View Full Version : The Day the Dinosaurs Died

03-30-2019, 04:51 PM
"Sixty-six million years ago, a massive asteroid crashed into a shallow sea near Mexico. The impact carved out a 90-mile-wide crater and flung mountains of earth into space. Earthbound debris fell to the planet in droplets of molten rock and glass. Ancient fish caught glass blobs in their gills as they swam, gape-mouthed, beneath the strange rain. Large, sloshing waves threw animals onto dry land, then more waves buried them in silt. Scientists working in North Dakota recently dug up fossils of these fish: They died within the first minutes or hours after the asteroid hit, according to a paper published Friday in Proceedings of the National Academy of Sciences, a discovery that has sparked tremendous excitement among paleontologists. The Hell Creek fossils represent “the first mass death assemblage of large organisms anyone has found” that sits at the K-Pg boundary, study author Robert DePalma said in a statement.
"DePalma, a doctoral student at the University of Kansas, began excavating the site at North Dakota’s Hell Creek formation in 2013. Since then, DePalma and other paleontologists have found heaps of fossilized sturgeon and paddlefish with glass spheres still in their gills. They found squidlike animals called ammonites, shark teeth and the remains of predatory aquatic lizards called mosasaurs. They found dead mammals, insects, trees and a triceratops. They found foot-long fossil feathers, dinosaur tracks and prehistoric mammal burrows. They found fossilized tree gunk called amber that had captured the glass spheres, too.

"The site has “all the trademark signals from the Chicxulub impact,” Bralower said, including the glass beads and lots of iridium. In the geologic layer just above the fossil deposit, ferns dominate, the signs of a recovering ecosystem. “It’s spellbinding,” he said. About 3 in 4 species perished in what is called the Cretaceous-Paleogene extinction, also known as the K-Pg event or K-T extinction. The killer asteroid most famously claimed the dinosaurs. But the T. rex and the triceratops were joined by hordes of other living things. Freshwater and marine creatures were victims, as were plants and microorganisms, including 93 percent of plankton. (A lone branch of dinosaurs, the birds, lives on.)


Greater detail here: https://www.newyorker.com/magazine/2019/04/08/the-day-the-dinosaurs-died