Researchers of a new study find evidence that the “killing field” at a site in North Dakota is linked to the asteroid that killed the dinosaurs 66 million years ago. This is the first fossil graveyard of large organisms linked to the impact at the end of the Cretaceous period.
In 2013, paleontologist Robert DePalma unearthed a fossil graveyard at a digging site in the Hell Creek Formation. There, he discovered the fossilized remains of fish stacked one over the other, along with conifers, burned tree trunks, dead mammals, insects, mosasaur bones, marine microorganisms, marine cephalopods, and the partial remains of a triceratops.
Even back then, he had a suspicion that this clumping of dead creatures in one area may have been a result of the asteroid impact that wiped out the dinosaurs.
“At no other K-T boundary section on Earth can you find such a collection consisting of a large number of species representing different ages of organisms and different stages of life, all of which died at the same time, on the same day,” said DePalma.
Iridium And Tektites
All around the world, rocks that are 66 million years old tend to have excess iridium in them, possibly a result of the asteroid impact since iridium is rare on Earth but is common in asteroids and comets. Then there are also tektites, which are small glass beads that rained down from the melted rock.
What’s interesting about the fossil discovery is that while both sediment layers have excess iridium, only the lower layer had tektites, likely from an inland moving force. What this means is that the fossils were a result of two different events.
The first one resulted in the lower layer, which happened mere hours after the impact, and the second one is the upper layer later on when the dust was already settling after the impact.
In addition, some of the fish’s gills had glass beads in them, suggesting that they were directly impacted by the rain of glass beads.
Seiche Mass Death
According to the researchers, this suggests that the deaths occurred as a result of at least two seiches or standing waves that occurred within minutes after the impact, perhaps 20 minutes apart, in the inland sea that is now North Dakota.
The hypothesis is that hundreds, if not thousands, of fish were tossed onto a sand bar as a result of the first wave, and there, they were pelted by the glass beads falling from the sky. About 10 to 20 minutes more of the glass rain and the second wave came in, burying the fish with gravel, sediment, and sand for 66 million years.
First Deaths From The Asteroid Impact
Basically, the discovery is evidence of the first deaths that occurred right after the impact. In a way, it is like a snapshot of the exact day when the asteroid hit the Earth and sparked the dinosaur extinction and the end of an era.