233-7 Using an Earth System Model to Evaluate Kill Mechanisms Associated with the End-Cretaceous Mass Extinction

Session: Impact Cratering and the Evolution of Life

Presenting Author:

Clay Tabor

Authors:

Tabor, Clay Richard¹, Hu, Shixiong², Bardeen, Charles³, Coupe, Josh⁴, Harrison, Cheryl⁵, Lovenduski, Nikki⁶, Tessler, Maya⁷, Toon, Brian⁸

Abstract:

The Cretaceous–Paleogene boundary is defined by a layer of iridium deposited from an asteroid impact 66 million years ago. This asteroid impact is the primary culprit for the end-Cretaceous mass extinction. However, the specific kill mechanisms responsible for this mass extinction remain speculative. Hypotheses include an infrared pulse, acidification, light reduction, cold temperatures, and ultraviolet radiation. Here, we use an Earth system model, which notably includes a high-top atmosphere, more complete atmospheric chemistry, an explicit aerosol-resolving scheme, and ocean biogeochemistry, to simulate the asteroid impact event at the Cretaceous–Paleogene boundary. Our simulations agree with geologic evidence for widespread fires soon after the impact, providing support for a strong infrared pulse, which may have been the primary driver of the terrestrial extinction. In the ocean, we find that a reduction in sunlight, and the associated cessation of photosynthesis, was the main killer of primary producers. The prolonged loss of primary producers, in turn, could have led to the recorded extinction of higher trophic levels. Although acidification likely negatively affected marine life as well, our findings suggest it may have only played a minor role in the marine extinction. The low-light conditions also led to extreme surface cooling, especially on land, which likely exacerbated the extinction. Finally, after sunlight returns to the surface but before stratospheric ozone recovers, our simulations show a pulse of ultraviolet radiation, which potentially delayed recovery.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-9503

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