An assessment of the reliability of palaeointensity results obtained from the Cretaceous aged Suhongtu section, Inner Mongolia, China

摘要: Abstract Here we present microwave palaeointensity results from 89 sister samples the study of Zhu et al. [Zhu, R., Pan, Y., He, H., Qin, Ren, S., 2008. Palaeomagnetism and 40 Ar/ 39 Ar age a Cretaceous volcanic sequence, Inner Mongolia, China: implications for field variation during normal superchron. Phys. Earth Planet. Int., 169, 59–75] who carried out Thellier analysis as part their integrated palaeomagnetic dating lava Suhungtu section, China. Additionally, comprehensive rock magnetic investigation has been in order to determine mineralogy hence validity assuming that remanence is thermal remanent magnetisation (TRM). The are apparent high quality give flow mean estimates ranging 13 49 μT corresponding virtual dipole moment (VDM) 2.5 8.9 × 10 22  Am 2 , an overall VDM 5.5 ± 1.9 × 10 24 flows (aged 110.6 ± 0.1 Ma). When (using perpendicular applied method with partial (pT M RM) pT RM tail checks) compared those obtained (Coe version pTRM but not checks, heating argon atmosphere) differences seen at sample, unit level however, means spread consistent. Some discrepancy due differing sized sample sets inhomogeneity also interpreted be protocols, methodology, plus subjectivity interpretation. Considering only consistent within 20% remains. There substantial evidence progressive air experiments (both showing irreversible thermomagnetic behaviour) well looking under scanning electron microscope suggest maghaemite (albeit varying degrees) many samples. Alteration therefore occurred nature it likely will have affected degrees potentially causing underestimates palaeointensity. Maghaemite carrier where component remains after 580 °C loss acquisition capacity found on heating. No correlation was between estimated (microwave or datasets) amount temperature any parameter. This could reliable seems more than one factor (such protocol, interpretation, chemical (CRM) contamination geomagnetic field) influencing estimates. In attempt remove influence protocol methodology datasets were reduced consist mutually ( N  = 22). obvious again inferred contribution estimate. no clear biasing CRM (assuming simple relationship contribution) can thus major factor. Further studies however needed fully elucidate extent result each possible ultimately reliability rocks this type.