Scientists wonder if it actually happened

Mar 3, 2009 14:40 GMT  ·  By
A chart showing how marine species died throughout the course of history - the middle, largest spike is the Permian-Triassic boundary
   A chart showing how marine species died throughout the course of history - the middle, largest spike is the Permian-Triassic boundary

It's widely accepted in the scientific community that a massive extinction event took place on Earth between the Permian and the Triassic periods, wiping up almost 90 percent of both marine and land species and driving the ancestors of dinosaurs to the brink of extinction. Now, a team of researchers is seeking to invalidate this hypothesis, by hitting at its very core, the Karoo Basin in South Africa.

At this location, the layers of soil offer one of the most clear windows into our planet's agitated past, and other researchers have mostly used evidence gathered here to support their theories. They say that, among the sediments, a “dead zone” exists, an area where no fossils can be found. They add that this is a clear indicator of the fact that a mass extinction event occurred at that time, which killed off most of the animals on Earth.

However, Waterville, Maine-based geologist Robert Gastaldo, from the Colby College, and his colleagues believe that this line of reasoning is false, simply because the so-called “dead zone” cannot be verified anywhere else in the world. That is to say, if a global event were to have happened, then it's traces would have remained embedded in all the soil layers of virtually all regions of the globe. Still, nowhere in the world where the Maine team has looked has there been any evidence of the “dead zone” at the designated depth. Or anywhere near that depth, for that matter.

But, in order to convince the international scientific community of this, the team has started digging in the Karoo Basin. It concludes in the March 2009 issue of the journal Geology that there are no conclusive facts to prove that the Permian-Triassic extinction actually took place when established, or whether the impact it had on the species of the time was that harsh.

“The Permian-Triassic boundary marks the greatest extinction event in Earth's history, with significant loss of biodiversity both on land and in the oceans. Until this study, it was believed that the event was marked by unique rocks traceable across southern hemisphere continents. This research calls into question whether the extinction event is actually constrained in the geologic record on land,” the National Science Foundation (NSF) Division of Earth Sciences' Paleontologist and Program Director H. Richard Lane shares. He has been the one to supply the funds for the new research.