New Impact Model for the Late Triassic Manicouagan Crater

The Manicouagan impact event, precisely dated to 215.40 ± 0.16 Ma, created one of the largest impact craters of the Phanerozoic. The crater is located in the Grenville Province of the Canadian Shield and has a rim-to-rim diameter of 85–100 km. Despite the event’s potential significance, its environmental and climatic consequences remain debated. We performed iSALE (impact-Simplified Arbitrary Lagrangian-Eulerian) hydrocode simulations against the target lithologies, which yielded three best-fit models of projectile 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 that reproduced crater diameters of 90, 95, and 100 km, respectively. The iSALE models enhance our understanding of the Manicouagan cratering processes and quantify its environmental effects through defining a constrained range of projectile sizes and velocities, thereby providing the basis for estimating the scale of the associated environmental effects. The energy released was estimated to be 1.17–1.27×1023 J (2.8–3×107 Mt TNT). Scaling relationships were used to estimate melt, vapor, condensate, and fine dust production. Our results were compared to the Earth Impact Effects Program, which is a web-based program for estimating the environmental aftermath of a meteorite impact. Although the modeled energy release exceeds nominal thresholds for global catastrophe, estimated atmospheric sub-micrometer dust loading (<10¹³ g) is below the blackout threshold of 1016 g required to induce prolonged photosynthetic shutdown. Airblast, ejecta deposition, and thermal effects are largely regional in extent and unlikely to have triggered sustained or significant environmental and climatic perturbations.