Astronomical pacing of the Ludfordian Biogeochemical Event, the largest carbon cycle perturbation of the Phanerozoic

The Kosov Quarry section (Prague Basin, Czech Republic) preserves one of the most complete Silurian successions spanning the Ludfordian (late Silurian) Biogeochemical Event (LBE), encompassing the mid-Ludfordian Carbon Isotope Excursion (MLCIE), the largest positive δ13Ccarb excursion of the Phanerozoic. The LBE is associated with climatic cooling, redox reorganisation, sea-level change, and faunal turnover, yet its tempo and driving mechanisms have remained poorly constrained. Here, we establish an anchored astrochronology for the Kosov Quarry succession based on lithological induration patterns and anchored to the Ludfordian–Pridoli boundary. The resulting age model resolves astronomical cycles from half-precession (~8.5 kyr) to 405-kyr eccentricity cycle and constrains the onset of the LBE to 424.30 ± 0.60 Ma, with a total duration of 1.15 ± 0.26 Myr. The Lau–Kozłowskii Bioevent, representing a brief extinction pulse during the culmination of the Siluricus ocean anoxic event just before the MLCIE, lasted 30 ± 10 kyr. Spectral and phase analyses reveal a strong imprint of the eccentricity cycles in the induration, lag-1 sea-level, and δ13Ccarb rate-of-change (‰/kyr) records. Phase relationships indicate that the sea level was subjected to a glacio-eustatic regime. The δ13Ccarb change rate reached up to 0.09 (‰/kyr), implying rapid carbon burial during eccentricity minima, transient CO₂ drawdown, and possible glacial expansion. These results demonstrate that eccentricity pacing exerted a first-order control on Silurian carbon-cycle feedbacks and sea-level change. Our astrochronology provides the first high-resolution temporal calibration of the entire LBE and a quantitative framework for integrating astronomical forcing into Palaeozoic carbon-cycle perturbations.