern Qiangtang Terrane (QT), where is situated at the front edge of eastern Himalayan Syntaxis. The 32 site‐mean directions provide a mean pole at 75.4°N, 176.8°E (A₉₅ = 2.4°) and a paleolatitude of 31.8 ± 2.4°N for the Mangkang area. Comparison with reliable Late Cretaceous paleomagnetic data from the eastern QT and East Asia indicates that the eastern QT experienced a southward extrusion of 940 ± 310 km after the Late Cretaceous. Comparing Late Cretaceous paleolatitudes estimated from the eastern QT and Lhasa terrane (LT) reveals a paleolatitude difference of 2,390 ± 620 km. Such a great latitudinal convergence can be attributed to the fact that some continental terranes originally located between the eastern LT and QT were laterally extruded after the Late Cretaceous.

True polar wander (TPW) or equatorial dipole (ED) field hypothesis have the potential to decipher the Ediacaran paleomagnetic enigma, based on the fast apparent polar wander (APW) rate revealed by the orthogonal directional groups. However, determining the final solution is challenging, as the conservatively estimated APW rates for both hypotheses are consistent given current chronological constraints. A precise APW rate is thus urgently needed. Fortunately, two distinct poles and a transition zone were identified from the astronomical calibrated Member 3 of the Doushantuo Formation in the Zhengjiatang section, South China. The APW rate was precisely constrained to be 243 ± 17°/Myr, an extremely fast rate which excludes an origin of fast plate motion or TPW. Based on the current global Ediacaran to Early Cambrian paleomagnetic data, the ED field at ca. 596–570 Ma is suggested to be responsible for the rapid directional change.

The identification of the Grenvillian‐age ophiolite suites in the Yangtze block in recent years suggested that the northern Yangtze subblock (NYB) and the southern Yangtze subblock (SYB) were once separated by an ocean in late Mesoproterozoic. Although some paleogeographic models advocated the Pre‐Grenvillian connections between the south China blocks and Laurentia, none of them has been paleomagnetically tested. Here we report the new paleomagnetic results obtained from the ∼1,270 Ma purplish‐red muddy dolomite beds of the Luanshigou Formation, Shennongjia Group, NYB, providing new constraints for reconstructing the paleogeographic positions of the south China blocks in late Mesoproterozoic. A total of 447 samples underwent stepwise thermal demagnetization. Two components were identified. The low‐temperature component is interpreted as the recent viscous remnant magnetization. The high‐temperature component was obtained from 64 samples below 580°C and from 177 samples below 690°C, directed northeast‐up or southwest‐down, antipodally, positioning the paleomagnetic pole at 18.5°S, 74.4°E (dm/dp = 2.5/1.6°). Rock magnetic results demonstrate that the magnetic carriers in purplish‐red dolomite and pale‐pink dolomite are predominated by hematite and magnetite, respectively. The data quality is supported by an inverse baked contact test, a B‐class reversal test, and the paleomagnetic pole is distinct from any younger poles of the region. Based on the paleomagnetic results, aided by geological evidence, we propose a reconstruction in which the NYB was juxtaposed to southwestern Laurentia in the late Mesoproterozoic and suggest that the late Mesoproterozoic Miaowan‐Shimian ophiolite zone in the Yangtze block was likely an extension of the Grenville belt of Laurentia.

The timing of formation of the Hegenshan suture is crucial to understanding the evolution of the Central Asian Orogenic Belt (CAOB). Here we present a well‐dated paleomagnetic pole (103 samples from 15 sites, 36.7°N/29.2°E, A₉₅ = 3.3°) that passed a positive fold test, a reversal test, and a conglomerate test from the ∼250 Ma upper Gunbayn Formation andesites in the southeastern Mongolia Block (MOB). The high‐quality paleomagnetic database may demonstrate that the MOB drifted rapidly southward and collided with the Xilinhot–Songliao Block between 256 and 250 Ma, resulting in the closure of the Hegenshan Ocean at ∼250 Ma. The Hegenshan suture and the Solonker suture were formed almost simultaneously and marked the final closure of the Paleo‐Asian Ocean.

The drift history of the Lhasa terrane is crucial for understanding the tectonic evolution of Tethyan Oceans and Jurassic true polar wander. However, high‐quality Middle Jurassic paleomagnetic data from the Lhasa terrane are limited in number. Here we report a combined paleomagnetic and geochronologic study on the Yeba Formation volcanic rocks, dated at ∼170 Ma, from the Lhasa terrane. Robust field and reversal tests indicate that the characteristic remanent magnetizations are primary. Our results provide a reliable Middle Jurassic (∼170 Ma) paleopole at 29.8°N, 180.7°E with A ₉₅ = 5.7° and a paleolatitude of 14.4 ± 5.7°N for the Lhasa area. Compared with previous paleomagnetic and geologic evidence, we propose that the Meso‐Tethys Ocean probably began to close in the eastern part at ∼168 Ma and that the Lhasa terrane underwent a ∼2,900 km southward “monster shift” during the Late Jurassic.

The continuous sedimentary cores recovered at the International Ocean Discovery Program (IODP) Site U1505, Expedition 368, provide an opportunity for paleoceanography and paleoclimate reconstruction in the continental margin of the northern South China Sea (SCS). In this study, we conducted detailed rock‐ and paleomagnetic studies on 420 discrete samples from the top ∼200 m of the synthetic records of Holes U1505C and U1505D. Rock magnetic analyses indicate that low‐coercivity pseudosingle domain magnetite dominates as the primary ferromagnetic mineral of Site U1505. The magnetostratigraphic age model was constructed by correlating the interpreted polarity sequence with the Geomagnetic Polarity Time Scale 2020 with the constraints of the biostratigraphic data and the distribution probability of the age of each polarity zone provided by a Dynamic Time Warping algorithm. The Milankovitch cycles of the short eccentricity, obliquity, and precession cycles were identified in the magnetic susceptibility (MS) and natural gamma radiation (NGR) series based on paleomagnetic results. We established an ∼9 Myr high‐resolution astronomical time scale by tuning the MS and NGR records to the global oxygen isotope curves, the obliquity, and the eccentricity curves of the La2004 astronomical solution. Our new age model reveals detailed sedimentation rate variations and a ∼500 kyr hiatus across the Brunhes‐Matuyama boundary related to local tectonic activity. These results lay the foundation for understanding the paleoceanography and paleoclimate evolution of the SCS.