Single impact might have caused dinosaur extinction
Published Dec. 8, 2006
As a kid, geology professor Ken MacLeod's favorite dinosaur was the triceratops.
"But now it is the little southern ones coming out of China," he said.
That dinosaur is known as the Microraptor, which has feathers on both its arms and its legs, he said, and is counted as a four-winged dinosaur.
"Finding dinosaurs with feathers is a big deal," he said. "And finding one with four wings is fun and unusual."
MacLeod hasn't just found dinosaurs with feathers, though.
He might have found further evidence for what wiped out all the dinosaurs nearly 65 million years ago.
He had found formidable evidence that might help to answer the age-old question of how the dinosaurs became extinct.
MacLeod said his four-person team's research provides evidence that a single impact caused the mass extinction.
The project began after samples were discovered during a scientific cruise.
The samples were collected January and February of 2003, MacLeod said.
"I had the samples in hand by that fall," he said.
The researchers who co-authored the report with MacLeod were Donna Whitney from the University of Minnesota, Brian Huber of the Smithsonian National Museum of Natural History and Christian Koeberl of the University of Vienna. MacLeod and his team were able to begin working on the samples in detail in July, August and September of that same year.
Research took place all over the globe. MacLeod did a number of measurements and descriptions here at MU.
Other portions of the research took place at the Smithsonian in Washington, D.C., the University of Minnesota and in Vienna, Austria. The samples were radiated in Hungary.
According to the team's report, the samples were obtained from Demerara Rise, located about 4,500 kilometers from the site of the impact, which is at Chicxulub on the Yucatan Peninsula in Mexico.
The samples from Demerara Rise were "far enough away (and perhaps sheltered by the curve of northern South America) to have been relatively unaffected by impact-introduced waves."
The report also states, "The sedimentological, geochemical and paleontological record across the K-T boundary interval at Demerara Rise is remarkably unambiguous."
The K-T boundary is also known as the Cretaceous-Tertiary boundary, and is a period of time between those two time periods that represents the time when dinosaurs became extinct.
"I think what's unique about our samples is that they're not very complicated," MacLeod said. "All the parts are there in one sight. While the hypothesis is out there, this is the cleanest example of the rock record at the K-T boundary."
The conclusions are based on reading the rock record, he said.
"It's really quite a straightforward set of rock, from oldest to youngest, and bottom to top," he said. "We're looking at what the rocks are and what fossils are in them with that bottom to top giving us a time."