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Dinosaurs Met End Before K-T Collision
Science Daily ^ | 15 Jan 2003 | Penn State

Posted on 01/17/2003 11:09:44 PM PST by pepsionice

Dinosaurs Experienced Climate Changes Before K-T Collision

Climate change had little to do with the demise of the dinosaurs, but the last million years before their extinction had a complex pattern of warming and cooling events that are important to our understanding of the end of their reign, according to geologists.

"The terrestrial paleoclimate record near the K-T is historically contradictory and poorly resolved," says Dr. Peter Wilf, assistant professor of geosciences at Penn State. "In contrast, the resolution of K-T marine climates that has emerged over the last 10 years is excellent. Our work brings the terrestrial record up to speed so that we can look for global climate events that occurred for both land and sea."

Wilf worked with Kirk R. Johnson, curator of paleontology, Denver Museum of Nature & Science, who provided the data on land plant fossils and Brian T. Huber, curator of Foraminifera, National Museum of Natural History, Smithsonian Institution, who provided the marine data.

An extraterrestrial object that impacted the Earth near the Yucatan in Mexico 65.51 million years ago doomed the dinosaurs and 70 percent of the Earth's other species, vaporizing itself and the surrounding rocks and throwing enough ash, soot and debris into the atmosphere to effectively stop photosynthesis worldwide. This impact radically altered the natural progression of evolution. The time of the impact is called the K-T boundary and marked the end of Cretaceous Period and the beginning of the Tertiary Period.

"It could be argued that we are still recovering from that impact and the mass extinctions of dinosaurs, mammals, insects, plants and sea life that it caused," says Wilf, who worked on this project at the University of Michigan before coming to Penn State. "For example, not only the dinosaurs, but also 80 to 90 percent of the Cretaceous plant species, including all the dominant species, disappeared."

According to Wilf, there is a lingering minority argument that the K-T extinction was caused by climate change, but the research team's results, published in a recent issue of the Proceedings of the National Academy of Sciences, both document the climate changes and show that they were not the principal cause.

Wilf, Johnson and Huber first worked to create a finely resolved terrestrial temperature record, based on plant fossils, and then correlated that record with the existing marine records.

Plant fossils from the one million-year period before the extinction that are abundant and well preserved in a fine time sequence are found only in New Mexico and North Dakota. Of the two, the North Dakota sites are comparably much more intensively collected and studied and enabled Johnson to collect 22,000 plant fossils of more than 300 fossil plant species.

"Only in the last year, with the publication of an entire volume filled with new research results on the Hell Creek Formation in North Dakota, can we do this work and tie the plant fossil record there to actual dates in millions of years rather than relative dates," says Wilf. Johnson is a co-editor and contributor for the Hell Creek volume.

Fossils can be dated relatively by their position in the stratigraphy or layers of sediment using a simple rule. In undisturbed layers, the oldest fossils are in the lowest layers and the most recent fossils are in higher levels. Tying relative dates to real dates is not easy, especially keeping within the 100,000 year sensitivity available in the marine record, which comes from the scientific results of the ocean drilling program.

Luckily, the K-T extinction occurred during a short interval in the Earth's magnetic pole reversals. Periodically, the Earth's poles switch polarity making North negative and South positive. Eventually, another switch occurs making North positive and South negative. A record of the Earth's paleomagnetism is recorded in the rocks as they are laid down.

"Three hundred and thirty-three thousand years before the extinction, a pole reversal occurred," says Wilf. "Two hundred and seventy thousand years after the extinction, another reversal occurred."

Because the researchers have three datable points --the two reversals and the K-T impact – they could attach ages to the layers and the fossils within and correlate the terrestrial and marine data at much finer resolution than ever before.

Simply equating the layers, however, was not enough. The researchers needed to estimate the temperature of the environment in which each fossil grew. For the plants, this turned out to be simple, using a method first developed in 1915 that is still widely used today.

Modern forests have two types of trees, those with toothed leaves and those with smooth leaves. The cooler the climate, the higher the percentage of species with toothed leaves.

"The presence of palm species also suggests a warm climate as these plants cannot survive the ground freezing," says Wilf.

The researchers found from the plants that the long, slow cooling that occurred for millions of years of the Late Cretaceous was broken by a warming event that began about 66 million years ago and peaked 300,000 to 100,000 years before the K-T collision. The temperatures then returned to baseline just before the collision and stayed nearly constant before and after the collision. The plant record agreed strongly with the marine data, which comes from ocean coring projects in the South Atlantic, Antarctica and off the shores of New Jersey and Florida, and is based on the oxygen isotope ratios in the skeletons of marine-shelled micropredators called Foraminifera. The colder the water, the more of the heavier oxygen isotope is incorporated in the calcium carbonate of the shells. The sediments that entomb the forams also record the paleomagnetic reversals around the K-T.

Because the marine data come from four different locations and the terrestrial data from a fifth, the warming and cooling trends seem global, according to Wilf. The marine data also show that warm water forams migrated from the tropics as far as New Jersey and Antarctica.

While the mean annual temperature in North Dakota today is 43 to 45 degrees Fahrenheit, during the warmest part of the warming episode, the mean annual temperature was from 65 to 68 degrees Fahrenheit. The North Dakota site was then at the same latitude as Quebec City, Canada, and not only palm trees, but alligators and turtles thrived too.

