In December 2013 a research team from the Department of Geosciences traveled to central India in order to address one of the most captivating questions in Earth history: what was the cause of the dinosaur-eradicating Cretaceous-Tertiary (K-T) mass extinction ca. 65 million years ago? The group included Profs. Blair Schoene and Gerta Keller; Kyle Samperton, a PhD student working in Schoene’s Thermal Ionization Mass Spectrometer Laboratory; Mike Eddy ’11, now a PhD student in the Department of Earth, Atmospheric and Planetary Sciences at MIT; Prof. Thierry Adatte of the University of Lausanne (Switzerland); Prof. Syed Khadri of Sant Gadge Baba Amravati University (India); and Preston Kemeny ’15, who is conducting his Spring Junior Project under the supervision of Keller, Schoene, and Adatte.
The group’s goal was to investigate the Deccan Traps, a massive continental flood basalt province with an estimated eruptive volume of one million (106) cubic kilometers, or a million times larger than the 1980 Mount St. Helens eruption! Today the Deccan lava flows blanket much of the Indian subcontinent, including where the team worked in the state of Maharashtra, home to large cities like Mumbai and Pune. Scientists have previously speculated that the eruption of the Deccan Traps may have been contemporaneous with the K-T extinction, suggesting a causal link between the events. Significantly, the K-T extinction is the most recent of the five major mass extinctions on Earth, and is thus of extreme interest to the geoscience community for understanding the mechanisms and durations of these catastrophes. While some researchers think that an asteroid impact near Chicxulub, Mexico, was the sole cause of the extinction, other evidence points to a one-two punch by the asteroid plus volcanic emissions from Deccan that dealt a fatal blow to the global carbon cycle and caused planet-wide ecosystem collapse. “However,” says Samperton, “In order to nail down a definitive cause-and-effect connection between Deccan, Chicxulub and the K-T extinction, better absolute time constraints for Deccan than currently exist are needed.” For example, existing geochronological data have temporal uncertainties of several hundred thousand to millions of years. “While insightful, these data are simply not precise enough to confirm or disprove Deccan causality for the K-T extinction.”
Prof. Blair Schoene and Mike Eddy ’11 investigating a quarry of Deccan Traps basalt near Pune, India. Photo by Kyle Samperton
In order to more finely resolve the timing and duration of Deccan volcanism, the Princeton team collected samples during two weeks of field work with the goal of finding dateable minerals like zircon, which commonly crystallize in volcanic rocks. If found, Schoene’s group at Princeton can date the Deccan basalt flows and generate data with an order of magnitude better precision with the lab’s Thermal Ionization Mass Spectrometer (TIMS), which measures trace amounts of uranium and lead in a mineral’s crystal lattice.
“We’re excited to see how this project unfolds,” says Schoene, “It’s fun to work on something like the dinosaur extinction that’s of interest to my 5 year old son as well as professional geoscientists!”
Note: this research was supported by the Department of Geosciences’ Scott Fund.
Princeton team examining the Karla Buddhist temple built into Deccan lava flows around 200 BC. MIT GS Mike Eddy ’11, Prof. Gerta Keller, Prof. Blair Schoene, GS Kyle Samperton, and Preston Kemeny ’15. Photo credit by Prof. Gerta Keller