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Evidence Of The 'Lost World': Did Dinosaurs Survive The Cretaceous Extinction?

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Reginese Dei
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« on: July 16, 2011, 02:12:37 am »

Evidence Of The 'Lost World': Did Dinosaurs Survive The End Cretaceous Extinctions?

ScienceDaily (Apr. 30, 2009) The Lost World, Sir Arthur Conan Doyle's account of an isolated community of dinosaurs that survived the catastrophic extinction event 65 million years ago, has no less appeal now than it did when it was written a century ago. Various Hollywood versions have tried to recreate the lost world of dinosaurs, but today the fiction seems just a little closer to reality.


New scientific evidence suggests that dinosaur bones from the Ojo Alamo Sandstone in the San Juan Basin, USA, date from after the extinction, and that dinosaurs may have survived in a remote area of what is now New Mexico and Colorado for up to half a million years. This controversial new research, published today in the journal Palaeontologia Electronica, is based on detailed chemical investigations of the dinosaur bones, and evidence for the age of the rocks in which they are found.

"The great difficulty with this hypothesis -- that these are the remains of dinosaurs that survived -- is ruling out the possibility that the bones date from before the extinction," says Jim Fassett, author of the research.

"After being killed and deposited in sands and muds, it is possible for bones to be exhumed by rivers and then incorporated into younger rocks" he explains. This is not the usual way in which fossil deposits of this kind form, but it has been shown to explain some other post-extinction dinosaur bones. Fassett has amassed a range of evidence that indicates that these fossils from the Ojo Alamo Sandstone were not exhumed and redeposited and that these dinosaurs really did live after the end Cretaceous extinction event.

The first step must be to demonstrate that the rocks containing the bones are younger than the extinction event. Fassett has analysed the magnetic polarity of the rocks, and the pollen grains they contain, different approaches to finding the age of rocks which, he concludes "independently indicate that they do indeed post-date the extinction".

Fassett also found that "the dinosaur bones from the Ojo Alamo Sandstone have distinctly different concentrations of rare earth metal elements to the bones in the underlying Cretaceous rocks" and this, he argues, "makes it very unlikely that the post-extinction bones were exhumed from the underlying sediments." This is supported by a find of 34 hadrosaur bones together -- "these are not literally an articulated skeleton, but the bones are doubtless from a single animal" -- if the bones had been exhumed by a river, they would have been scattered.

So does this provide conclusive proof that dinosaurs survived the Cretaceous extinctions? According to David Polly, one of the editors of the journal in which the research is published, "this is a controversial conclusion, and many palaeontologists will remain sceptical", but we already know that flying theropod dinosaurs (more generally referred to as birds) and crocodiles survived, so the possibility of pockets of survivors of other types of dinosaur is not quite as far fetched as it might sound.

Finding conclusive evidence, however, is a difficult matter when the crime scene is 65 million years old. "One thing is certain," continues Polly, "if dinosaurs did survive, they were not as widespread as they were before the end of the Cretaceous and did not persist for long." The 'Lost World scenario' of humans and dinosaurs existing at the same time, still belongs firmly in the realms of pure fantasy.
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    The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by The Palaeontological Association, via EurekAlert!, a service of AAAS.

Journal Reference:

   1. James Fassett. New Geochronologic and Stratigraphic Evidence Confirms the Paleocene Age of the Dinosaur-Bearing Ojo Alamo Sandstone and Animas Formation in The San Juan Basin, New Mexico and Colorado. Palaeontologia Electronica, April 29, 2009 [link]

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The Palaeontological Association (2009, April 30). Evidence Of The 'Lost World': Did Dinosaurs Survive The End Cretaceous Extinctions?. ScienceDaily. Retrieved July 16, 2011, from http://www.sciencedaily.com /releases/2009/04/090428092823.htm

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http://www.sciencedaily.com/releases/2009/04/090428092823.htm
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Reginese Dei
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« Reply #1 on: July 16, 2011, 02:13:48 am »



View eastward from divide between Ojo Alamo and Barrel Spring arroyos, Kirtland shale in foreground. Conical butte capped with lower part of Ojo Alamo sandstone. Butte at left consists of Kirtland shale at base, overlain by conglomeratic sandstone of Ojo Alamo, and that in turn by the middle or shale member of the same formation, with pebbles from the disintegrated upper conglomeratic member scattered over the top. San Juan County, New Mexico. Circa 1915. (Credit: Plate 71-A in U.S. Geological Survey / Bauer, C.M. 251)
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« Reply #2 on: July 16, 2011, 02:15:11 am »

Dinosaurs Survived Mass Extinction by 700,000 Years, Fossil Find Suggests[/b]

ScienceDaily (Jan. 28, 2011) University of Alberta researchers determined that a fossilized dinosaur bone found in New Mexico confounds the long established paradigm that the age of dinosaurs ended between 65.5 and 66 million years ago.


The U of A team, led by Larry Heaman from the Department of Earth and Atmospheric Sciences, determined the femur bone of a hadrosaur as being only 64.8 million years old. That means this particular plant eater was alive about 700,000 years after the mass extinction event many paleontologists believe wiped all non-avian dinosaurs off the face of earth, forever.

Heaman and colleagues used a new direct-dating method called U-Pb (uranium-lead) dating. A laser beam unseats minute particles of the fossil, which then undergo isotopic analysis. This new technique not only allows the age of fossil bone to be determined but potentially can distinguish the type of food a dinosaur eats. Living bone contains very low levels of uranium but during fossilization (typically less than 1000 years after death) bone is enriched in elements like uranium. The uranium atoms in bone decay spontaneously to lead over time and once fossilization is complete the uranium-lead clock starts ticking. The isotopic composition of lead determined in the hadrosaur's femur bone is therefore a measure of its absolute age.

