The Bathonian–callovian Boundary: New Insights from Argentina and France

Significant challenges remain in formally defining geological stage boundaries, particularly where globally diagnostic biostratigraphic markers and robust geochronological or geochemical constraints are lacking. The Bathonian–Callovian boundary exemplifies these difficulties, with no formal agreement on its placement to date. Multiple datasets have been developed and published for this interval, including magnetostratigraphy from Europe, U–Pb geochronology from the Neuquén Basin, Argentina, Re–Os ages from Svalbard, and integrated carbon-isotope and biostratigraphic from Greenland and France. However, correlation remains problematic, largely due to the cosmopolitan nature of ammonite faunas and resulting inconsistencies in biostratigraphic frameworks. Here, we present new multi-proxy records of two sedimentary successions from the Loma Baya section (Neuquén Basin, Argentina) and Ravin des Vas section (Subalpine Basin, France), both encompassing the Bathonian–Callovian boundary. High-precision radiometric ages from Argentin aalong with a Bayesian Age-depth model, integrated with carbon-isotope stratigraphy, ammonite and nannofossil biostratigraphy from both sections allow correlation and a revision of the age of the base of the Callovian. These data have hence further implications for the Oxfordian and broader Late Jurassic timescale. The age of the section is also constrained by strontium-isotope analysis of three belemnites, indicating the Bathonian–Callovian boundary interval by comparison with the European reference curve. The integrated, multi-proxy data sets from this continuous succession suggest a new age for the Bathonian–Callovian boundary and the possible application of a network of well-defined and well-constrained auxiliary Global Stratotype Sections and Points (GSSPs) to support the boundary characterization.