"The K-T impact affected the Earth's living things severely and dramatically, but the climate changes right before the impact, by comparison, did not," says Wilf. "Understanding the climate and vegetation before the impact gives us insight into what kind of world the meteorite struck, and shows us that it was warming, cooling, lushly forested and otherwise functioning the way it always has done. The dinosaurs were well adapted to global warming and cooling, but not to giant speeding rocks from space."

The American Chemical Society, National Science Foundation and Smithsonian Institution funded this research.


TOPICS: Miscellaneous
KEYWORDS: climate; crevolist; dinosaurs
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If these guys are right...then we must have been having a major climate change...hint: global cooling...that they could not have survived. The earth is simply not a continuous perfect machine.
1 posted on 01/17/2003 11:09:44 PM PST by pepsionice
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2 posted on 01/17/2003 11:10:23 PM PST by Support Free Republic (Your support keeps Free Republic going strong!)
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To: pepsionice
The title does not accurately describe the article.
3 posted on 01/17/2003 11:17:27 PM PST by SpringheelJack
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To: pepsionice
An extraterrestrial object that impacted the Earth near the Yucatan in Mexico 65.51 million years ago doomed the dinosaurs and 70 percent of the Earth's other species...

Think of the extraterrestrial object as a "Cosmic SUV".

4 posted on 01/17/2003 11:26:05 PM PST by Mike Darancette
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To: SpringheelJack
They were already in the home stretch when K-T hit. It may have taken a another 30 million years...but they would have likely found themselves gone eventually, without the help of K-T.

Which brings on another delicate subject...was this cooling era a plus for mankind to develop?
5 posted on 01/17/2003 11:29:43 PM PST by pepsionice
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To: pepsionice
They were already in the home stretch when K-T hit. It may have taken a another 30 million years...but they would have likely found themselves gone eventually, without the help of K-T.

That's not what the article says.

"The K-T impact affected the Earth's living things severely and dramatically, but the climate changes right before the impact, by comparison, did not," says Wilf. "... The dinosaurs were well adapted to global warming and cooling, but not to giant speeding rocks from space."

6 posted on 01/17/2003 11:35:12 PM PST by SpringheelJack
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To: pepsionice
YEC read later
7 posted on 01/17/2003 11:37:08 PM PST by LiteKeeper
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To: RadioAstronomer; longshadow; PatrickHenry
Bolide bump!
8 posted on 01/17/2003 11:41:56 PM PST by Aracelis
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To: pepsionice
Which brings on another delicate subject...was this cooling era a plus for mankind to develop?

If you consider evolution to be the best theory to date. Otherwise, mammals would not have had the opportunity to diversify and fill the many eco-niches they do now.

9 posted on 01/17/2003 11:47:49 PM PST by Aracelis
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To: pepsionice
Wonder what the implications are of the poles switching polarity? Other than messing up compasses and dead reckoning.
10 posted on 01/18/2003 1:55:09 AM PST by Sam Cree
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To: Sam Cree
That's easy. We got the polka, keelbasa, and the population of Wisconsin!! How did I do?
11 posted on 01/18/2003 3:38:17 AM PST by Jimmy Valentine
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To: VadeRetro; jennyp; Junior; longshadow; *crevo_list; RadioAstronomer; Scully; Piltdown_Woman; ...
Dinosaurs!

[This ping list for the evolution -- not creationism -- side of evolution threads, and sometimes for other science topics. To be added (or dropped), let me know via freepmail.]

12 posted on 01/18/2003 3:59:55 AM PST by PatrickHenry (Creationists secretly admire PH)
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To: PatrickHenry
Thanks for the ping..I'll enjoy reading this at work later.
13 posted on 01/18/2003 4:25:16 AM PST by Focault's Pendulum (Boom Shakalaka Boom Shakalaka Boom Shakalaka)
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To: Piltdown_Woman
So cool! Looks like the KT impact theory has another set of data collaborating this event.

BTW, the title of the article is exactly backwards!

14 posted on 01/18/2003 4:45:24 AM PST by RadioAstronomer
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To: PatrickHenry
Thanks for the ping :-)
15 posted on 01/18/2003 4:51:27 AM PST by RadioAstronomer
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To: PatrickHenry
Buried in the article is a fairly detailed discussion on the dating methods used. Of course, to creos it's all magic anyway ...
16 posted on 01/18/2003 5:02:21 AM PST by Junior (Dating? I'm married!)
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To: Jimmy Valentine
"That's easy. We got the polka, keelbasa, and the population of Wisconsin!!"

Yeah, hahaha, you've definitely put your finger on it. That reminds me, I definitely like kielbasa and skywegian, thing maybe I'll makes some for dinner, will be good in all this cold weather...maybe the polarity is changing or something here in Miami.

17 posted on 01/18/2003 6:07:04 AM PST by Sam Cree
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To: pepsionice
The ones that survived gave rise to us.
18 posted on 01/18/2003 8:44:38 AM PST by stanz
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To: SpringheelJack
The title does not accurately describe the article.

No kidding. I had to read the whole thing to figure that out. Interesting how much warmer the globe was before the K-T impact.

19 posted on 01/18/2003 12:08:21 PM PST by RightWhale
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To: Sam Cree
>>>the implications are of the poles switching polarity<<

The RED wire would go to the "-" and the BLACK wire would go to the "+"

Like those 1960's VW bugs.
20 posted on 01/18/2003 12:11:00 PM PST by freedumb2003
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