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- Title
Late Cambrian geomagnetic instability after the onset of inner core nucleation.
- Authors
Li, Yong-Xiang; Tarduno, John A.; Jiao, Wenjun; Liu, Xinyu; Peng, Shanchi; Xu, Shihua; Yang, Aihua; Yang, Zhenyu
- Abstract
The Ediacaran Period marks a pivotal time in geodynamo evolution when the geomagnetic field is thought to approach the weak state where kinetic energy exceeds magnetic energy, as manifested by an extremely high frequency of polarity reversals, high secular variation, and an ultralow dipole field strength. However, how the geodynamo transitioned from this state into one with more stable field behavior is unknown. Here, we address this issue through a high-resolution magnetostratigraphic investigation of the ~494.5 million-year-old Jiangshanian Global Standard Stratotype and Point (GSSP) section in South China. Our paleomagnetic results document zones with rapid reversals, stable polarity and a ~80 thousand-year-long interval without a geocentric axial dipole field. From these changes, we suggest that for most of the Cambrian, the solid inner core had not yet grown to a size sufficiently large to stabilize the geodynamo. This unusual field behavior can explain paleomagnetic data used to define paradoxical true polar wander, supporting instead the rotational stability of the solid Earth during the great radiation of life in the Cambrian. An 80 thousand-year-long period of extreme non-geocentric dipole magnetic fields is recorded in Late Cambrian carbonate rocks of South China, suggesting that 495 million years ago Earth's inner core had not grown large enough to stabilize the dynamo.
- Subjects
CHINA; GEOMAGNETISM; EARTH'S core; POLAR wandering; MAGNETIC dipoles; CARBONATE rocks; CAMBRIAN explosion (Evolution)
- Publication
Nature Communications, 2023, Vol 14, Issue 1, p1
- ISSN
2041-1723
- Publication type
Article
- DOI
10.1038/s41467-023-40309-7