Tonian paleomagnetic poles from South China are consistent with progressive plate tectonic motion over the North Pole: COMMENT

Tertiary paleomagnetism of North and South China and a reappraisal of late mesozoic paleomagnetic data from Eurasia: Implications for the cenozoic tectonic history of Asia

A high-quality mid-Neoproterozoic paleomagnetic pole from South China, with implications for ice ages and the breakup configuration of Rodinia

Tonian true polar wander events recorded by paleolatitudinal variations of South China and its Southern Hemispheric position in Rodinia

A pan-latitudinal Rodinia in the Tonian true polar wander frame

The paleogeographic relationship between South China and Australia during the Ordovician is important for understanding the configuration of South China in Gondwana. However, high‐quality Ordovician paleomagnetic results for the Yangtze Block are scarce. Here we report the results of a new paleomagnetic study of the Late Ordovician limestones of Wangcang County in the northern Yangtze Block, performed in order to constrain the paleoposition of South China. Two magnetic components were isolated by detailed stepwise thermal demagnetization. The low‐temperature component falls close to the local current Earth's field direction. The site‐mean direction obtained from the high‐temperature component (HTC) carried by magnetite is D/I = 132.6°/−35.2° (α95 = 3.6°) after bedding correction, yielding a paleomagnetic pole at 45.8°S, 191.3°E (dp = 2.4°, dm = 4.2°). The HTC direction passed reversal and fold tests, and its corresponding pole differs from the available paleomagnetic poles since the Silurian of the South China Block. These results suggest that the remanent magnetization was probably acquired during the earliest stage of sedimentation. The high‐temperature component yields a paleolatitude of 19.5°S, implying that the Yangtze Block was at tropic latitudes during the Late Ordovician. These new and reliable paleomagnetic results bridge the Ordovician data gap and favor the proximity between South China and Australia during the Late Ordovician.

New paleomagnetic results from the Ediacaran Doushantuo Formation in South China and their paleogeographic implications

High northern geomagnetic field behavior and new constraints on the Gilsá event: Paleomagnetic and 40Ar/39Ar results of ∼0.5–3.1 Ma basalts from Jökuldalur, Iceland

New and revised set of Cretaceous paleomagnetic poles from Hong Kong: implications for the development of southeast China

A revised paleomagnetic pole from the mid-Neoproterozoic Liantuo Formation in the Yangtze block and its paleogeographic implications

In order to better constrain the paleogeographic evolution of south China we measured Sm‐Nd and Rb‐Sr isotopic compositions for 23 Mesozoic granites that crop out throughout the area. Tightly grouped neodymium depleted mantle model ages (1.4 ± 0.3 Ga) suggest the region is underlain by relatively homogeneous Proterozoic crust and fail to define crustal provinces. Neither the isotopic nor geologic data suggest that a Mesozoic suture exists. However, granites possessing anomalously high Sm (>8 ppm) and Nd (>45 ppm) concentrations, relatively high initial epsilon neodymium (−4 to −8), and high but variable initial87Sr/86Sr (0.759 to 0.713) form a northeast trending zone that coincides with two prominent Mesozoic basins. Southeast of the zone lie the majority of Mesozoic intrusives and Upper Triassic to Lower Cretaceous extensional basins found in south China. Mesozoic paleomagnetic poles are well clustered northwest of the zone. Pre‐Cretaceous poles southeast of it are discordant with respect to those from the northwest. The only recognized tectonostratigraphic terrane in south China lies southeast of the zone. The terrane is bordered by a northeast trending sinistral fault that was active in the Mesozoic. Other faults in south China have similar attitudes, ages, and sense of shear. Together, the observations suggest that the Mesozoic tectonic regime in south China consisted of strike‐slip activity plus concomitant rifting as terranes or fragments of similar crust were transported north along sinistral faults. The zone, defined by the granites enriched in Nd and Sm, demarcates displaced terranes to the southeast from relatively stable land to the northwest.

Paleomagnetism and rock magnetic cyclostratigraphy of the Ediacaran Doushantuo Formation, South China: Constraints on the remagnetization mechanism and the encoding process of Milankovitch cycles

The link between geomagnetic excursions and climate is an exciting but still unresolved topic. The idea reposes on the increased solar and cosmic ray radiation in response to the weakened magnetic field during the transitional fields accompanying a geomagnetic reversal or excursion. However, a direct climate response to the variations of the Earth magnetic field is not yet demonstrated in the geological record. A major limitation resides in the fact that paleomagnetic data are usually extracted from igneous or sedimentary rocks, which usually provide no or poor-quality paleoclimate information. Recent advances in speleothem magnetism fill this gap and open a new door to investigate the link between climate and the variation of the Earth magnetic field in the same geological archive. Here we document absolute paleotemperatures based on water isotopes in fluid inclusions from a Portuguese stalagmite that recorded the Laschamps geomagnetic excursion (~42 kyrs). The stalagmite was dated by radiocarbon method. Paleomagnetic data show the complete record of the Laschamps geomagnetic excursion, with paleomagnetic poles moving from the north pole down to the south pole and returning to the original position in ~3000 kyrs. Paleointensity data show a weakened magnetic field associated with the migration of the paleomagnetic pole. Absolute paleotemperatures were calculated using the fluid inclusion hydrogen isotope (d2H) and the calcite-water isotope fractionation paleothermometer on 19 samples encompassing the Laschamps event. The data show increased absolute temperatures just before and during the Laschamps. However, a strong correlation is noted between the absolute temperature calculated here and the oxygen isotope composition of the NGRIP ice core. Although the relation between paleotemperatures and the Laschamps event is not yet fully demonstrated in this case, the combination of paleomagnetic techniques coupled to isotope composition in speleothems offers new and promising perspectives to investigate the relationship between climate and the Earth magnetic field. This project is funded by Portuguese Fundação para a Ciência e Tecnologia, FCT, I.P./MCTES through national funds (PIDDAC): UID/50019/2025, UIDB/50019/2020 (https://doi.org/10.54499/UIDB/50019/2020), LA/P/0068/2020 (https://doi.org/10.54499/LA/P/0068/2020), and PTDC/CTA-GEO/0125/2021.

