What do Proterozoic-aged red beds and banded iron formations tell us about the Earth's early atmosphere?
Banded iron formations indicate that there were oxygen-rich and oxygen-poor episodes during Earth's early atmosphere. Banded iron formations first appear in the Archean, 3 bil…lion years ago. Unbanded iron deposits (red beds) from the Proterozoic, 1.8 billion years ago, indicate that the atmosphere became oxygen rich and that oxygen-poor episodes were no longer prevalent. (MORE)