NJU School of Earth Sciences and Engineering professor Yong-Xiang Li’s research article “Salient Changes of Earth's Magnetic Field Toward the End of Cretaceous Normal Superchron (CNS)” was recently selected by AGU for featuring as an Editor’s Highlight, and this has been published on AGU’s science news magazine Eos.org: https://eos.org/editor-highlights/the-not-so-quiet-cretaceous-quiet-zone. Fewer than 2 per cent of papers are selected to be featured in this way. AGU is a global community supporting more than half a million advocates and professionals in the Earth and space sciences. AGU publishes 24 peer reviewed journals in open-access and subscription models.
Earth’s magnetic field exhibits an almost constant normal polarity from ~121 million years ago (Ma) to 84 Ma in mid-Cretaceous. This ~37 million-year interval is known as Cretaceous Normal Superchron (CNS) or the Cretaceous Quiet Zone. The intensity of Earth’s magnetic field during CNS was thought to be persistently strong and stable based on estimates from snapshot recordings of igneous rocks and modeling work. NJU professor Yong-Xiang Li, PhD student Xinyu Liu, and Prof. Carl Richter from University of Louisiana at Lafayette, USA jointly carried out a study investigating changes in Earth’s magnetic field strength (paleointensity) during CNS and obtained a 6 million-year, high-resolution, nearly continuous relative paleointensity (RPI) record for the late CNS. The new RPI record shows considerable variations in geomagnetic field intensity, rather than being “strong and stable” as previously thought, that are also consistent with those shown in the marine magnetic anomaly (MMA) data. Integrated analysis reveals a strong and highly variable geomagnetic field in the middle CNS but a weak and stable field at its beginning and ending.
The Eos Highlight points out: (1) the findings of this study suggest that the geodynamo, by which Earth’s magnetic field is generated, was more dynamic than previously thought and may provide clues concerning the origin, development and termination of geomagnetic superchrons; (2) this study robustly documents a much more variable geomagnetic field during the Cretaceous Normal Superchron than acknowledged up to now, an important result that enables benchmarking geodynamo simulations for this time interval.
This research was published in AGU’s Journal of Geophysical Research-Solid Earth (Nature-Index Journal) on April 15, 2024. This study was financially supported by National Natural Science Foundation of China and International Ocean Discovery Program (IODP)-China.
Article information：
Xinyu Liu, Yong-Xiang Li*, Carl Richter (2024). Salient changes of Earth's magnetic field toward the end of Cretaceous Normal Superchron (CNS). Journal of Geophysical Research: Solid Earth, 129, e2023JB028104. https://doi.org/10.1029/2023JB028104
