fossil graveyard

A “Cretaceous death pit” doesn’t sound like much fun and for the dinosaurs and some vegetation of the era, it wasn’t. Also described as a “fossil graveyard,” this fossil bonanza was identified in North Dakota. When scientists evaluated it, they determined it could help solve one of the world’s most enduring unsolved mysteries. You know, the age-old question of “What killed the dinosaurs?” This link could eventually help scientists solve that question once and for all, along with determining what happened on earth right after the Chicxulub meteoric impact thought to have set extinction in motion. Here’s how:

Building On What We Know

Paleontologists are intrigued by the results of a 2018 study published in April 2019 in the Proceedings of the National Academy of Sciences of the United States of America. All involved are hoping the analysis of a fossil graveyard in North Dakota will lead to a better understanding of the global environmental and biotic collapse of the Cretaceous– Paleogene dinosaur extinction.

The site is part of the Hell Creek Formation and earned the nickname Tanis as a nod to the lost Egyptian city. According to a New Yorker article that came out a bit before the academic piece, the Tanis riches include a smorgasbord of fossils, among them teeth and hatchling remnants from HCF dinosaur groups. The groups include standout dinosaurs of the type that have been thrilling kids and intriguing paleontologists for centuries, like therapods, which include Tyrannosaurus, ankylosaurs, and ceratopsians, which include Triceratops. Tanis also turned up some extinct mollusks and fragmented marine fossils, including teeth from ancient sharks, reptiles known as mosasaurs. The New Yorker also included news of foot-long feathers from the sedimentation on the site and an egg with a preserved embryo inside.

Astonishing on its own, this goulash of fossils in the sediment on a private ranch also makes a link lacking in previous research efforts: It establishes a high-resolution chronology of the immediate aftereffects of the Chicxulub impact event in the Western Interior. Earlier work has been extensive, but this is the first evaluation of an entire ecosystem clobbered by the impact. The study’s authors hope their report of marine and terrestrial sedimentation that corresponds to the Chicxulub meteoric impact will advance scientific understanding of how debris was ejected and life on earth disrupted in the first moments post-impact.

How Chicxulub Ended An Era

If the details of the earth’s many time divisions have faded since eighth grade Earth Science, it’s worth remembering that the dinosaurs roamed during the Mesozoic Era, and the Cretaceous Period was the final segment of that era. What brought down the curtain? Most scientists agree there was a minor extinction event that made the Jurassic Period halt some 145.5 million years ago, followed by a be-all, end-all Cretaceous-Paleogene (K-Pg) extinction event about 65.5 million years ago. Plots of the Land Before Time movies notwithstanding, the general consensus is that the Chicxulub meteoric impact ended the Cretaceous period and signaled the onset of planet-scale climate change that resulted in mass extinction.

When this massive asteroid slammed into the Yucatan peninsula, where you’d find Mexico today, it took the last of the non-avian dinosaurs with it. Other casualties included about 75 percent of the earth’s vegetation, numerous brachiopod families and sea sponges, and a wealth of shark species. For whatever reason, survivors included such life forms as turtles, frogs, and salamanders. Starfish and snails also persevered, along with birds.

How Tanis Reveals Life Right After The Asteroid

Scientists have proposed many different results of the Chicxulub impact that might have caused this wide-scale extinction, from sun-blocking debris and smoke to climate shift to impact-induced volcanism. It’s generally accepted that the asteroid tore a 50-mile wide chunk from the earth’s crust and sent a flash of molten earth up and out at amazing velocities. This also produced tektites, tiny glass blobs that rained down after impact like hail on crops for about 45 minutes. Evidence of tektites in the Tanis sediments may be a crucial clue linking the fossil mishmash to the Chicxulub impact.

A couple of other clues also indicate that the creation of this Tanis fossil mother lode happened with the Chicxulub event. According to the study authors, Acipenseriform fish were densely packed in the deposit, for example. They clearly “were buried by an inland-directed surge that inundated a deeply incised river channel,” the article states. “Although this deposit displays all of the physical characteristics of a tsunami runup, the timing (less than an hour post-impact) is instead consistent with the arrival of strong seismic waves from the magnitude Mw ∼10 to 11 earthquake generated by the Chicxulub impact.”

Enough Fossils For Many More Findings

Paleontologists quoted by both National Geographic and the New Yorker did indicate that the studies claims would need more work before they’d be widely accepted. Some paleontologists thought that opening the Tanis research site to more research and allowing more access to its materials would be a much-needed next step.

Whether or not that happens, Lead study author Robert DePalma also told National Geographic that the dinosaur-obsessed public and his fellow researchers could expect a few more scientific studies from this find. “It essentially stockpiled the rarest and most poorly represented things in [the rock formation] in one deposit that we can study for decades—and that’s without even including the impact scenario,” according to DePalma, a University of Kansas Ph.D. student and curator at the Palm Beach Museum of Natural History.