A research article published in April 2019 has created seismic waves in the study of paleontology.
At a dig in southwestern North Dakota known as the Tanis site, paleontologists found evidence of an inland surge of water that encased animals and plants in mud minutes to hours after an impact. Researchers have attributed this snapshot of mass death to the Chicxulub asteroid that ended the Cretaceous period in a heartbeat. The Tanis site is found in the Hell Creek Formation, one of the richest deposits of fossils in the world. It's in this same formation, southeast of Tanis, that the T. Rex named Sue was found.
It's also where the Keystone XL pipeline is partially routed. After years of permit battles, TransCanada has now broken ground at the U.S.-Canada border and at worker camps in South Dakota and Montana. Construction in Nebraska will come later.
Victoria Wicks has listened to years of testimony before licensing boards, legislative committees, and state and federal courts. She has frequently heard witnesses argue for protection of human history and assets: the burial grounds, cultural and religious sites, mineral estates, and water resources. But preservation of fossils was rarely addressed.
She wondered why, and what might be uncovered in a pipeline trench through Western South Dakota. The result of her research is the subject of this segment of SDPB's In the Moment.
Victoria Wicks: Robert DePalma describes the meteoric cataclysm on the day the dinosaurs died.
Robert DePalma: We know there would have been a tremendous air blast from the impact and probably a loud roaring noise accompanied with that similar to standing next to a 747 jet on the runway.
Victoria Wicks: DePalma's name is listed first on the research article published in April last year, and he has been the primary spokesman on the story covered internationally since then. He says an asteroid about the size of Mount Everest came in at 20 kilometers a second, that's more than 44,000 miles an hour, and hit the earth near the Yucatan Peninsula at the Southern tip of what is now called North America. The impact obliterated the asteroid itself and blasted a crater in the earth. The resulting cascade brought on the third largest mass extinction the planet has known.
Robert DePalma: Within a matter of minutes to hours, you would have seen the first effects there in the Dakotas. So you would have felt seismic shaking within the first tens of minutes. You would have had little glass beads that were red hot raining down through the sky that were blasted out of the crater. They would have started coming down minutes after impact.
Victoria Wicks: DePalma says the event would have been close to hell on earth for the first day. And then it would have settled into continuous, awful conditions that destroyed most of life on earth. That impact abruptly ended the Cretaceous Period, leaving an actual visible timeline in Earth's layers.
Robert DePalma: You can literally put your finger on it and say, well, my finger's right now resting between the Cretaceous and Paleogene. You can see it and you can study the ecologies above and below that boundary. So we know that the impact is well-preserved there.
Victoria Wicks: The seismic shaking DePalma describes caused a seiche or sympathetic tsunami that traveled up the river system he's studying at the Tanis site. That surge preserved a three-dimensional historic record of fauna and flora at the moment of death. One of the most widely published photos from the dig is a cluster of paddlefish and sturgeon with glass beads or tektites embedded in their gills, posed in sediment as if they are swimming with the currents.
Robert DePalma: You can look at all of the carcasses of the animals that were tossed into that deposit and entombed and the impact event, suddenly it does not seem quite as abstract. We already know what the global consequences were, but this is the first site ever found that has articulated carcasses of animals that we know died on that day of impact.
Victoria Wicks: Fossil excavation often turns up impressions of things that have left an imprint, but the fossil record from the day of destruction captures not just things, but the action that killed them. In grammatical terms, this discovery puts verbs to the knowns and turns symbol into metaphor.
Robert DePalma: So we can excavate those deposits and visibly look at, essentially, the first victims in the Dakotas of that impact. So we can see these animals in three dimensional preservation, not flattened out as they are in many other fossil sites. And we can understand aspects of their anatomy that we really couldn't at other sites because the preservation just wasn't sufficient.
Victoria Wicks: DePalma says when you walk through the Hell Creek Formation, you can see bones exposed on the surface. They're probably eroded and not of much value, but bones on the surface can indicate bones underneath the ground where they're in a stable environment preserved until they're dug up.
Robert DePalma: The Hell Creek Formation was absolutely packed with dinosaurs. It is known for very plentiful dinosaur fossils.
