Author ORCID Identifier

Date of Award

Winter 2024

Document Type

Thesis (Master's)

Department or Program

Earth Sciences

First Advisor

C. Brenhin Keller


The end-Cretaceous mass extinction was marked by both the Chicxulub impact and the ongoing emplacement of the Deccan Traps flood basalt province. Both of these events perturbed the environment by the emission of climate-active volatiles, primarily CO2 and SO2. To understand the mechanism of extinction, we must disentangle the timing, duration, and intensity of volcanic and meteoritic environmental forcings. In this thesis, we used a parallel Markov chain Monte Carlo approach to invert for the aforementioned volatile emissions, export productivity, and remineralization from 67 to 65 million years ago using the LOSCAR (Long-term Ocean-atmosphere-Sediment CArbon cycle Reservoir) model. The parallel inversion leverages 128 cores in a replica exchange algorithm, where each core can exchange current solutions between each other proportional to how well their model outputs match the sedimentary record. Our results closely match observed and proxy data and suggest that CO2 and SO2 emissions were decoupled, there was a two-step decline in export productivity with a protracted recovery, and there was no clear volatile impulse at the boundary. This implies that, to the extent that the Chicxulub impact made life untenable for non-avian dinosaurs, it was not directly due to its CO2 and SO2 emissions. More broadly, our methods provide a potential path forward for efficient parallel inversion of complex Earth system models, since we show that the method is perfectly scalable up to at least 512 cores. Any model for which the run-time is longer than the communication time between cores can be sped up using our method.

Original Citation

Alexander A. Cox, C. Brenhin Keller, A Bayesian inversion for emissions and export productivity across the end-Cretaceous boundary. Science 381, 1446-1451 (2023). DOI:10.1126/science.adh3875