Extraterrestrial impacts and their consequences for the biosphere

The K-Pg mass extinction was an important period of Earth’s history, reducing biodiversity by some 75% and paving the way for mammals to rise to ecological dominance. Occurring 66 million years ago, a large asteroid collided with the Earth’s surface as the Deccan Trap large igneous province was also active. Although the K-Pg asteroid impact is the likely primary driver behind this mass extinction, it is difficult to measure the impact of the co-occurring volcanism on the extinction event.

A high-resolution Paleogene surface temperature record is utilised to investigate the biosphere’s recovery on Earth following the K-Pg impact.

This thesis showcases the development and usage of a new model that allows for the injection of discrete, single-time events into a non-linear interpolating solver; this injection is used to emulate recovery after the K-Pg impact in deep-time. This model, called SMITE, utilises a dynamic vegetation model linked to a climate and biogeochemical model. SMITE is used to explore the hypothesis that vegetation change due to the impact could have driven the temperature profile of the geological record; the confirmation of which would negate the impact of the large igneous province.

I find that plausible vegetation feedbacks can reproduce the duration of warming seen within the geological record, but the model overpredicts the degree of warming present after the K-Pg impact, indicating that relatively low fire intensities or very fast regrowth times may be more plausible than severe scenarios. This work supports the hypothesis that vegetation recovery following the impact was rapid, and that the asteroid impact was the likely primary driver behind the K-Pg mass extinction.

Future work aims to better constrain vegetation re-establishment and regrowth to better recreate the geological record.