Sally Shelton: This is one of the most fossil wealthy areas in the world, is Western South Dakota.
Victoria Wicks: Sally Shelton is a paleontologist who taught and managed the fossil collection at the South Dakota School of Mines for 11 years. She left there at the end of 2019, but at the time of this interview, she was standing on a geographical map on the floor of the school's paleontology research lab.
Sally Shelton: The Hell Creek is some of the most important dinosaur deposits in the world. And this also crops out in Montana and other places around here. So Hell Creek is where we get the really famous dinosaurs, the T-Rex kind of things. There are a lot of other smaller things that go with that.
Victoria Wicks: Shelton notes that the Eastern side of South Dakota was scraped flat by glaciers, making the land great for farming, but not so great for major fossils. She points out, however, there are exceptions.
Sally Shelton: The Mosasaur, or Big Mo, that we have on exhibit in the museum came from Brown County. They were building a dam in the 1940s and a 12-year-old boy playing in the debris found some bones. They traced them back and we've got this magnificent Mosasaur that came from there.
Victoria Wicks: And that's the sea, from the sea.
Sally Shelton: Yeah. So you never know. You really never know, but from a predictability point of view, we're sure you're going to run into fossils on this line that you're talking about.
Victoria Wicks: We turn our attention to the map below our feet, now looking at an area adjacent to the southern edge of Hell Creek. We're talking about just south of Cheyenne River, Jones.
Sally Shelton: Yeah, this is all pure shale, this green that you're looking at. And this is all the ocean floor deposits from that Western Interior Seaway.
Victoria Wicks: The Seaway we're discussing is the salt water body that once covered the center of North America. The land where South Dakota, North Dakota and Nebraska now lie was at one time completely underwater, home to an assortment of sea creatures. The Chicxulub asteroid landed just to the South of that sea and caused the tsunami that then surged into the river system at the Tanis site. Shelton says the pure shale formation contains fossil rich ocean deposits. She notes that not all fossils are created to be equal. Some are exciting finds in rare condition or offering new information, others are not.
Sally Shelton: And that's where you need an expert. You need somebody who does the monitoring and mitigation work to look at them and say that this is not a significant new deposit or stop the trucks, it is.
Victoria Wicks: Over the past decade, the Keystone XL Pipeline has been the subject of a number of environmental and economic studies. Two of them published in 2012 and 2014 by the US Department of State are still in play as evidence by TC Energy's quarterly reports to the South Dakota Public Utilities Commission. Included in these studies are data on fossil resources that might be affected by pipeline construction. Paleontological surveys identified a long list of locations along the pipeline route that should be monitored. Peter Larson is a paleontologist who walked some of the pipeline's path in advance of the 2012 study. He was asked by ranchers to protect their interests, where the pipeline was routed to cross their land.
Peter Larson: We actually walked kitty-corner across Harding County, along with the archeologists who were serving for archeological sites along the pipeline. We found fossils, we found artifacts as well. So we know they're going to be disturbing and maybe even going through entire skeletons and that sort of thing.
Victoria Wicks: To accommodate a 36-inch pipe with sufficient cover, the trench has to be at least five feet wide and six feet deep and deeper in certain terrain with a wide corridor scraped clean on either side. Larson predicts inevitable damage.
Peter Larson: When they're going through not just outcrops of the Hell Creek, but also through grassy plains, they're going to be disturbing this fossiliferous horizon. And it's very unlikely that they'll be able to actually see anything during the excavation of the hole, so they're going to be destroying, of course, destroying some fossils. Hopefully they will have a paleontologist or at least one paleontologist on site that can stop them if they hit something that's of significance.
Victoria Wicks: Larson notes that he helped survey the land at no charge to show thanks to the Harding County ranchers who have allowed him to dig on their land. And he says the benefits have been reciprocal.
Peter Larson: One good thing about us doing this, going up to help the ranchers, is they were able to make a much better deal with the pipeline first.
Victoria Wicks: He also says ranchers could stand to make a considerable amount of money if a significant fossil is found on their land and the agriculture economy being what it is, the extra income wouldn't hurt. Larson is one of the scientists who uncovered the T-Rex named Sue and he also contributed to the Tanis research. Both discoveries were made in the Hell Creek Formation.
