New Oxygen research; from rocks, higher earlier (Introduction)

by dhw, Saturday, August 27, 2016, 07:39 (2801 days ago) @ David Turell

QUOTE: The team's study identifies, for the first time, exactly how much oxygen was in Earth's atmosphere 813 million years ago -- 10.9 percent. This finding, they say, demonstrates that oxygenation on Earth occurred 300 million years earlier than previously concluded from indirect measurements.
"'Diversity of life emerges right around this time period," Benison said. (dhw's bold)-No it doesn't. It emerges 300 million years later.-QUOTE: "We used to think that to have diversity of life we needed specific things, including a certain amount of oxygen. (The findings) show that not as much oxygen is required for organisms to develop." -No they don't. We need to know the amount of oxygen during the Cambrian, and the article does not even mention that!
 
David: It is my impression that this new early oxygen level discovery removes most of the previously presumed oxygen rise in the immediate pre-Cambrian period. Thus the question arises as to why the Cambrian diversity explosion waited so long!

I don't know where you get that impression from, since the article does NOT tell us the amount of oxygen during the Cambrian! Here are two more articles:-	The Cambrian Period - UCMP
www.ucmp.berkeley.edu/cambrian/cambrian.php
21/08/2016 • The Cambrian Period. ... the oceans became oxygenated. Although there was plentiful atmospheric oxygen by the beginning of the period, ...-QUOTE: "Also during the Cambrian, the oceans became oxygenated. Although there was plentiful atmospheric oxygen by the beginning of the period, it wasn't until the Cambrian that there was a sufficient reduction in the number of oxygen-depleting bacteria to permit higher oxygen levels in the waters. (My bold) This dissolved oxygen may have triggered the "Cambrian Explosion" — when most of the major groups of animals, especially those with hard shells, first appeared in the fossil record.-And the following refers to research done in 2014:-When life exploded | Science News for Students
https://www.sciencenewsforstudents.org/article/when-life-exploded-QUOTE: "Spear's team found sulphate levels 830 million years ago were just 10 percent as high as they are today. […] by the end of the Precambrian, about 540 million years ago, ocean sulphate levels had risen to between 50 percent and 80 percent of today's levels. Oxygen levels would have risen by a similar amount, says Spear at Penn State.
Another recent study [Yale University] also showed that low oxygen levels played a role in delaying the great diversification of life. Together, these studies provide snapshots of how much richer in oxygen the world's oceans grew in the buildup to the Cambrian Explosion over hundreds of millions of years."-The 10 percent 830 million years ago is only just below the 10.9 percent mentioned in your article, which does not tell us the level leading up to the Cambrian. This article tells us it rose to 50-80%. I wasn't around at the time, but I'm certainly not going to conclude that your article “removes from consideration that the Cambrian explosion almost 300 million years later was triggered by oxygen.”