Paleointensities from a Cretaceous basalt platform in Inner Mongolia, northeastern China

Thellier’s paleointensity experiments were carried out using Cretaceous basalts of 90 Ma which were taken from a basalt platform in Inner Mongolia, northeastern China. Hysteresis parameters indicate that bulk grain size is PSD in all samples. JS–T curves indicate that the main magnetic mineral is titanomagnetite with Curie temperature (TC) of 200–350 °C with minor phases of higher TC which is known from the long tails continuing to the TC of magnetite. Samples often undergo severe chemical alteration on heating, resulting in a decrease of TRM capacity over the temperature range of 300–350 °C. Nevertheless, successful results were obtained from 47% of the total of 30 samples for the temperature steps lower than this critical point. Combining two results from possible identical flows, four paleointensities were obtained, ranging from 10 to 36 μT, which corresponds to a virtual dipole moment (VDM) of (1.8–6.0)×1022 Am2. These results support a low dipole moment during the later period of the Cretaceous long normal superchron (LNS).