Characterizing the geomagnetic paleosecular variation at high latitudes in late Mesoproterozoic: new evidence from carbonate successions of the Jingeryu Formation in the North China craton

The dispersion of virtual geomagnetic poles (S parameter) at high latitudes in the Precambrian is still unclear due to a dearth of data, which hampers a well understanding of the geomagnetic paleosecular variation (PSV) behavior in Earth's history. Here we present new paleomagnetic and cyclostratigraphic results from late Mesoproterozoic carbonate successions of the Jingeryu Formation in the North China craton. A 29-m section was sampled for high-resolution paleomagnetic and magnetic susceptibility analyses at a scale of ~6 cm. The average sedimentation rate was estimated as ~0.8 cm/kyr based on cyclostratigraphic analysis, which was used for constructing an age model for the strata. For most samples subjected to stepwise thermal demagnetization, a high-temperature component (HTC) was isolated after removing a low-temperature component of viscous magnetic remanence acquired in recent geomagnetic fields. The HTC is characterized by steep inclinations, whose primary nature is bolstered by the presence of geomagnetic reversals. We quantified a series of S parameters using the paleomagnetic results from the Jingeryu Formation, calculated for every ~50-kyr interval, which enriched the PSV data in the latitude interval of ~45°-80°. Our new data show a consistency with the S-paleolatitude models (i.e., Model G fits) previously established based on paleomagnetic data from Proterozoic igneous rocks (Smirnov et al., 2011; Veikkolainen & Pesonen, 2014), demonstrating that Model G is a useful framework to gauge the geomagnetic PSV in the late Mesoproterozoic.

References

Smirnov, A. V., Tarduno, J. A., & Evans, D. A. D. (2011). Evolving core conditions ca. 2 billion years ago detected by paleosecular variation. Physics of the Earth and Planetary Interiors, 187, 225-231.

Veikkolainen, T., & Pesonen, L. J. (2014). Palaeosecular variation, field reversals and the stability of the geodynamo in the Precambrian. Geophysical Journal International, 199, 1515-1526.