Revised onset age of magnetochron M0r: Chronostratigraphic and geologic implications

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