Fossil Evidence of Extreme Warmth in the Cretaceous Arctic
In the December 18 issue of Science, John Tarduno and his
collaborators published some of their findings from the Paleomagnetic
Research Group's Arctic Expeditions. In 1996, the expedition team
literally stumbled across a unique fossil find: vertebrate remains from
fish, turtles and champsosaurs. The find is unique in that
champsosaurs, a semi-aquatic reptile resembling crocodiles, had not
been found that far north. Geographic reconstructions, based on global
paleomagnetic data sets, places the fossil site above the Arctic circle
86 to 95 million years ago.
Evidence for Extreme Climatic Warmth from Late
Cretaceous Arctic Vertebrates
J. A. Tarduno*, D. B. Brinkman, P. R. Renne, R. D. Cottrell, H. Scher,
P. Castillo
Abstract
A Late Cretaceous (92 to 86 million years ago) vertebrate assemblage from the
high Canadian Arctic (Axel Heiberg Island) implies that polar climates were
warm (mean annual temperature exceeding 14°C) rather than near freezing. The
assemblage includes large (2.4 meters long) champsosaurs, which are extinct
crocodilelike reptiles. Magmatism at six large igneous provinces at this time
suggests that volcanic carbon dioxide emissions helped cause the global warmth.
J. A. Tarduno, R. D. Cottrell, H. Scher, Department of Earth and Environmental Sciences, University of Rochester,
Rochester, NY, 14627, USA. D. B. Brinkman, Royal Tyrrell Museum of Palaeontology, Drumheller, Alberta, TOJ OYO,
Canada. P. R. Renne, Berkeley Geochronology Center, Berkeley, CA 94709, USA. P. Castillo, Geological Research Division,
Scripps Institution of Oceanography, La Jolla, CA 92093-0220, USA
*To whom correspondence should be addressed.
E-mail:john@earth.rochester.edu
Also in Science
Enhanced Perspectives: Summary
Tropical Paradise at the Cretaceous Poles?
Brian T. Huber
A growing body of evidence indicates that the polar regions were at one time much warmer than they are now. In his
Perspective, Huber discusses a report in the same issue by Tarduno et al. that describes the fossil remains of a
crocodile-like creature discovered in the high Canadian Arctic zone at Axel Heiberg Island. This, together with other
elements of the paleobiological record, provides further evidence of polar warmth during the Cretaceous. The source of the
warming appears to be high concentrations of carbon dioxide during this period, although further modeling and physical
evidence will be needed to conclusively sort out the causes.
Read a little about the find in the latest edition of
Currents
Here are some of the text versions of articles that have appeared in
newspapers concerning the Science article as well as links to
other sites and articles:
Times of London
December 18, 1998
Ancient crocs roamed a balmy Arctic
BY NIGEL HAWKES
SCIENCE EDITOR
NINETY million years ago crocodile-like creatures
wandered an Arctic that was as warm as Florida is today,
an American team has discovered.
Remains of an 8ft-long champsosaur, which had a long
snout and razor-sharp teeth, show that, for about six
million years, the Arctic was balmy. The bones were
found by an expedition led by Professor John Tarduno, of
the University of Rochester, to Axel Heiberg Island in the
Canadian Arctic. To breed, the reptiles needed an
extended warm period each summer with temperatures
rising to the 80s and 90s.
Professor Tarduno believes that those temperatures were
provided by vast amounts of carbon dioxide released by
volcanoes. The fossils were found in sedimentary rocks on
top of a deep layer of volcanic basalts, he and colleagues
reported in Science.
Earlier finds of fossil trees 1,000 miles from any tree living
today had shown the Arctic was once much warmer than
today, but there had been no evidence that it was warm
enough to support such reptiles.
Champsosaurs, or "crocodile lizards", lived in freshwater
streams in Europe and North America throughout the
Cretaceous Period (from 144 to 65 million years ago) and
were one of the few reptiles to survive the mass extinction
of dinosaurs at the end of the Cretaceous.
They preyed on fish or small dinosaurs and were good
swimmers, with a low centre of gravity that made them
especially agile in the water.
BBC News
Friday, December 18, 1998 Published at 13:38 GMT
Sci/Tech
Some like it hot
How could this creature live so far north?
The remains of a crocodile-like beast dug up in the
Arctic circle suggest the Earth may have experienced a
period of intense global warming some 90 million years
ago.
The bones, which belonged to a creature called a
champsosaur, were unearthed at Axel Heiberg Island in
northern Canada.
The fossils of fish and turtles were also discovered with
the reptile.
What we know of
champsosaurs and modern
crocodiles, says the team
that found the animal, in
particular their size, lifestyle
and breeding behaviour,
means temperatures in the
Arctic during the late
Cretaceous period must have
been much higher than today
to allow them to live so far
north.
The researchers from the
University of Rochester, New York, estimate that the
annual mean temperature in that part of the world was
greater than 14C ( 57F).
This implies it was rarely, if ever, freezing during the
winter, and summer temperatures would have
consistently reached into the late 20s and early 30s
Celsius (80s and 90s Fahrenheit). In other words, the
climate in this part of the Arctic would have been similar
to modern-day Florida.
Global warming
The evidence from fossilised plants has encouraged
scientists to think that the late Cretaceous was a warm
time - but not this warm. The Rochester team says
global warming would be one explanation.
The fossils were found in a
layer of sediment right on top
of 300 metres (1,000 ft) of
hardened lava, known as
basalt. Geologists know that
right across the globe this
basalt was pumped onto the
surface of the Earth in vast
quantities and over
thousands of years.
These floods of boiling rock
would have released many
millions of tonnes of gas into
the atmosphere including huge amounts of carbon
dioxide - the main gas though to drive the greenhouse
effect.
"We can't avoid the fact that these fossils are sitting
right on top of this extremely large volcanic eruption,"
says Professor John Tarduno who led the expedition that
found the champsosaur bones.
"And if you look around the world, it was an unusually
active time, with many eruptions occurring at the same
time. It's very reasonable to suggest that so much CO2
was dumped into the atmosphere that it overwhelmed
the system, causing global warming."
Climate puzzle
The scenario painted by Rochester will need further
explanation because it is not easy to have such warm
polar temperatures without also having unrealistically
high equatorial temperatures.
"This will be a puzzle for
people who model climate,"
says Tarduno, "but the
fossils, together with the
radiometric dating, provide
very hard evidence of
extremely warm
temperatures in the Arctic."
The team found a variety of
champsosaur bones from jaw
bones and abdominal ribs to
hip bones and backbones.
The creature would have lived
a semi-aquatic existence and would have been about 2.4
metres long (8 ft).
The champsosaur find is reported in the journal Science.
The champsosaur painting is by Jerome Connolly;
courtesy of the Science Museum of Minnesota
ABC News
SCIENCE HEADLINES
Reptiles Enjoyed Warm Arctic
Discovery Channel On-Line
Prehistoric reptiles in the balmy Canadian Arctic
This page was last updated January 11, 1999
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