Study shows planet’s atmospheric oxygen rose through glaciers, climate swung so extremely that the polar ice caps extended to the equator and the Earth was a snowball
From the UNIVERSITY OF WYOMING
A University of Wyoming researcher contributed to a paper that determined a “Snowball Earth” event actually took place 100 million years earlier than previously projected, and a rise in the planet’s oxidation resulted from a number of different continents — including what is now Wyoming — that were once connected.
“Isotopic dating of the Ongeluk large igneous province, South Africa, revealed that the first Paleoproterozoic global glaciation and the first significant step change in atmospheric oxygenation likely occurred between 2,460 and 2,426 million years ago, approximately 100 million years earlier than previous estimates,” says Kevin Chamberlain, a UW research professor in the Department of Geology and Geophysics. “And the rise of atmospheric oxygen was not monotonic but, instead, was characterized by significant oscillations before irreversible oxygenation of the atmosphere 2,250 million years ago.”
Chamberlain is the second author of a paper, titled “Timing and Tempo of the Great Oxidation Event,” which appears in the Feb. 6 (today’s) issue of the Proceedings of the National Academy of Sciences (PNAS). The journal is one of the world’s most prestigious multidisciplinary scientific serials, with coverage spanning the biological, physical and social sciences.
Ashley Gumsley, a doctoral student at Lund University in Lund, Sweden, is the paper’s lead author. Other contributors were from the Geological Survey of Canada in Ottawa; Swedish Museum of Natural History; University of Johannesburg, South Africa; and the University of California-Riverside.
The research relates to a period in Earth’s history about 2.45 billion years ago, when climate swung so extremely that the polar ice caps extended to the equator and the Earth was a snowball, and the atmosphere was largely isolated from the hydrosphere, Chamberlain says. Recovery from this Snowball Earth led to the first and largest, rapid rise in oxygen content in the atmosphere, known as the Great Oxygenation Event (GOE), setting the stage for the dominance of aerobic life, he says.
A later, and better known, Snowball Earth period occurred at about 700 million years ago, and led to multicellular life in the Cambrian period, Chamberlain says. The events show there was not one event, but an oscillation of oxygen over time that led to the Earth’s conditions today.
“So, both Snowball Earth periods had extreme impacts on the development of life,” he says. “It helps us understand the evolution of Earth and Earth’s atmosphere, and evolution of life, for that matter.”
Chamberlain’s contribution focuses on igneous rocks exposed in South Africa that record the existence of equatorial glaciers and contain chemical indicators for the rise of atmospheric oxygen. Chamberlain’s in situ method to determine the age of the rocks does not require removing baddeleyite crystals from the rock. This process allows for analysis of key samples with smaller crystals than previously allowed. Using a mass spectrometer, the age of the rocks is determined by measuring the buildup of lead from the radioactive decay of uranium, he says.
“The basic story had been worked out earlier by others, but our results have significantly refined the timing and duration of the ‘event,’ which is more of a transition actually,” Chamberlain explains. “With all the discussion of climate change in the present day, understanding how Earth responded and the effects on the atmosphere in the past may help us predict the future.”
Chamberlain points to a Wyoming connection in this research. From paleomagnetic data, many of the continents, at the time, including the basement rocks of Wyoming, were all connected into a single, large continent and situated near the equator. Other continents connected included parts of what are now Canada and South Africa. This situation is part of the trigger for the “Snowball Earth” conditions.
“There are glacial deposits exposed in the Medicine Bow Mountains and Sierra Madre that are from this same event,” he says.
These rocks, known as diamictites, have large drop stones that depress very fine-grained mudstone. The large stones dropped from the underside of glacial sheets as they spread out and melted over shallow seas, similar to sediments beneath the Ross sea ice sheet of Antarctica today.
“The fact that these sediments were at the equator at 2.45 billion years ago comes from the paleomagnetic data from associated igneous rocks,” Chamberlain says.
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Hmm. I thought that ocean photosynthesis had been producing O2 for a long time, hundreds of millions of yrs or more, oxidizing dissolved iron in the ocean (the huge iron oxide deposits everywhere), before the iron was finally used up and starting accumulating in the atmosphere.
That’s my understanding . That the O2 came from a > 20% CO2 , 0% O2 atmosphere by biological sequestration as coal , gas , and limestone .
How a “snowball” period would do anything other than retard that conversion I fail to understand .
Ever since my first years studying geology I have been fascinated with globally extensive glaciation. So, it’s no surprise the first book I wrote taps on this idea. (published this week! Shameless plug for Icefall! Yay!) The causes I used in my story for global glaciation ending modern humanity along with most of the life on Earth are about as scientific as explaining how fast zombies came to be, but that doesn’t make me any less fascinated for the scientific study of actual *global* glaciation.
