Refined chronologies of magnetochron M0r reveal asynchronous terrestrial and marine carbon isotope responses to Oceanic Anoxic Event 1a.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 41779858.
- Also identified by DOI 10.1126/sciadv.aea8374 and PMC identifier 12959394.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
The base of magnetochron M0r has been informally used to calibrate the onset of Oceanic Anoxic Event 1a (OAE1a) and place the Barremian-Aptian boundary; however, its precise age remains a subject of debate. Here, we present a 1497.5-m continuous drill core from the Lower Cretaceous lacustrine Jiufotang Formation in North China. High-resolution cycle-calibrated magnetostratigraphic analyses precisely constrain the termination of Chron M0r to 121.26 ± 0.38 Ma. The carbon isotope excursion associated with OAE1a in the same core postdates the termination of Chron M0r by 1.24 ± 0.4 Myr, substantially longer than ~0.3 to 0.66 Myr offset observed in marine records. This refined chronology provides direct evidence for asynchronous carbon cycles between terrestrial and marine systems during OAE1a, thereby challenging the prevailing hypothesis of rapid atmospheric CO<sub>2</sub> emissions at the onset of OAE1a.