Early Earth Had Periodic Organic Haze

From the article:

Zerkle's team analyzed the geochemistry of marine sediments deposited between 2.65 and 2.5 billion years ago in what is now South Africa.

They found evidence of local production of oxygen by microbes in the oceans, but carbon and sulphur isotopes indicate that little of that oxygen entered the atmosphere.

Instead, the authors suggest, the atmosphere transitioned repeatedly between two states: one with a thin, hydrocarbon haze and the other haze-free.

Interesting, but it seems like a huge conclusion based on a very small sample of data. If the area they sampled was (say) 10 square miles, that's only 3.7x10^-9 % of the Earths' surface.

I'm not a geologist, but I think South Africa is one of the very few places where rocks that old are easy to get at. And the (somewhat vague) article says the findings jibe with NASA's early climate modeling.

Of course it's possible something peculiar was happening just above that region of (then) ocean floor. So perhaps someone will follow up with additional studies elsewhere.