In order to study the motion of the Pacific plate with respect to the spin axis during the Cenozoic and Upper Cretaceous we combined an analysis of the distribution of pelagic sediments on the sea floor with paleomagnetic data collected on the Pacific plate. The facies distribution of sediments is used to determine the time when an equatorial crossing took place at as many sites as possible. By combining these two independent data sets, bounds can be placed on the relative motion of the ‘hot spots’ with respect to the spin axis. The data strongly suggest that the Hawaiian hot spot has remained close to its present latitude for the last 70 m.y. with an uncertainty in the rate of latitudinal motion of about 1 cm/yr. A set of continental paleomagnetic data was selected on the basis of the number of samples used, the degree of secondary demagnetization, the uncertainty of the mean direction of magnetization, and the tectonic stability of the region. These data are used to obtain independently the apparent polar wander curve of the Pacific plate. If the plates were rigid and the finite rotations were not grossly in error, reliable continental paleomagnetic poles rotated relative to the Pacific plate would yield a pole path consistent with the sediment facies data and with Pacific paleomagnetic data. Whereas the data from the Pacific plate indicate a latitudinal motion of almost 30° during the last 70 m.y., the rotated paleomagnetic poles from the continents cluster around the present‐day north pole and require essentially no latitudinal displacement of the plate during this same period of time. Several hypotheses are considered to explain this large discrepancy: a nondipolar behavior of the paleomagnetic field, insufficient quality of the existing Cenozoic paleomagnetic catalogue, or a large amount of internal deformation in the Antarctic or Pacific plate from the Upper Cretaceous to the Lower Oligocene.

A true polar wander path is presented for the past 180 Ma tracing the relative motion between the hotspot framework and the geomagnetic poles deduced from worldwide paleomagnetic data. A relative displacement of 22°±10° is observed. The motion between the two reference frames has not been smooth. Episodes of rapid motion, on the order of 80–100 mm/yr, include the present, 65–50 Ma, 115–85 Ma, and 180–160 Ma. Periods of slow or little polar motion, less than 20 mm/yr, are observed at 50–5 Ma and 160–115 Ma. The effect of plate motions is removed using Morgan's plate motion model A19. This model is tied to a hotspot reference frame assumed to be fixed in the mantle. The rotated paleopoles are grouped by ages and then averaged. They are found to cluster about points distinct from the north pole as defined by the hotspots. These points trace out a path of motion between the rotation axis and the hotspots or mantle. This is interpreted as a shifting of the entire earth in response to a change in the principal axes of the moment of inertia of the mantle. Paleomagnetic poles of the past 7 m.y. are examined independently. This eliminates a dependence on the fixed hotspot hypothesis, since plate motions are essentially negligible for this time span. There is a deviation of 5°±2° between the present geographic north pole and the average of the paleopoles at 5 Ma. This is too great to attribute to plate motion. Interpreted as true polar wander, the rate of this polar motion is about 1°/m.y. Astronomical measurements for the past 80 years have recorded actual motion of the earth's rotational axis up to 1°/m.y. in the direction of eastern Canada. This agrees in rate with paleomagnetic polar motion of the past 7 m.y. and in both rate and direction for the past 2 m.y.

The Arctic air mass is the cold, dry body of air slowly moving eastwards around the North Pole in the northern hemisphere. Its southern boundary consists of four planetary waves known as the Rossby waves that mark the interface with subtropical air bringing heat polewards. The Arctic air mass is constantly being modified by the addition of heat and moisture over the oceans, as well as by winter cooling over the land masses due to limited incoming solar radiation and constant reradiation of heat into the atmosphere. The coldest air in winter is located over northeastern Siberia and moves east, cooling Canada. Warm ocean currents add large quantities of heat to the air mass moving over them, but without this addition of heat, the Arctic air mass becomes significantly colder. Research in Tibet and Northeast Asia on depression of sea level shows that during the Late Wisconsin cold event (65–10 ka B.P.), vast quantities of sea water were sequestered on land primarily as ice sheets, exposing the sea bed in the Bering Strait from 50–10 ka B.P. together with the bottom of the South China Sea between 30–20 ka B.P.. The East China Monsoon failed to reach Tibet and much of Northeast China, resulting in severe cooling of northeast Siberia and northern Tibet. This, in turn, caused severe cooling in eastern Canada together with the development of a vast, predominantly cold-based ice sheet. As the sea levels started to rise (about 19 ka B.P.), the East China Monsoon slowly redeveloped and a gradual warming took place on both continents. However, along the west side of the North American Cordillera, the Late Wisconsin glaciation only began in 29 ka B.P. but continued along the west coast until about 10 ka B.P. This paper explores the relationship of the Late Wisconsin history on the two continents, together with the mechanisms causing the landforms and climatic differences. Finally, the probable effects of these climatic changes on the early peopling of North America are discussed.