Peter Larson: So it's a really important series of rocks that shows, among other things, how diverse the fauna was during moments leading up to the actual asteroid impact. And it's very important because there are very few places on earth where this event is chronicled in terrestrial rocks.
Victoria Wicks: Larson's curiosity and excitement is kept alive by his involvement in a field of study that constantly surprises. Dinosaurs are cool and the more we know about them, the cooler we find them to be.
Peter Larson: There's about 122-million-year-old deposits near Liaoning, China. And there, they discovered, over the past 30 years, have discovered a whole host of feathered dinosaurs. Dinosaurs with actually feathers preserved, which led us to the hypothesis that probably all dinosaurs had some sort of body covering, whether it be feathers or what you might call proto feathers, or hairlike projections.
Victoria Wicks: Larson says digs in the Hell Creek Formation as well as sites in Wyoming have unearthed skin that indicates T-Rexes had feathers, making generations of artist illustrations inaccurate.
Peter Larson: If anybody's ever looked at chicken skin, you can see those pores where the feathers have been removed.
Victoria Wicks: All the depictions of dinosaurs, it might be like showing pictures of a plucked chicken?
Peter Larson: Yeah, yep. In many instances, it might be that.
Victoria Wicks: Larson says baby dinosaurs probably hatch from their eggs already covered with down that protected them from heat and cold. And he says dinosaurs like their descendants, the birds were in all probability warm blooded. The term dinosaur applies only to land animals except perhaps for the Spinosaur. Larson says the reptiles who lived in the Western Interior Seaway and swam in the ocean are called something else, but they all suffered the same fate.
Peter Larson: There were Mosasaurs, which are relatives of the Komodo dragon and other monitor lizards. There were giant sea turtles that are related to the sea turtles of today. And there were also things called plesiosaurs, both long necked and short neck plesiosaurs, which are, I guess you'd think of the Lochness Monster if you want to get an image of what one of the long neck plesiosaurs looked like. And these guys were still here, still around, and they also went extinct with the dinosaurs because of this asteroid that struck the earth.
Victoria Wicks: Larson says when these land and sea creatures died off, mammals found a niche where they could evolve and diversity was restored, but that evolution took millions of years. And it is from that fact that we discover the lessons to be learned by studying fossils.
Peter Larson: One of them is, of course, what humans are doing to this planet. We'll never see a duck-billed dinosaur on this planet again and they were magnificent animals. And if we think about what's happening in Africa and we're losing our megafauna in Africa and Asia, rhinos and elephants and tigers and lions and bears, oh my.
Victoria Wicks: Larson says human activity is decreasing the diversity of the animals and plants that live on earth. And when that happens, the habitats and other species that rely on them also disappear. These extinctions are not as immediate as when the Chicxulub asteroid hit, but unstopped, they are just as certain.
Peter Larson: As you wipe out the diversity, you can actually precipitate a tremendous crash of the system like what happened 66 million years ago when this asteroid crashed into the earth. And it took millions of years to recover, for the planet to recover and recover that diversity. We have a responsibility to other generations of humans, but also, we don't have the power to destroy life, but we have the power to really screw it up.
Victoria Wicks: Peter Larson says he plans to return to the Hell Creek Formation this summer. And Robert DePalma intends to return to the Tanis site. All three paleontologists note that federal protections for fossils exist on public land, but not on private. Sally Shelton says finding a protected fossil in the path of construction can result in expensive delays, but she has known of construction crews who became excited by a fossil discovery and help to extract it safely. The key is having someone on site who knows how to spot it before it's destroyed. For South Dakota Public Broadcasting, I'm Victoria Wicks in Western South Dakota.
Victoria Wicks asked TC Energy if there is a paleontologist monitoring for fossils at current construction sites, particularly on Bureau of Land Management property at the border. She did not receive an answer to that question.
Click on the link below to read the research paper on the Tanis site, titled "A seismically induced onshore surge deposit at the KPg boundary, North Dakota" by Robert A. DePalma, et al.
To learn more about the Western Interior Seaway in a very cool interactive map put together by the Museum of Geology at the SD School of Mines and Technology, click here: