Mass extinctions in earth history

The Cretaceous-Paleogene Boundary Extinction

Everyone knows that the around the time the dinosaurs went extinct, a huge asteroid collided with Earth, and this forms the most popular hypothesis for their extinction (along with lots of other flora and fauna). An alternate, or complementary, hypothesis is that the eruption of millions of cubic kilometers of basalt and the associated volcanic gases from the Deccan Traps led to climate change, acid rain and ocean acidification that could have devastating effects of ecosystems. This is the mechanism by which most other mass extinctions are thought to have occurred. Though the stratigraphic evidence for the role of bolide impact is well-documented, testing the importance of the Deccan Traps in the end-Cretaceous disaster is more difficult and requires high-precision geochronology. This work for the moment focuses on determining the timing, duration, and tempo of eruption of the Deccan Traps to relate them to the timing of extinction and impact and also to place quantitative estimates on the flux of volcanic gases into the atmosphere to help constrain potential climate effects.

The Triassic-Jurassic Boundary Extinction

Around 201.4 million year ago, one of the largest mass extinction events in Earth history is recorded in the stratigraphic record. Associated with this event are major shifts in the carbon cycle, sea-level, and CO2 levels in the atmosphere. Directly or indirectly related to the TJB is the eruption of the central Atlantic magmatic province (CAMP), one of the largest flood basalt eruptions ever. The temporal and genetic relationship between all of these processes remains enigmatic, though our work combining biostratigraphy, sedimentology, the stable isotope record, and geochronology is helping tease out the timescales and global significance of these catastrophes. The goals of this ongoing work are to determine, 1) the duration and synchrony of global mass extinction, 2) the rates and processes of post-extinction biological recovery, and 3) the significance and causes of carbon cycle perturbations.