The rare find, dating from 2.9 billion years ago, was made in South Africa.
“We looked at relative amounts of 3 oxygen isotopes, 16O, 17O, and 18O. These are all types of oxygen but have very slightly different weights. We found that these rocks had very low amounts of 18O, and very high amounts of 17O, indicating that they were formed at icy temperatures. This means ice. Couple that geochemical evidence with the moraine evidence, and it means glaciers, the oldest glaciers yet found on Earth”.
“It may be that this area was close to the poles. Another possibility is that the whole Earth was in a 'snowball Earth' period, when low atmospheric concentrations of CO2 and CH4 led to a ‘reverse greenhouse effect,’ causing much of the planet to freeze. Scientists believe that this may have happened on a couple of occasions in the more recent past. If so, this would be the earliest such global cooling period recorded. Either possibility is scientifically interesting,” said Hofmann.
“The largest sedimentary gold deposits in the world are found in slightly younger rocks sitting above the rocks we studied. It’s possible that a change from icehouse to greenhouse conditions may have aided in the formation of those gold deposits, but this needs to be confirmed and requires further work”.
Dr. Andrey Bekker, associate professor at the Department of Earth & Planetary Sciences, University of California, Riverside, further said“Evidence for glaciation of this age has been hotly discussed and debated for decades based on sedimentological evidence with suggestions ranging from high altitude to high latitude glaciation. Triple oxygen isotope analysis add an entirely new line of evidence to this argument.
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