Relationship found between ancient climate change and mass extinction

Feb 18, 2011 By Ellen Ferrante
This image shows coastal outcrop exposure of the Late Ordovician Ellis Bay Formation, Anticosti Island, Quebec, Canada. Credit: Seth Finnegan

(PhysOrg.com) -- 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 . The team found the occurred during a glacial period when 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 , 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 , the 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.

Explore further: Strong quake hits east Indonesia; no tsunami threat

add to favorites email to friend print save as pdf

Related Stories

An ancient Earth like ours

Aug 09, 2010

An international team of scientists including Mark Williams and Jan Zalasiewicz of the Geology Department of the University of Leicester, and led by Dr. Thijs Vandenbroucke, formerly of Leicester and now at ...

Seafloor Fossils Provide Clues on Climate Change

Oct 22, 2009

Deep under the sea, a fossil the size of a sand grain is nestled among a billion of its closest dead relatives. Known as foraminifera, these complex little shells of calcium carbonate can tell you the sea ...

Recommended for you

Strong quake hits east Indonesia; no tsunami threat

21 hours ago

A strong earthquake struck off the coast of eastern Indonesia on Sunday evening, but there were no immediate reports of injuries or damage, and authorities said there was no threat of a tsunami.

Scientists make strides in tsunami warning since 2004

Dec 19, 2014

The 2004 tsunami led to greater global cooperation and improved techniques for detecting waves that could reach faraway shores, even though scientists still cannot predict when an earthquake will strike.

Trade winds ventilate the tropical oceans

Dec 19, 2014

Long-term observations indicate that the oxygen minimum zones in the tropical oceans have expanded in recent decades. The reason is still unknown. Now scientists at the GEOMAR Helmholtz Centre for Ocean Research ...

User comments : 2

Adjust slider to filter visible comments by rank

Display comments: newest first

omatumr
2.6 / 5 (5) Feb 19, 2011
Earth's constantly changing climate has probably probably stimulated the evolution of different life forms:

1. "Earth's Heat Source - The Sun," Energy & Environment 20 (2009) 131-144.

arxiv.org/pdf/0905.0704

2. "Neutron repulsion", 19 pages, in press (2011)

arxiv.org/pdf/1102.1499v1

With kind regards,
Oliver K. Manuel
Former NASA Principal
Investigator for Apollo
rodgod
2.5 / 5 (2) Feb 19, 2011
It's been shown the Earth's magnetic poles 'flip' every so often. This can't be pretty. Minus the occasional (but inevitable) dinosaur-killing meteorite, the ( I want to say high-sulphur[?] content in) oceans between transitions have got to wreak havoc on fish/animal life. Can anyone dare to guess the length of the "flipping" process? Millenia, maybe even decades?

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.