Great reading the comments in the thread, as well as ptolemy2’s pdf link.
There is some observational data that indicates the subject did happen. Arguing climatic reasons why it could or could not have happened makes no sense given the different conditions 2.5 billion years ago ie, earth orbit, obliquity, precession, solar tsi production, atmospheric density and composition, ocean depths and composition, lunar orbit and influences, etc., just to name a few. An interesting subject, none the less, when one then begins to consider future ramifications beyond that 2.5 bya.
This paper alleges just the opposite- oxygenic photosynthesis led to snowball earth.
http://authors.library.caltech.edu/1015/1/KOPpnas05.pdf
It could very well have contributed. Oxygen in the atmosphere means also ozone, that alters the temperature gradient of the atmosphere, warming the stratosphere and cooling the troposphere.
I had the pleasure of working for Dr. Chamberlain. I spent many hours at the microscope picking zircons much smaller than the tip of a human hair. The zircons were chosen for size, double termination,a lack of cracks and other defects. After enough zircons were pulled from a sample they were abraded down to a core to remove any part that might have been contaminated by other uranium/lead sources. The zircons were then dissolved in nitric acid and run through a mass spectrometer to obtain ratios of daughter products which were compared to half life ratios to determine the age of the samples. It took several 5 gallon buckets of rock to produce a couple of tiny samples, if we were lucky. Dr. Chamberlain and the students that work for him do some meticulous work.
Not that I expect, or even want, an answer – but just how does one go about picking a microscopic zircon crystal from a rock?
Sorry about taking so long to reply. Rock is crushed in a ball mill using steel balls or chains to break down the rock to fine particles. Some small Zircon crystals with a hardness of about 7.5 manage to stay intact through the process of milling and separation. Under a microscope they looked like a king’s ransom in jewels.
Science? Or fantasy? You decide ; )
Science. Obviously.
Observations of nature. Not flights of fancy.
So, if any “observations of nature” are involved, it’s science to you? . . Sad.
Yes, John, sorry but observations of nature are how science is done. Your cult however is based upon made-up stories. That’s myth, not science.
Where the man-made-up supposed Word of God differs from the actual Work of God, you have to go with the observations. That is, unless your god is unspeakably evil, sadistic, incompetent and deceptive.
Was that comment also science, Gloateus? ; )
My favorite part;
“With all the discussion of climate change in the present day, understanding how Earth responded and the effects on the atmosphere in the past may help us predict the future.”
Yes. It describes the unavoidable conclusion of attempting to believe literally in biblical passages when comparing them with objective reality.
JohnKnight
February 8, 2017 at 1:05 pm
That obeisance to the prevailing paradigm is not the heart of the paper.
Diamictite drop stones at low latitudes are observations scientific evidence. Your biblical myths are fantasies. Not being able to grasp the difference and confusing fact with fantasy could be considered a mental health issue, were it not a religious cult.
The snow-line in the tropics is about 5km high. So even today if an equatorial continent was big enough and high enough an ice sheet could easily form at the equator but would still leave the surrounding warm sea free to provide the moisture for snow.
Question to the geologists on this thread:
Is any evidence available for a massive magmatic event in the oceans around the peak temperatures in this graph?
The latest warm period can be linked to the Ontong Java event.
Given the maximum age of the current oceanic crust I’m afraid older events can not be traced anymore, but who knows.
What I’m interested in, and doesn’t seem to be addressed, is by what mechanism or theorized mechanism was oxygen generation caused by snowball Earth events? They certainly seem to be implying it was a causative factor.
During a low-latitude ice-age large amounts of hydrogen peroxide produced by UV light gets incorporated into the ice. When the temperature rises and the ice melts the hydrogen peroxide breaks down into water and oxygen. There is actually some H2O2 in Antarctic snow today, but not enough to matter because there is not enough UV light at high latitudes.
On actually reading the paper I see that he ascribes the oxygenation to increased photosynthetic activity causing drawdown of methane and carbon dioxide and hence glaciation. However this is probably just a genuflection to the almighty power of greenhouse gases, since elsewhere in the paper it is clearly shown that “the great oxygenation evant” actually happened just after the glaciation, so I tend to believe in the proxide mechanism instead, particularly since the (relatively) high-oxygen stage seems to have been short. Cyanobacteria would presumably have gone on producing oxygen.
“These rocks, known as diamictites, have large drop stones that depress very fine-grained mudstone. The large stones dropped from the underside of glacial sheets as they spread out and melted over shallow seas, similar to sediments beneath the Ross sea ice sheet of Antarctica today.”
I wonder how he determined that they were from the underside of a shelf-ice rather than from melting icebergs (which is usually the case)