Currently, paleontologists date dinosaur fossils using a technique called relative chronology. Where possible, a fossil's age is estimated relative to the known depositional age of a layer of sediment in which it was found or constrained by the known depositional ages of layers above and below the fossil-bearing horizon. However, obtaining accurate depositional ages for sedimentary rocks is very difficult and as a consequence the depositional age of most fossil horizons is poorly constrained. A potential weakness for the relative chronology approach is that over millions of years geologic and environmental forces may cause erosion of a fossil-bearing horizon and therefore a fossil can drift or migrate from its original layer in the strata. The researchers say their direct-dating method precludes the reworking process.

It's widely believed that a mass extinction of the dinosaurs happened between 65.5 and 66 million years ago. It's commonly believed debris from a giant meteorite impact blocked out the Sun, causing extreme climate conditions and killing vegetation worldwide.

Heaman and his research colleagues say there could be several reasons why the New Mexico hadrosaur came from a line of dinosaurs that survived the great mass extinction events of the late Cretaceous period (KT extinction event). Heaman says it's possible that in some areas the vegetation wasn't wiped out and a number of the hadrosaur species survived. The researchers also say the potential survival of dinosaur eggs during extreme climatic conditions needs to be explored.

Heaman and his colleagues believe if their new uranium-lead dating technique bears out on more fossil samples then the KT extinction paradigm and the end of the dinosaurs will have to be revised.

The research was published online, January 26, in the journal, Geology.
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    The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Alberta, via EurekAlert!, a service of AAAS.

Journal Reference:

   1. J. E. Fassett, L. M. Heaman, A. Simonetti. Direct U-Pb dating of Cretaceous and Paleocene dinosaur bones, San Juan Basin, New Mexico. Geology, 2011; 39 (2): 159 DOI: 10.1130/G31466.1

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University of Alberta (2011, January 28). Dinosaurs survived mass extinction by 700,000 years, fossil find suggests. ScienceDaily. Retrieved July 16, 2011, from http://www.sciencedaily.com /releases/2011/01/110127141707.htm


http://www.sciencedaily.com/releases/2011/01/110127141707.htm
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« Reply #3 on: July 16, 2011, 02:16:15 am »



U of A researcher Larry Heaman with the actual fossil that now throws into questions the KT paradigm. He is sitting in front the laser ablation machine. (Credit: Image courtesy of University of Alberta)
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« Reply #4 on: July 16, 2011, 02:17:55 am »

New Blow Against Dinosaur-Killing Asteroid Theory, Geologists Find

ScienceDaily (Apr. 28, 2009) — The enduringly popular theory that the Chicxulub crater holds the clue to the demise of the dinosaurs, along with some 65 percent of all species 65 million years ago, is challenged in a paper to be published in the Journal of the Geological Society on April 27, 2009.


The crater, discovered in 1978 in northern Yucutan and measuring about 180 kilometers (112 miles) in diameter, records a massive extra-terrestrial impact.

When spherules from the impact were found just below the Cretaceous-Tertiary (K-T) boundary, it was quickly identified as the "smoking gun" responsible for the mass extinction event that took place 65 million years ago.

It was this event which saw the demise of dinosaurs, along with countless other plant and animal species.

However, a number of scientists have since disagreed with this interpretation.

The newest research, led by Gerta Keller of Princeton University in New Jersey, and Thierry Adatte of the University of Lausanne, Switzerland, uses evidence from Mexico to suggest that the Chicxulub impact predates the K-T boundary by as much as 300,000 years.

"Keller and colleagues continue to amass detailed stratigraphic information supporting new thinking about the Chicxulub impact, and the mass extinction at the end of the Cretaceous," says H. Richard Lane, program director in the National Science Foundation (NSF)'s Division of Earth Sciences, which funded the research. "The two may not be linked after all."

From El Penon and other localities in Mexico, says Keller, "we know that between four and nine meters of sediments were deposited at about two to three centimeters per thousand years after the impact. The mass extinction level can be seen in the sediments above this interval."

Advocates of the Chicxulub impact theory suggest that the impact crater and the mass extinction event only appear far apart in the sedimentary record because of earthquake or tsunami disturbance that resulted from the impact of the asteroid.

"The problem with the tsunami interpretation," says Keller, "is that this sandstone complex was not deposited over hours or days by a tsunami. Deposition occurred over a very long time period."

The study found that the sediments separating the two events were characteristic of normal sedimentation, with burrows formed by creatures colonizing the ocean floor, erosion and transportation of sediments, and no evidence of structural disturbance.

The scientists also found evidence that the Chicxulub impact didn't have the dramatic impact on species diversity that has been suggested.

At one site at El Penon, the researchers found 52 species present in sediments below the impact spherule layer, and counted all 52 still present in layers above the spherules.

"We found that not a single species went extinct as a result of the Chicxulub impact," says Keller.

This conclusion should not come as too great a surprise, she says. None of the other great mass extinctions are associated with an impact, and no other large craters are known to have caused a significant extinction event.

Keller suggests that the massive volcanic eruptions at the Deccan Traps in India may be responsible for the extinction, releasing huge amounts of dust and gases that could have blocked out sunlight and brought about a significant greenhouse effect.
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http://www.sciencedaily.com/releases/2009/04/090427010803.htm
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« Reply #5 on: July 16, 2011, 02:19:28 am »



This artist's rendering shows the Chicxulub crater at the time of the meteorite's impact. (Credit: NASA)
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