Will we ever know for sure what all happened to the dinosaurs?
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Dino 'survival' claim disputed
By Paul Rincon
BBC News Online science staff
The idea that dinosaurs survived for some time after the asteroid impact
for wiping them out 65 million years ago has been dealt a blow. Dinosaur
egg fragments dug out of rocks in China seem to postdate the dramatic
extinction event popularly believed to have extinguished the creatures.
But new data suggests the egg pieces got mixed up in later deposits
action of mud and debris flows.
Details of the latest findings are published in the Journal of Geology.
Dinosaurs survived until the end of the Cretaceous Period of Earth
by the beginning of the Tertiary Period, about 65 million years ago, they
At numerous sites around the world, a clay layer separates rocks laid
down in the Cretaceous from those deposited in the Tertiary. This is
known as the K-T boundary.
The boundary contains high concentrations of the element iridium,
in meteorites. Researchers have proposed that a meteorite impact which
a huge crater at Chicxulub in Mexico, could have been responsible for the
of the creatures.
Discoveries of dinosaur egg fragments in deposits from Nanxiong Basin,
China, which contain Tertiary animal remains and pollen, suggested
there could have survived until about 62 million years ago.
But US and Chinese researchers now dispute this. They claim the egg
pieces originated in Cretaceous deposits and were swept up in mud and
debris flows during the Tertiary. This jumbled material was then
Dr Brenda Buck of the University of Nevada, Las Vegas, US, said she came
upon the idea while examining palaeosols, ancient soils that have been
buried and later exposed in Nanxiong.
"During the dry season you had these big open cracks," she explains.
"Mudflows would come down and fill in those cracks. All those mudflows
are in the [rock] sections where the flora and fauna are mixed."
Dr Buck suggests the presence of several iridium layers at Nanxiong
supports a view that Cretaceous rocks were reworked in the Tertiary.
There have been other claims for the survival of dinosaurs into Tertiary
times at sites in Montana and New Mexico in the US, in Bolivia and in
All of these claims have been questioned by other researchers.
"The only really well documented dinosaur remains are from the American
actually have no idea what's happening anywhere else in the world," Dr
Norman MacLeod, keeper of palaeontology at the Natural History Museum in
London, told BBC News Online.
"We know that they lived on other continents, so there's no particular
reason to suppose that that western US population was the last
"It could well be that they went above the K-T boundary in other parts of
the world, especially parts that were remote from the Chicxulub impact."
Story from BBC NEWS:
STEPHAN PICKERING / Chofetz Chayim ben-Avraham
The Dinosaur Fractals Project
2333 Portola Drive # 4
Santa Cruz, California 95062-4250 USA
theropod research summarized: <www.dinodata.net>
see under PICKERING at their Reference Base
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