When the meteor smashed into waters near what is now Mexico’s Yucatán Peninsula, it left a giant crater known as Chicxulub and prompted upheavals thousands of miles away, including what is now North Dakota. Within hours and perhaps minutes of the titanic collision, sea creatures were swept inland by tsunamis and earthquakes, tossed together and deposited with a diverse array of landlocked life, including trees, flowers and vanished types of freshwater fish.

Image Robert A. DePalma, a paleontologist at the Palm Beach Museum of Natural History and a graduate student at the University of Kansas. He has mined a fossil site in North Dakota secretly for years. Credit... Robert DePalma/University of Kansas

The jumble was swiftly entombed, and exquisitely preserved. Permeating the deposit were tiny spheres of clay and glass, known as tektites, which formed as molten rock, ejected by the impact, showered from the sky.

In the paper, the researchers argue that the fossil bed captures the Chicxulub impact’s immediate ramifications for life on Earth. It appears to be the best-ever snapshot of that day, one that advances the scientific understanding of “the full nature and extent of biotic disruptions that took place,” the authors write.

The lead researcher, Robert A. DePalma, is a curator of paleontology at the Palm Beach Museum of Natural History, in Florida, as well as a graduate student at the University of Kansas. Thirty-seven years old, he was granted access to the rich fossil bed by a rancher in 2012, then mined it secretly for years. His efforts are detailed in an article in The New Yorker that was posted online on Friday.

Gradually, Mr. DePalma shared his findings with top scientists, some of whom have now joined him as co-authors. They include Walter Alvarez, a geologist at the University of California, Berkeley, who pioneered the idea decades ago that the dinosaur extinction was the result of such a cosmic impact.