Posted on 11/07/2007 4:47:01 AM PST by Renfield
A series of gargantuan volcanic eruptions may have ended at nearly the same time that the dinosaurs went extinct, a new study shows.
The find bolsters a controversial theory that massive volcanism contributed to the global catastrophe known as the K-T extinction, which wiped out the dinosaurs and many of Earth's other organisms 65 million years ago.
Gerta Keller, a Princeton University paleontologist, presented the new research last week at a meeting of the Geological Society of America in Denver, Colorado.
She found that underwater portions of the ancient lava flows, known as the Deccan Traps, contained marine fossils only of species known to have existed after the extinctions.
In other words, all of the marine sediments that built up on the lava flows came from after the extinction.
"So we can say that the flows, which mark the end of the main phase, of the Deccan eruptions ended near the K-T mass extinctions," she said.
Worldwide Effects
For years, Keller and a few other scientists have suspected that the Deccan Traps played a role in the global catastrophe.
The eruptions would have been on a scale that dwarfed anything ever experienced by humans, burying parts of western India in nearly 12,000 feet (3,500 meters) of volcanic rock, they say.
The effects worldwide would have been even worse, Keller said. Each of the flows would have released vast quantities of climate-altering gases—up to ten times as much as were produced by the famed Chicxulub asteroid impact in Mexico's Yucatan peninsula. Most scientists believe the Chicxulub impact is the major cause of the dino die-off.
The Deccan Traps devastation would also have occurred quickly.
"Each of these megaflows could have been formed in weeks, months, or years," Keller said, citing a study by French scientists.
Eighty percent of the lava was produced during a single pulse of eruptions, she added.
But prior studies, based on radioactive elements contained in the lava, only showed that the lava flows and the extinctions occurred within about 300,000 years of each other.
So Keller followed a finger of lava across India and down an ancient river valley that channeled it all the way to the Gulf of Bengal, more than 900 miles (1,500 kilometers) from its source.
Layers of volcanic rock from the Deccan Traps eruptions make a telltale striated pattern in western India.
Some of that lava eventually wound up underwater and slowly accumulated marine sediments containing the fossils of plankton. But none contained species killed off during the K-T extinction, suggesting the flows ended around that time.
The correlation isn't perfect, Keller said. It's always possible that the lava flow ended slightly after the extinction—or even a few tens of thousands of years before—because the geological record isn't complete.
But, she added, "if someone wants to say that this kind of thing has nothing to do with [the] mass extinction—even if it ended 100,000 years earlier—they're out of their mind."
Still Open to Debate
Keller's arguments against Chicxulub as the lone dino-killer have long been contentious, and this one is no exception.
Greg Ravizza, a geochemist at the University of Hawaii who has studied seawater changes related to the Deccan volcanism, argued that Keller is focusing too strongly on when the volcanism ended.
"Keller and co-workers prefer an interpretation that concentrates the bulk of the Deccan volcanism very close to the K-T boundary," he said by email.
But the key question is when the major pulse of Deccan volcanism started, he pointed out.
Furthermore, he said, the lava flows Keller studied weren't even recognized as part of the Deccan volcanism until recently and are geographically isolated from the vast majority of the Deccan Traps.
"Whether or not the upper and lower traps at Rajahmundry [the location studied by Keller] can be claimed to fully represent the two largest and most extensive Deccan volcanic eruptions is still open to debate," Ravizza said.
Meanwhile, Keller's argument that the Deccan Traps eruption forced major climate change may have additional support.
Anne-Lise Chenet is one of the scientists whose radioactive decay studies helped confirm that the Deccan volcanism occurred within a few hundred thousand years of the K-T boundary.
She is also co-author of a study, soon to appear in the Journal of Geophysical Research Letters, that examined the volcanic gases emitted by the flows.
"The amount of sulfur dioxide emitted by each volcanic event ... [leads us] to reconsider the effect of volcanism ... on the climate and environment," she said by email.
Dinosaur ping.
Photo in the News: Pre-Dino Amphibian Body Casts Found
http://news.nationalgeographic.com/news/2007/10/071030-amphibian-fossil.html
October 30, 2007—An undergraduate student digging through a collection of fossils in a Pennsylvania museum recently found beautifully preserved full-body impressions of foot-long (30-centimeter-long) salamander-like creatures that lived 330 million years ago.
The fossils, top, don't contain bones. But that's good, said Spencer Lucas, curator of the New Mexico Museum of Natural History and Science, who presented the find today at a meeting of the Geological Society of America in Denver, Colorado.
That's because bones are merely skeletons. "From the cast of the body, you can see the actual shape of the body and can see what the texture of the skin was like," Lucas said in a telephone interview.
"There's never been a body impression of this kind of amphibian found before," he added.
The imprints reveal that the animal had webbed feet and that its skin was smooth, not scaly or armor-plated, as seen in an artist's depiction (bottom).
Also, the fact that two of the salamanders are aligned head-to-toe might indicate courtship behavior similar to that engaged in by modern salamanders. But "that's very speculative," Lucas said.
The fossil had been in the museum since before World War II, until David Fillmore, an undergraduate at Kutztown State University in Pennsylvania, looked at it as part of a senior research project.
"It's a classic case in point that a lot of these collections scattered around the nation have important discoveries waiting to be made in them," Lucas said.
—Richard A. Lovett
I thought the dinosaurs died from their own 'Methane Exhaust'. ... or is that not the 'Theory-de-Jour'. /s
Dinosaur Deaths Outsourced to India?
EurekAlert | 10/30/07 | Gerta Keller, etal
Posted on 10/30/2007 4:31:46 PM EDT by crazyshrink
http://www.freerepublic.com/focus/f-news/1918560/posts
Volcanic Eruptions, Not Meteor, May Have Killed The Dinosaurs
Science Daily | 10-30-2007 | Geological Society of America.
Posted on 10/31/2007 6:08:40 PM EDT by blam
http://www.freerepublic.com/focus/f-news/1919180/posts
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The fossil had been in the museum since before World War II, until David Fillmore, an undergraduate at Kutztown State University in Pennsylvania, looked at it as part of a senior research project. "It's a classic case in point that a lot of these collections scattered around the nation have important discoveries waiting to be made in them," Lucas said.It's more like a classic case of nearly 70 year old data having been ignored until now. Must have undermined the dominant paradigm.
Whole communities of ape-like creatures may have been killed in volcanic disasters that struck East Africa 18 million years ago... the once active volcano Kisingiri... contained fossils of what is believed to be a forerunner of humans called Proconsul... they may have been caught by a pyroclastic flow... the abundance of the hominoid fossils may represent "death assemblages" - whole populations wiped out simultaneously by "glowing cloud" eruptions.
Dinosaurs died out because they went on biting while the mammals were learning to box.
Note: this topic is from 11/07/2007. Adding to the list, not pinging.
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