Abstract A complexity is emphasized in the distribution of French archaeomagnetic directions during the thirteenth and the fourteenth centuries AD. Data uncertainties, and the smoothing introduced when estimating an average secular variation curve, prevent scrutiny of the very nature of this complexity. It might correspond to a directional yaw, the nature of which would be compatible with the recent geomagnetic field evolution as traced by the gufm1 model. In order to emphasize this indeterminacy, a reference secular variation curve was constructed for dates between AD 1000 and 1500, including the yaw in question, and synthetic databases that mimic the accuracy and density characteristics of the true French archaeomagnetic database were considered for some of these. The synthetic curves hence obtained show that the dating accuracy of archaeomagnetic data is the crucial parameter for constructing a detailed secular variation path. The significant impact of the experimental data accuracy is also illustrated. Even more crucial is the fact that the precision of the data dating required to describe the directional variability over the century timescale largely exceeds the precision of the archaeological dates available for the structures generally studied. This highlights the intrinsic limitation of archaeomagnetism for regional reconstruction of century-scale geomagnetic field variations.

Abstract Twenty magnetostratigraphic profiles from IODP (International Oceanic Drilling Project) sediment cores distributed on the Earth's surface allowed the scatter of virtual geomagnetic poles (VGPs) during Brunhes–Matuyama times to be examined. We identified two groups of recording sites which give different paths for the VGPs during a time interval of about 1.1 myr. Calculations of the VGP velocities and accelerations, as well as the corresponding azimuths, resulted in mean/median values like those observed for recent times. No significant differences were observed during the ‘stable’ and transitional fields. The acceleration azimuths show variations from north–south to east–west depending on the field state: normal/reversed or transitional. Despite the uncertainties in the magnetization of the sediments (overprints and/or low-resolution records), we demonstrate that the use of this database is valid for obtaining kinematic parameters of the geomagnetic field when analysed on a statistical basis.

The Mesozoic and Paleogene pelagic carbonate rocks of the Northern Apennines have proved to be a fertile source for paleomagnetic research. Investigations of the magnetic properties of the Scaglia limestones illuminated the processes by which they were magnetized. Their directions of remanent magnetization contributed to an understanding of the geodynamic history of Adria as a promontory of the African plate and have been used to refine the Mesozoic part of the African polar wander path. Magnetic stratigraphy in the Umbrian sequence and in similar facies in the southern Alps has established an independent record of geomagnetic polarity history since the Middle Jurassic. Correlation with the record derived from interpretation of oceanic magnetic anomalies mutually confirmed the global nature of the polarity history. This enabled the dating of plate motions and the development of a geomagnetic polarity time scale for the late Mesozoic and Cenozoic.

We present a comprehensive study of one of the key targets of the Sikhote-Alin orogen—Early Cretaceous rocks in the Kiselevka block of the Kiselevka-Manoma tectono-stratigraphic terrane. The characteristic component of natural remanent magnetization (NRM) for these rocks was isolated, and the fold test was positive (Dec = 275.8°, Inc = −33.8°, K = 33.3. α 95 = 8.0°). The paleolatitude along which rocks of the block were forming in the Early Cretaceous was defined by the direction of this component (paleolatitude 18°N ± 5°N) as well as coordinates of the paleomagnetic pole (Plat = 18.6°, Plong = 222.4°, with semi-axis of the ellipse of confidence limit dp = 5.2° and dm = 9.1° of the Kiselevka block. The geochemical composition of volcanic rocks in the block suggests that they formed in a within-plate oceanic environment like volcanic rocks of the Hawaii hotspot. Three paleoreconstructions were developed based on the newly received and published data, in accordance with which the Kiselevka block: (1) in the range of 135–105 Ma was moving on the Izanagi plate northwestward at a rate of 15–20 cm/yr up to the eastern edge of Eurasia, thus covering over 5000 km; and (2) in the range of 105–70 Ma was moving northward along the Eurasian transform margin within the accretionary complex fragment at a rate of 4–5 cm/yr to its current position (Lower Amur) as part of the Sikhote-Alin orogen.

The eruptive history of the Shatsky Rise, a large oceanic plateau in the northwestern Pacific Ocean, is poorly understood. Although it has been concluded that the Shatsky Rise volcanic edifices erupted rapidly, there are few solid chronological data to support this conclusion. Similarly, the Shatsky Rise is thought to have formed near the equator, but paleolatitude data from the plateau are few, making it difficult to assess its plate tectonic drift with time. To understand the formation history of this oceanic plateau, paleomagnetic measurements were conducted on a total of 362 basaltic lava samples cored from the Shatsky Rise at 4 sites (U1346, U1347, U1349, and U1350) during Integrated Ocean Drilling Program Expedition 324. Examining changes in paleomagnetic inclinations, we gain a better understanding of eruptive rates by comparison of observed shifts in inclination with expected paleosecular variation. At three sites (U1346, U1347, and U1349) little change in paleomagnetic directions was observed, implying that the cored sections were mostly erupted rapidly over periods of <~100–200 yr. Only Site U1350 displayed directional changes consistent with significant paleosecular variation, implying emplacement over a period of ~1000 yr. The paleomagnetic data are consistent with the idea that the Shatsky Rise igneous sections were mostly emplaced rapidly, but there were some time gaps and some fl ank locations built up more slowly. Because paleosecular variation was inadequately sampled at all the Shatsky Rise sites, paleolatitudes have large uncertainties, and because of the equatorial location, magnetic polarity is also uncertain. All sites yield low paleolatitudes and indicate that the Shatsky Rise stayed near the equator during its formation. Given that the locus of magmatism moved northward relative to the Pacific plate while staying near the equator, the Pacific plate must have drifted southward relative to the spin axis during the emplacement of the plateau.