Well here is your chance. You have hinted around at banded iron and basement rock without ever really making a point or even being clear in where you were going. Your last statement seems to indicate that this was a deliberate debating ploy. Seems strange to me to attempt debate by purposely being vague and unclear. But when you have no facts on your side, I suppose that it is all you can do.
So let's put things into perspective. I had asserted that the early atmosphere was reducing and only later became oxidizing. You disagreed and made your cryptic reference to banded iron.
So let's review and expand my line of reasoning.
In the oldest rocks, up to about 2.5 billion years ago, we find materials that formed under anoxic conditions showing that the atmosphere contained very little to no free oxygen. What are some of these materials?
Well, let's look at one, first, because I think that I see a strawman coming from you on this one. Prior to the large banded iron formation formed 2 - 2.5 billion years ago, there are other iron formations. But these formations contain incompletely oxidized iron which again confirms my assertions. If the atmosphere were oxidizing, they would have been completely oxidized as the later large iron deposits were.
We have also discussed how uraninite is found in thick deposits in formations older than 2.5 billion years of age. Uraninite can only form such deposits in anoxic conditions.
We also discussed similar deposits of pyrite, which can only form under anoxic conditions. There is an important detail to add. Some of the deposits of pyrite show signs of weathering, meaning that they spent time exposed at the surface. If conditions had been oxic, they would have oxidized.
And let's add another. Paleosols from before 2.5 billion years old that contain cerium have it in an unoxidized form. It would be impossible to have soil in an oxidizing atmosphere in which the cerium did not also oxidize.
Finally, the great banded iron formations themselves of 2 - 2.5 billion years old. These bands of iron, in contrast to the earlier bands of iron, are completely oxidized and represent the time when life evolved that gave off oxygen. The new oxygen in the water oxidized the dissolved, reduced iron. Iron oxide is basically insoluable so it precipitated out.
So Bob, tell us what banded iron formations of which you speak.
Tell us what their oxidation state is, it is important.
Tell us what you mean by basement rock. Tell us what area this basement rock is from.
Tell us where those great beds of iron came from if the atmosphere were never reducing to allow the reduced iron to dissolve in the oceans.
Tell us how all these materials that can only form in anoxic conditions were able to be formed if the atmosphere were never anoxic, especially those that show signs of being at the surface for extended periods.
Let's hear it Bob. We have heard hints, rumors and allegations that you can build a case using banded iron that there was never a period with a reducing atmosphere. Well, do it. And deal with all the counter evidence I have already presented.
Oh, and I have one more thing for you. References. Please try to have some peer reviewed, published references.
Murakami, T., Utsinomiya, S., Imazu, Y. and Prasad, N. (2001). "Direct evidence of late Archean to early Proterozoic anoxic atmosphere from a product of 2.5 Ga old weathering." Earth Planet. Sci. Lett., 184(2): 523-528.
Rasmussen, B. and Buick, R. (1999). "Redox state of the Archean atmosphere: Evidence from detrital heavy minerals in ca. 3250-2750 Ma sandstones from the Pilbara Craton, Australia." Geology, 27(2): 115-118.
