Last Day of the Dinosaurs: Discoveries at Tanis
Scientists have uncovered a fossil site in the United States that offers a rare glimpse into the final moments of the dinosaurs. A fragment of the asteroid that struck Earth 66 million years ago may have been found within amber, a find NASA has described as mind blowing. This location, part of the Hell Creek formation in North Dakota, preserves relics from the catastrophe that ended the age of the dinosaurs.
The site has yielded a variety of remarkable finds. Fossils include fish that appear to have consumed debris stirred up by the impact, a turtle preserved in a stick, and a leg that may belong to a dinosaur that witnessed the meteor strike.
The story behind these discoveries is told in a documentary titled Dinosaur Apocalypse, broadcast on the PBS program Nova, featuring naturalist Sir David Attenborough and paleontologist Robert DePalma, as reported by CNN.
DePalma, a graduate researcher at the University of Manchester and an adjunct professor in the Department of Geosciences at Florida Atlantic University, began fieldwork at Tanis in 2012.
The landscape is now harsh and barren, a stark contrast to its late Cretaceous appearance when the American Midwest was a swampy forest. An inland sea once linked what is now the Gulf of Mexico to Canada, shaping a very different chapter in the region’s geology.
Remains recovered on site
The Tanis site lies more than 3,000 kilometers from the Chicxulub crater, yet early explorations suggested a clear link to the mass extinction event. The area is home to thousands of remarkably preserved fish fossils buried by displaced sediments from a large body of water generated by the impact. The inland sea channel receded after the event, and the water may have moved with seiche-like activity rather than a slow, hours-long wave that reaches land. The rapid sequence of events, it seems, unfolded in a flash.
Analyses indicate the catastrophe happened quickly. Researchers believe the fish died within an hour of the asteroid’s impact, not as a consequence of the later wildfires or a prolonged winter. Tiny spheres of molten rock, formed when material blasted from the crater and cooled into glass, were found embedded in fish gills. The data also suggest the asteroid struck in spring, adding a seasonal context to the event.
As DePalma described, the evidence accumulated like the clues in a detective story. The investigation unfolds step by step, offering a rich resource for scientific study and a clearer narrative of what occurred immediately after the impact.
Many of the latest discoveries shown in the documentary have not yet appeared in journals, but the footage provides a vivid record of the Tanis site and its significance.
Tanis as the “Last Day” Site
The most striking aspect is how the remains seem to correspond to the exact day of the asteroid fall. Michael Benton, a vertebrate paleontologist at the University of Bristol who advised on the documentary, notes that the fossil bed appears to document the dinosaurs’ final day. Some experts once disagreed about timing, but the consensus now leans toward a direct link to the Mexico impact event.
Glazed spheres that announced the asteroid’s traces are preserved in clay by millions of years of geological processes. Some spheres, however, were found trapped in tree resin on a trunk and preserved in amber, offering a rare time capsule from the event. In amber, the spheres remained intact, untouched by the surrounding sediment, a remarkable snapshot of another moment in time.
DePalma called the amber findings like opening a time capsule and saving a sample from the impact site for science. Researchers recovered several small, unmelted rock fragments inside glass spheres. Many of these are calcium-rich and likely originate from limestone beneath what is now the Yucatán region.
In contrast, other fragments exhibited a very different composition, rich in chromium, nickel, and other elements associated with meteorites. The preliminary analysis suggests a cosmic origin, highlighting how a tiny fraction of the colliding asteroid could leave a lasting record on Earth.
Jim Garvin, a chief scientist at Goddard Space Flight Center, remarked that the discovery underscores how a minuscule amount of cosmic material could be preserved and studied for generations, offering a tangible link to the asteroid that shaped Earth’s history.
Leg of a Dinosaur on Impact Day
Another notable discovery in the documentary is a nearly perfectly preserved dinosaur leg with skin. The Thescelosaurus, a small plant eater, appears to have died on the same day as the asteroid impact. The preservation of soft tissues indicates the body did not have time to decay before burial in sediment.
The possible proximity of death to the time of impact has sparked discussions about the sequence of events on that day. The leading hypotheses consider whether the dinosaur perished in nearshore waters or just before the collision, with the timing so tight that decay did not occur.
For further context, the investigation into this site continues to provide a striking blend of petrographic, paleontological, and geological evidence, shedding light on the events that followed the impact.
Note: The documentary’s findings are part of a broader effort to understand the end-Cretaceous extinction and how diverse life forms met their demise in that dramatic moment in time.