Kimberley rocks tell first mass extinction of complex life

May 30, 2014 by Kerry Faulkner
Basalt rocks formed from cooled lava, in Marella Gorge, north-east Kimberley. Credit: Lena Evins

Volcanic eruptions across a vast area of what is now Western Australian and the Northern Territory 510 million years ago caused the first known mass extinction of complex life forms.

Curtin University's Dr Fred Jourdan says it is widely documented that the Early-Middle Cambrian extinction of complex multicellular life was related to changes in and depletion of oxygen in the oceans but the exact cause has been unknown until now.

He is part of an international team of scientists that calculated a near perfect chronological correlation between large volcanic eruptions, climate changes and over the history of life during the last 550 million years.

The eruptions produced rapid fluctuations in climate making it difficult for species to survive.

The research team's findings High-precision dating of the Kalkarindji large igneous province, Australia, and synchrony with the early–Middle Cambrian (Stage 4–5) extinction, have been reported in the journal Geology.

The paper concludes the likely factors responsible for the Early–Middle Cambrian extinction are rapid climate shifts triggered by emitting mantle gases and greenhouse gases methane and carbon dioxide, either dissolved in the magma or generated by the interaction between magma and evaporite layers and/or oil-rich rocks.

Primative ocean life

Since there was no existing fauna or flora on land during the period, the mechanism must have acted on the oceans.

Life at that time would have included the reef building sponge-like organism Archaeocyathids and Trilobites, the most primitive groups.

Dating techniques

The team used high-precision 40Ar/39Ar and U-Pb mineral dating to measure the age of eruptions in the Kalkarindji volcanic province in the Northern Territory and Western Australia where lavas covered more than two million square kilometres.

Both techniques are based on completely different elements and give the same age for the lavas, which is a strong validation that the age is correct.

Insights into gas emission effect

Dr Jourdan says the research is vital to understanding the long term implications that modern-day massive gas emission into the atmosphere can have on the climate and life.

"I'm talking about greenhouses gases like methane and which warm the climate and sulphur dioxide which can cool the climate for short periods of time but more relevant to now, can cause acid rains which can wreck ecosystem and massive toxic pollution; part of the irritant pollutants in Beijing come from sulphur dioxide.

"…we can see the effect of those gases on nature by studying the rock record, and we are injecting a massive amount of those into the atmosphere, mostly by burning fossil fuels like coal and oil."

Explore further: End-Permian extinction happened in 60,000 years—much faster than earlier estimates, study says

More information: F. Jourdan, K. Hodges, B. Sell, U. Schaltegger, M.T.D. Wingate, L.Z. Evins, U. Söderlund, P.W. Haines, D. Phillips, and T. Blenkinsop. "High-precision dating of the Kalkarindji large igneous province, Australia, and synchrony with the Early–Middle Cambrian (Stage 4–5) extinction." Geology, G35434.1, first published on April 24, 2014, DOI: 10.1130/G35434.1

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Maggnus
4.6 / 5 (11) May 30, 2014
This is another example of CO2 (and other GHG) driving climate change.

I like to keep pointing these out, as there are instances of both effects; that is, climate change driving a rise in CO2 levels, and rising CO2 levels driving a change in climate. A certain denialist keeps insisting it only works one way.
Jimee
5 / 5 (7) May 30, 2014
97 to 3 informed scientists find enough evidence to support the theory that human activities are responsible for rising levels of CO2 and thus global warming and extreme climate change. Enough with the fanatical, radical denial and time to begin a dialogue about responsible actions to mitigate the effect on our children, and their children.
Torbjorn_Larsson_OM
5 / 5 (3) May 31, 2014
Too bad that the West Antarctic ice sheet is now observed be going, with nothing known to be stopping it, a process now believed to have been started independent of manmade CO2 some 5000 years ago but certainly pushed into fantastic rates by us.

That means that CO2 mitigation will control the rate of ocean increase up to the WA 6 m contribution, but that the 6 m will happen whatever we do. If we hadn't put out the CO2 maybe, just maybe, the next ice age would have happened and the increase would have reversed eventually.

So, 2 important things on the agenda:

1. Start to control the CO2 and manage the best economy between its change rate (since managing CO2 gives a net economical benefit, we know this since the -97 Stevens report) and the environment (including sea level rise) change rate.

2. Start to plan for our grandchildren's coast lines. New York is a goner, but some may squeeze through. (Say, north Sweden has still net land raise due to the ice age remnant stress release.)
Torbjorn_Larsson_OM
5 / 5 (2) May 31, 2014
Speaking of that most known coastal cities will be cheap submarine property a few generations hence, think of the Netherlands and parts of Oceania...

Eventually some can put down cities on west Antarctica, naturally. IIRC the inner part will be an inland sea, ~1 km below the ocean surface, but the rand may be a cold, desolate area that will be marginally habitable.