By Brian Cameron
A cataclysmic flash occurred 65 million years ago on an area of the planet that we know as Mexico’s Yucatan Peninsula. It was a blast so large it sent earthy debris hurling into space to eventually land on Mars, amongst other celestial bodies. This epic collision represented one of the most iconic turning points in Earth’s biological calendar.
The asteroid’s impact sent a massive tsunami, up to a thousand feet high by some estimates, over oceans and plains, depositing trillions of tons of particulates into the atmosphere resulting in a devastating nuclear winter, enacting the demise of those terrible lizards that decorate our museums today.
Known as the Chicxulub impact, there has been no single event to dramatically impact the ways of life on Earth since, and until last week there had been no direct evidence as to the immediate fallout of that impact. Coincidentally, that evidence was found just west of downtown Bowman.
The Hell Creek Formation
Recently, the community of Bowman was made visible to some of the world’s largest publishers–from CNN, BBC, The Atlantic, The New Yorker–the list goes on. And it all circulated around a truly groundbreaking discovery in the world of paleontology by Robert DePalma, a doctoral student in geology who works in the Kansas University Biodiversity Institute and Natural History Museum.
In 2012, DePalma started excavation in and around the Hell Creek Formation, a geological area that spans from Montana to parts of Wyoming, South and North Dakota. In this case it was just outside of Bowman, though this wasn’t DePalma’s first visit to the area.
“I have been doing field work in the Dakotas since I was in high school, every single summer, so I essentially grew up out there,” Robert DePalma said. “I feel a sense of connection to it, and I have developed just as many nostalgic ties to the people and places out there as I have in my hometown in Florida.”
DePalma first started coming to the Bowman area when he was in high school, and since then he has made the area, specifically the Hell Creek formation, the central figure of his professional career.
What DePalma found was at first highly suspect, as are most extraordinary discoveries in science, but as time went on and more notable minds became aware of his work it quickly dawned on him that he may be responsible for one of the most impactful paleontological discoveries made this century.
“A tangled mass of freshwater fish, terrestrial vertebrates, trees, branches, logs, marine ammonites and other marine creatures were all packed into this layer by the inland-directed surge,” DePalma said.
Everything DePalma was finding was located right at the KT boundary, the geological stratum that depicts the physical separation of the Cretaceous and Tertiary periods.
This alone suggests that these fossils were compiled right at the time of the extinction–level event, and if previous research had anything to say, then these organisms were direct casualties of the Chicxulub asteroid impact.
The proverbial smoking gun for DePalma’s discovery wasn’t just the fact that he stumbled on some of the most exquisite fossils ever found, from various species, nor the fact that they were so close to the extinction boundary, but instead, it was the abundant presence of tiny little things called Microkyrstites.
When the asteroid smacked the surface of the planet it sent a massive amount of debris skyward. Superheated to temperatures that rival our sun’s surface, much of the particulates were in the form of a huge vapor plume, that once combined with the extreme heat of the impact condensed together to make tiny spheres of glass.
These near-microscopic particles then rained back down upon the Earth’s surface.
Interestingly, these microkystite spherules rained over what is now North Dakota (among other places) in the first hour after the impact. In turn, those tiny glass spheres were encountered by creatures living at the time, notably fish that resided in and around the Western Interior Seaway.
“The fish were buried quickly, but not so quickly they didn’t have time to breathe the ejecta that was raining down to the river,” said co-author David Burnham, preparator of vertebrate paleontology at the KU Biodiversity Institute. “These fish weren’t bottom feeders. They breathed these in while swimming in the water column. We’re finding little pieces of ejecta in the gill rakers of these fish, the bony supports for the gills. We don’t know if some were killed by breathing this ejecta, too.”
One thing remained a mystery for DePalma, however. They calculate that the massive tsunami took approximately seventeen hours to reach North Dakota. If that were the case the ejecta spherules would already be deposited on the ground. So, why were they finding lots of evidence of animals that weren’t along the bottom that had the tiny particles in their gills?
“A tsunami would have taken at least 17 or more hours to reach the site from the crater, but seismic waves — and a subsequent surge — would have reached it in tens of minutes,” DePalma said.
DePalma described a known scientific phenomenon called a ‘seiche,’
“As the 2011 Tohoku earthquake in Japan showed us, seismic shaking can cause surges far from the epicenter,” he said. “In the Tohoku example, surges were triggered nearly 5,000 miles away in Norway just 30 minutes after impact. So, the asteroid impact could have caused similar surges in bodies of water worldwide, giving the first rapid ‘bloody nose’ to those areas before any other form of aftermath could have reached them.”
It was this ‘bloody nose’ that DePalma found, evidence of a local tsunami that happened nearly simultaneously to the falling debris, before the larger wave arrived. Giving light, for the first time, to direct casualties, in fossil form, of the largest event to happen in the history of animal life on Earth, an event that would lead to the extinction of 75 percent of all life on the planet at the time.
Back to Bowman
For now, DePalma has his work cut out for him. This past week, his findings were published in the Proceedings of the National Academy of Sciences as well as a worldwide media blitz that led to his name on the tip of paleontology’s tongue. But if there’s one thing he recalls of his times in and around Bowman, it’s the genuine curiosity of the community, and why he’s drawn to SW North Dakota.
“Whenever there is an opportunity for my research team to give back to the greater scientific community as a whole, it always delights us to see the happy faces much closer to the study region, as they learn about the fascinating facts locked in the land right outside their homes,” DePalma said. “And, this also is a wonderful spark for the younger crowds, inspiring them to learn more and be stewards of the resources around them. So to me-and the rest of the team, actually–the satisfaction of this work is not just in making the intriguing discoveries, but also getting to tie them into the local groups.”
DePalma will be back once the snow melts and the rains die down. He and his research team will be back in Bowman, sifting through history and piecing together one of the biggest finds in the last few decades.
“It is a fascinating and fun process, and I look forward to expedition time all year long,” DePalma said. “The summer is when I am truly alive, out there in the American West.”