[D66] Relationship Found Between Ancient Climate Change and Mass Extinction

[Henk Elegeert]

*Relationship Found Between Ancient Climate Change and Mass
Extinction*<http://www.nsf.gov/discoveries/disc_summ.jsp?cntn_id=118671&WT.mc_id=USNSF_1>

*Researchers use a ground-breaking technique that reveals a relationship
between cooler temperatures and Earth's second largest mass extinction,
which occurred about 450 million years ago*
  [image: Photo of a coastal outcrop exposure of Late Ordovician Ellis Bay
Formation.]

Coastal outcrop exposure of Late Ordovician Ellis Bay Formation, Anticosti
Island, Quebec, Canada.
Credit and Larger
Version<http://www.nsf.gov/discoveries/disc_images.jsp?cntn_id=118671&org=NSF>

*February 17, 2011*

In the Late Ordovician Period of Earth's geologic history, about 450 million
years ago, more than 75 percent of marine species perished and Earth
scientists have been seeking to discover what caused the extinction. It was
the second largest in Earth's history.

Now, using a new research method, investigators believe they are closer to
finding an answer.

Employing a new way to measure ancient ocean temperatures, a team of
researchers at the California Institute of Technology (Caltech) recently
discovered a link between ancient climate change and the Late Ordovician
mass extinction. The team found the extinction event occurred during a
glacial period when global temperatures became cooler and the volume of
glacial ice increased.

Both the changes in temperature and the increase of continental ice sheets
are factors that could have affected marine life in these ancient waters,
said Woodward Fischer, an assistant professor of geobiology at Caltech.

"Our tools are getting better to ask more questions about ancient climate,
so we're really shaping our picture of what that world was like," he said.

In the past, measuring ancient ocean temperatures was based on measuring the
ratios of oxygen isotopes found in minerals from ocean water. The challenge
was knowing the concentration of isotopes in the ocean at that time, which
was needed to determine past water temperatures. But, because there is no
direct record of the isotopic composition of ancient oceans, it was
difficult to determine the water temperature.

The new method, developed in the laboratory of John Eiler, Sharp Professor
of Geology and professor of geochemistry at Caltech, determines the
temperature of the ocean by examining the spatial organization of isotopes
in fossils that existed in the Late Ordovician Period; in particular, the
method looks at the extent to which rare isotopes group together into the
same chemical unit in a mineral structure.

This new method "requires really well-preserved minerals, so we used
fossils," explained Fischer. "Shells are ideal for this technique."

Fossilized marine species shells were used from present-day Quebec, Canada,
and from the mid-western United States.

Fischer said the types of species that went extinct during the Late
Ordovician Period included mostly benthic invertebrates, or invertebrates
that live on the ocean floor and filter plankton for food. These were
organisms such as trilobites and brachiopods. Paleozoic corals and
cephalopods, which Fisher described as resembling "squids in a tube," were
impacted as well. Some vertebrates, primarily fish, also were impacted by
the change in global temperature, but fossil evidence of these organisms is
less common.

Eiler explained that the findings of this study revealed that during the
Late Ordovician, the temperatures of tropical oceans were higher than they
are today, but for a brief period, experienced a drop in temperature by five
degrees. At the same time, the volume of ice in the poles expanded. After
this glacial period, the ocean temperatures rose, and the ice volume
returned to its earlier, lower amount.

"We've observed a cycle of climate variability," said Eiler, who explained
that these findings can be used to learn more about changes in climate
today.
  --  Ellen Ferrante, (703) 292-2204 emferran at nsf.gov

*Investigators
*John Eiler

*Related Institutions/Organizations
*California Institute of Technology

*Related Awards
*#0643394 Collaborative Research: Testing Hypotheses of Global Warming
during Three Major Mass Extinctions
<http://www.nsf.gov/awardsearch/showAward.do?AwardNumber=0643394>

*Total Grants
*$242,107

"

 ... en wij ons maar druk maken over global warming.

Henk Elegeert
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