It has long been suspected that the real culprit in keeping Earth’s atmosphere low oxygen was iron.
http://paleobiology.si.edu/geotime/main/htmlversion/proterozoic4.html
“In the absence of free oxygen, iron dissolves in water. This resulted in ocean waters that contained a great deal of dissolved iron. The dissolved iron bonded with oxygen released into ocean water by photosynthesizing cyanobacteria to form magnetite (Fe3O4). This magnetite was then deposited on the ocean floor.
“A vast amount of iron dissolved in the oceans was available to react chemically with oxygen, which kept oxygen from accumulating in the ocean and atmosphere. Once all of the dissolved iron was used up, the oxygen released by photosynthetic organisms could escape directly into the atmosphere. As gaseous oxygen built up, the atmosphere began to change from one that was chemically reducing to one that was oxidizing (i.e., rust-forming), like today’s.
“(This is seen today in) Banded iron formations in rock, which are silica-rich and iron-rich sedimentary layers in what was sea floor.”
Exactly. The amount of oxygen tied up in banded iron formations kept Cyanobacteria busy for “the boring billion”.
Hasn’t this been known for quite some time?