A New Impact Model for The Norian, Late Triassic Manicouagan Crater

Abstract Meteorite impacts can lead to significant disruptions of Earth’s systems, potentially affecting the planet's climate, ecosystems, and environment. The Manicouagan impact event is recorded by one of the largest impact craters of the Phanerozoic era, located in Quebec, Canada in the Grenville Province of the Canadian Shield, with a rim-to-rim diameter of 85–100 km. It has a precise age of 215.40 ± 0.16 Ma, yet its environmental aftermath remains poorly constrained, particularly any robust link to the Norian, Late Triassic extinction pulses or carbon-cycle perturbations. Here we present a new impact-Simplified Arbitrary Lagrangian-Eulerian (iSALE) hydrocode simulation against the Manicouagan’s target lithologies to constrain the most plausible impactor diameters and velocities that would reproduce the observed crater morphology. Three best-fit models of crater diameters and velocities of 7.2 km at 20 km s-1, 8.8 km at 15 km s-1, and 10.4 km at 12 km s-1 reproduced crater diameters of 90, 95, and 100 km, respectively. We calculated the kinetic energy delivered by each projectile, which is on the order of 1.17–1.27x1023 J. The calculated energy is sufficient to vaporize the entire projectile and a considerable amount of the upper target lithologies, and melt large volumes of the target rocks. We then estimated the mass of vapor released into the atmosphere by using scaling relations and assessed the potential post-initial settling of the vapor mass after condensation and re-entry to be ~5x1017 g. This exceeds the ~1016 g blackout threshold required to cause global cessation of photosynthesis, darkness, and cooling. Our results provide numerical assessments of the environmental consequences of the Manicouagan impact event and a framework for reassessing its potential role in Late Triassic biotic and climatic events.KeywordsManicouagan Impact Event, Hydrocode modeling, iSALE simulations, Late Triassic, Environmental consequences.