In September 2017 DIG Director Dr. Greg Wilson and Wilson Lab graduate student Luke Weaver embarked on a trip to India to investigate the Cretaceous-Paleogene (K-Pg) mass extinction event, which is famous for marking the end of the “Age of Dinosaurs” and the beginning of the “Age of Mammals.” See below for an exciting account of the trip by Luke!
India Trip 2017
The primary research focus of the Wilson Lab is to understand how vertebrate, especially mammal, communities were affected by the K-Pg mass extinction event, which wiped out non-avian dinosaurs and set the stage for placental mammal radiation. The cause of this extinction event is often attributed solely to a bolide impact which occurred right at the K-Pg boundary, the evidence of which is seen globally as an iridium-rich impact horizon, and locally as a massive crater near the Yucatan peninsula. However, at least 1 million years before this impact event, volcanoes in western India, called the Deccan Traps, began erupting, emitting massive amounts of greenhouse gases into the atmosphere. Research by the Wilson Lab and by DIG Instructor Dr. Tom Tobin, conducted in northeastern Montana, has suggested that this volcanic activity in India may have destabilized Late Cretaceous ecosystems prior to the K-Pg boundary and left them vulnerable to a large environmental perturbation, such as a bolide impact.
In order to further test this hypothesis, Dr. Greg Wilson and colleagues have been exploring the fossil-rich, “Intertrappean beds” of western and central India, which were deposited between Deccan Traps eruptions. These beds span the K-Pg boundary and preserve an assortment of vertebrate microfossils, such as frogs, fish, dinosaurs, and mammals which lived at “ground-zero” for Deccan Traps eruptions. Through collaborations with other paleontologists, geologists, and geochemists, research on the intertrappean beds of India will allow us to compare and contrast environmental and biological change across the K-Pg boundary in India to that of eastern Montana, with the goal of getting a more global picture of the drivers and consequences of the K-Pg mass extinction.
Greg and I traveled to India in mid-September on a reconnaissance mission. Our goal was to visit the fossil collections at the Geological Survey of India (GSI) – Southern Region, and to conduct fieldwork near the villages of Naskal and Rangapur in central India. Our work at the GSI was a huge success, as we were able to study a diverse array of mammal fossils, including bizarre rodent-like mammals called gondwanatherians, which are now extinct. From there it was on to fieldwork. In total, we visited three sites and collected over 1,000 lbs of sediment, which we will ship back to the U.S. to sieve in screen boxes with water and to pick out the tiny fossils under a microscope. Although this process is long and arduous, it allows us to find very small and rare fossils that we could never detect by simply looking at the surface of a rock outcrop. Although these microfossil assemblages mostly consist of isolated teeth and vertebrae, they allow us to get a more complete picture of the vertebrate ecosystem, compared to what we can learn from just a single, nicely preserved individual skeleton.
In addition to sediment collection, Greg and I worked with geologist Dr. Dhananjay Mohabey and fossil pollen expert Dr. Bandana Samant, both from Nagpur University, to begin to reconstruct the environments in which these microfossils accumulated. Dhananjay also took a variety of paleomagnetism samples, which will allow us to better constrain our fossil localities in time. In total, it was a whirlwind trip that only lasted about 10 days, but the work we completed has now set the stage for Greg to return in January and pick up where we left off.
Funny story: While we were working the Naskal site, we heard some commotion from down the path. The noise continued to grow until suddenly, from around the bend, emerged a whole herd of cattle being driven straight through our fossil locality! The cattle driver, apparently ambivalent to our presence, pushed the cattle forward as we scurried out of the way. Some of the locals who were helping us began yelling at the man and telling him to not let the cows trample over our site, where we had all of our gear and bags of sediment sitting. At the last minute, the man jumped into action and forced the cattle up the hillside, avoiding our fossil site, leaving the rest of us to gawk at the stream of cattle that continued to emerge from around the bend.