Geologic Findings Undermine Theories of Permian Mass Extinction Timing

Mar 02, 2009
The Karoo Basin in South Africa holds the world's best record of the Permian Mass Extinction. Credit: Robert Gastaldo, Colby College

(PhysOrg.com) -- New scientific findings by geologist Robert Gastaldo of Colby College in Waterville, Maine, and colleagues call into question popular theories about the largest mass extinction in Earth's history.

A paper reporting the results by Gastaldo, South African scientist Johann Neveling, and two 2008 Colby undergraduate students, C. Kittinger "Kit" Clark and Sophie Newbury, appears in the March 2009 issue of Geology.

Tens of millions of years before dinosaurs roamed Earth, their ancestors were all but eliminated in a catastrophic event called the Permian Mass Extinction. The Permian period extended from 299 to 252.6 million years ago.

"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," says H. Richard Lane, a paleontologist and program director in the National Science Foundation (NSF)'s Division of Earth Sciences, which funded the research.

"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."

Ideas about the event's impact on land animals and plants are based largely on records in the Karoo Basin in central South Africa, where the best fossil records from that time are found, and where Gastaldo and his students have worked since 2003 with funding from NSF.

Earlier analysis of the rock record by other scientists working in South Africa led them to hypothesize about the nature, scope and timing of the mass die-off of prehistoric amphibians and reptiles.

They claimed that one unique sedimentary layer in the Karoo Basin overlies fossils of the last reptiles of the Permian period (synapsids, including the genus Dicynodon).

This layer has been dubbed "the dead zone" because of its absence of fossil remains.

This dead zone was thought to be synchronous in time and space, marking the event across southern Africa and as far away as Antarctica.

Now Gastaldo and co-authors report that they have found conflicting stratigraphic evidence in the Karoo Basin.

They discovered that this dead zone layer, or event bed, is not found at the same physical position in the rock record at all places, even across the immediate landscape where it was first described.

As such, it is not a reliable marker of the mass extinction of terrestrial animals, Gastaldo says.

Within one kilometer, just across the valley from the site where it was first described, the layer occurs lower in the rock record by eight meters (more than 25 feet).

Several hundred kilometers away, at Lootsberg Pass, reptile fossils occur above the layer rather than below it, further undermining the credibility of the zone as a marker of the mass extinction of animals at the end of the Permian.

Gastaldo says that the research proves that "there is no evidence to support a terminal extinction event in the record of the Karoo Basin, based on the criterion of an unique event bed or dead zone."

Provided by NSF

Explore further: Better forecasts for sea ice under climate change

add to favorites email to friend print save as pdf

Related Stories

Rocks can restore our climate... after 300,000 years

Jul 09, 2013

(Phys.org) —A study of a global warming event that happened 93 million years ago suggests that the Earth can recover from high carbon dioxide emissions faster than previously thought, but that this process ...

Sea life facing major shock

Aug 21, 2012

(Phys.org) -- Life in the world's oceans faces far greater change and risk of large-scale extinctions than at any previous time in human history, a team of the world's leading marine scientists has warned.

Global extinction: Gradual doom is just as bad as abrupt

Feb 03, 2012

A painstakingly detailed investigation shows that mass extinctions need not be sudden events. The deadliest mass extinction of all took a long time to kill 90 percent of Earth's marine life, and it killed ...

Seeking a pot of geological gold

Dec 16, 2011

Researchers are moving a step closer to solving one of the greatest murder mysteries of all time. It happened roughly 200 million years ago, marking the boundary between the Triassic and Jurassic periods, ...

Recommended for you

Better forecasts for sea ice under climate change

7 hours ago

University of Adelaide-led research will help pinpoint the impact of waves on sea ice, which is vulnerable to climate change, particularly in the Arctic where it is rapidly retreating.

"Ferrari of space' yields best map of ocean currents

15 hours ago

A satellite dubbed the "Ferrari of space" has yielded the most accurate model of ocean circulation yet, boosting understanding of the seas and a key impact of global warming, scientists said Tuesday.

Researcher studies deformation of tectonic plates

18 hours ago

Sean Bemis put his hands together side by side to demonstrate two plates of the earth's crust with a smooth boundary running between them. But that boundary is not always smooth and those plates do not always ...

User comments : 3

Adjust slider to filter visible comments by rank

Display comments: newest first

jonnyboy
1.7 / 5 (3) Mar 03, 2009
righhhhhhhhhhhhhhhhhttttttttttttttttttttt

everyone else that has studied this is wrong and only this one professor is right
out7x
2.3 / 5 (3) Mar 05, 2009
On the contrary, there is much evidence in the Karoo. Read this book. "Extinction", by Erwin.
Velanarris
not rated yet Mar 15, 2009
righhhhhhhhhhhhhhhhhttttttttttttttttttttt

everyone else that has studied this is wrong and only this one professor is right

It's like steady state theory, there's strong evidence against it, but everyone accepts it as truth. That doesn't necessarily make it true.

This new evidence is certainly interesting.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.