As the site of an ancient meteor impact, which took place 1.85 billion years ago, the Sudbury area held a special significance to geologists John Slack and Bill Cannon before they began working on their most recent research.
“In the community of impact geologists, it’s one of the most famous places on earth,” Cannon said. But the Reston, Virginia-based U.S. Geological Survey employees are now hypothesizing that the meteorite impact set off a chain of “extraordinarily violent” events, which caused a worldwide change in geology, and even a possible impact upon the evolution of early life.
They published research last fall in the publications Geology and GSA bulletin, which states that the meteorite impact was responsible for a change in ocean conditions across the planet.
Cannon, who has spent much of his career studying the geology of the Lake Superior region, and Slack, an expert in ancient seafloor mineral deposits, said the meteorite impact caused tsunamis, which mixed oxygen into the ancient oceans. Before the meteorite impact, the bottom layer of water in the ocean was high in dissolved iron and low in oxygen, they explained. This environment allowed for the deposition of banded iron formations, which can be seen today in the Lake Superior region, in Michigan and Minnesota.
However, after the meteorite impact, these iron deposits stopped forming — worldwide — for about 500 or 600 million years. Work done by Cannon, along with geologists in Thunder Bay, has shown that the rock thrown as a result of the Sudbury meteorite impact — called ejecta — covers these iron formations in the Lake Superior region.
“I think the concern of a lot of other workers is that our model proposes a geologically instantaneous end for the deposition, globally, of these giant iron formations,” Slack said. “Most other workers have inferred protracted processes is earth’s history — heat from mantle, changes in the atmosphere, changes in the nature of continents — that took place over 10s of millions of years.”
Although they stressed they are not experts in this area of research, Slack and Cannon also propose the oxygenation of the ancient ocean, after the impact, may have caused more complex life forms to develop. They included a paragraph at the end of their article in the Geology journal, which speaks about this hypothesis.
“In a very general sense, it’s reasonable to propose that the Sudbury impact did have some significant influence on life.
You’re probably familiar with the giant meteor impact that killed the dinosaurs and thousands of other species,” Cannon said. “The Sudbury impact was somewhat larger than that dinosaur-killing event. It seems to me to be very likely that it has some impact on the survival of some species, and perhaps the evolution of some species shortly after.”