Another one bites the dust: Photosynthetic collapse after the Chicxulub impact

Abstract The Chicxulub impact triggered a global impact winter at the Cretaceous-Paleogene (K-Pg) boundary 66 million years ago. Yet, the exact killing mechanisms of the K-Pg mass extinction including the wipe-out of non-avian dinosaurs, remain poorly constrained. Here, we present paleoclimate simulations based on new sedimentological constraints from an expanded K-Pg boundary deposit in North Dakota, to evaluate the relative and combined effects of impact-generated sulfur and silicate dust as well as soot from global wildfires on the post-impact photosynthetic activity. In prior works, the relative contribution of dust was considered peripheral compared to the other types of fine-grained ejecta. However, our results show that a massive plume of micrometer-sized silicate dust was a key factor driving the K-Pg impact winter due to a long atmospheric lifetime at least 20 years. The dust-induced photosynthetic shut-down, together with additional effects of soot and sulfur, led to the catastrophic collapse of primary productivity on land and in the ocean, steering the mass extinction in the direct aftermath of the Chicxulub impact.