New paleomagnetic results from the Jingeryu Formation in the North China craton and their implications

Abstract

We present new rock magnetic and paleomagnetic results from late Mesoproterozoic carbonate successions of the Jingeryu Formation (Fm) in the northern North China craton (NCC). Rock magnetic experiments, including thermomagnetic susceptibility curves, isothermal remanent magnetization (IRM) and thermal demagnetization of three-axis IRM, carried out for representative samples from the Jingeryu Fm indicate that both hematite and magnetite are abundant in the purplish-red limestone in the lower part of strata and the magnetic carriers of the pale blue limestone in the upper part are magnetite grains. 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 supported by the presence of geomagnetic reversals. The similarities in paleomagnetic results and the correlatable lithologic sequence support that the Jingeryu Fm, the Nanfen Fm in the eastern Liaoning region in northeastern NCC and the Xinxing Fm in the Xuzhou region in southeastern NCC are correlative strata deposited in the polar region. Recently published radiogenic isotopic results constrain the depositional age of the Nanfen and Xinxing formations around ca. 1.1 Ga. Those high-latitude carbonate rocks widely distributed in the NCC predict an extraordinary climate condition around ca. 1.1 Ga.