Revised Onset Age of Magnetochron M0r: Chronostratigraphic and Geologic Implications

Youjuan Li, Huafeng Qin, Brian R. Jicha, Magdalena H. Huyskens, Corey J. Wall, Robin B. Trayler, Qing-Zhu Yin, Mark Schmitz, Yongxin Pan, Chenglong Deng, Brad S. Singer, Huaiyu He, Rixiang Zhu

Research output: Contribution to journalArticlepeer-review

Abstract

The timing of the onset of magnetochron M0r and its duration are disputed, reflecting both a limited set of radioisotopic dates and uncertain magnetostratigraphic correlations. We present a chronostratigraphic framework for a reversed polarity interval based on two chronometers ( 40 Ar/ 39 Ar, U-Pb) and newly published paleomagnetic data from the Qingshan Group, Jiaolai Basin, China. Bayesian modeling of U-Pb zircon and 40 Ar/ 39 Ar sanidine dates suggests a minimum duration of 540 ± 37 k.y. (95% credible interval) for the reversed polarity interval. These findings are compatible with an astrochronologic age model for M-sequence seafloor magnetic anomalies, indicating that the reversely magnetized sediments correspond to magnetochron M0r rather than the shorter chron “M-1r.” Integration of U-Pb and 40 Ar/ 39 Ar ages constrains the onset of M0r to 120.29 ± 0.09 Ma, which is ~1 m.y. younger than that inferred in the current geologic time scale (GTS 2020). This finding also implies that the Cretaceous normal superchron (CNS) began at 119.70 ± 0.12 Ma and that the average seafloor spreading rate during the CNS was ~3.5% higher than that inferred from GTS 2020. It also suggests that oceanic anoxic event 1a began at 119.40 ± 0.12 Ma, thereby providing an updated chronologic basis for exploring the primary trigger of this carbon cycle perturbation.

Original languageAmerican English
JournalGeosciences Faculty Publications and Presentations
StatePublished - 1 Jun 2023

Keywords

  • Ar-40/Ar-39
  • Asia
  • Bayesian analysis
  • argon
  • carbon
  • carbon cycle

EGS Disciplines

  • Earth Sciences
  • Geophysics and Seismology

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