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Archive 1

Deleted text

please give a citation for the assertion that the total oxygen worldwide in banded iron formations is about 20 times the amount in the atmosphere.

  • The following text has been perhaps hastily deleted: "Banded iron formations and calcite formations were deposited at the same time from magma that also formed the first land mass made of granite. These three rock formations were distilled out of the magma in a very different ocean than we see today. It was hot and rich in carbon dioxide and magma give up iron and calcium to the early ocean at a much greater rate than it does now. What was left was granite which is less dense than magma and so to tended to rise and form the bed rock that the iron settled upon."
Some such characterization of the iron-rich ocean waters would help make this article less impenetrable. --Wetman 07:19, 5 December 2006 (UTC)

I removed it because it was simply very confusing and rather full of errors - it made the subject even more impenetrable. Now, I agree that the article is in need of some clarification and de-impenitralation. Someday maybe... Vsmith 16:38, 5 December 2006 (UTC)

The author of the above bit has questioned my removal (on my talk page). So I will address some of the errors and confusing points.
Banded iron formations and calcite formations were deposited at the same time from magma that also formed the first land mass made of granite.
The BIFs were sedimentary deposits - not magamtic. Calcite formations? are not there as far as I know. The carbonates associated with BIFs were siderite and dolomite. The BIFs are associated with greenstone belts, areas of metamorphosed basaltic volcanism. I don't think they were directly related to granites.
...rock formations were distilled out of the magma in a very different ocean than we see today.
They were not distilled out of the magma. The ocean was different in that it was lacking in oxygen and had abundant reduced iron is solution. Perhaps the most abundant component of BIFs is the chert. It has been proposed that the alternating iron oxide layers and chert layers represent a fluctuating oxygen content as photosynthesising algae waxed and waned. The iron has been postulated to be of hydrothermal origin, whereas the silica for the chert layers may be either of hydrothermal or continental weathering origin.
What was left was granite which is less dense than magma and so to tended to rise and form the bed rock that the iron settled upon.
This sentence is essentially meaningless - the iron depleted magma rose and the BIFs derived from it was deposited on the granite?
Now maybe I'll get around to adding more detail to the article based on some of my comments above and based on some good references available - someday. Vsmith 02:11, 7 December 2006 (UTC)
Also, the added bit was not sourced and neither are my comments above (largely from memory). When I get 'round to-it, (adding to the article that is) I'll back up my memory with solid references. Cheers, Vsmith 02:20, 7 December 2006 (UTC)
"The banded iron formations are our first glimpse into an aspect of Earth's paleoecology." I'm an amateur, but wouldn't that make a useful topic sentence? --Wetman 16:47, 5 December 2006 (UTC)
Something along those lines would work - tie in to atmospheric evolution as well. Vsmith 02:11, 7 December 2006 (UTC)

I will admit the facts are confusing and will attempt to fix the problem. The first thing to consider is the current placement of the CO2. It is very clear there is a lot of CO2 in the rock formations made of calcium and magnesium. That CO2 came from somewhere as the chemical reactions occured. The reactions only happen when the right environment is in place. The ocean is where it happened and that means the ocean was very different than it now is. The magma is the source of calcium and magnesium and when CO2 is available and given the right environment calcite and dolemite form. The iron also in the magma desolves as you say into an iron rich ocean and no oxygen. Now, doing a bit of math we find the total CO2 was ~10E20 kilograms or more. All that CO2 was in the atmosphere in the beginning. That means the atmosphere was more than 20 times as dense as now so the pressure at sea level was 20 times more than now. You are not going to find a lot of detail about any of this except in the rocks and I only read what others say they find as I see nothing when I look at the rocks. If they are right then at some time about 4bya there was no land and then land started to rise from the seabed as granite because granite is less dense than magma. The BIFs were then able to settle out in shallow water. Calcite/dolemite also formed at that time as a part of the same complex process.—Preceding unsigned comment added by User:Jimhmeyer (talk • contribs) 03:06, 12 December 2006 --Jo (talk) 21:02, 8 March 2008 (UTC)

diurnal cycles for banding?

The ashtray photo caption says "The red layers were laid down during the daylight hours when Archaean photosynthesizing cyanobacteria produced oxygen that immediately reacted with dissolved iron compounds in the water, to form insoluble iron oxide (rust). The white layers are sediments that settled during the night when there was no oxygen in the water" and references #7, Margulis & Sagan pp. 81-83. The reference does talk about alternating layers, but due to "seasonal and climatic shifts", not diurnal cycles. I'd be very interested in a reference for diurnal cycles here. — Preceding unsigned comment added by 71.193.193.77 (talk) 23:36, 2 June 2015 (UTC)

Effect of asteroid impact?

I wonder if this topic is given WP:undue weight? I say this as the hypothesis seems pretty far-fetched -- but I don't know the area, and the only cite is a paper-only(?) journal.

Ah, here's an online copy: PDF. It's a respectable publication, but not much cited per Google Scholar, so apparently hasn't really caught on. Comments? At the least, this section needs a rewrite. TIA, Pete Tillman (talk) 20:23, 13 April 2016 (UTC)

I agree it has been given undue weight. Two sentences -- one describing the idea, and another (with reliable sources) explaining why it has not caught on -- is sufficient. --Kent G. Budge (talk) 17:27, 16 June 2020 (UTC)
Yes, undue weight. The authors themselves don't even mention their idea in this later paper, where the Sudbury Impact Layer plays a role only for dating. Two or zero sentences? --Rainald62 (talk) 15:31, 18 September 2022 (UTC)

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Other theories for the Banded Iron Formations

Just to say, might be a good idea to mention some of the other theories. Including:

  • UV photo-dissociation [1] and [2] (in the section UV-Photooxidation Model)
  • Formation from black smokers (hydrothermal vents) [3]

Robert Walker (talk) 16:05, 14 July 2017 (UTC)

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What's needed to make this a Good Article?

This is one of a dozen geology articles that is rates as top importance, but start quality. What are some things that are needed to bring it up to C-class quality? (Or is it there already?)

My thoughts:

  • Would like a bit more on occurrences, giving more details both on locations and geologic times.
  • Would like a bit more on chemistry, if there is more that is known than is given here. Why magnetite versus hematite, for example?
  • More on what the cyclicity is attributed to. There are only bare-bones mentions of theories.
  • More on BIFs as an economic resource. This is the major supplier of the most important metallic element for industrialized societies, after all.

Other thoughts? --Kent G. Budge (talk) 17:31, 16 June 2020 (UTC)

Started working this article over, beginning with a solid lead section that summarizes basics and stands alone but leaves details to main body. This is rated a top-importance article; I mean to make a focused effort to bring it to GA status. Will welcome all suggestions and help, of course. --Kent G. Budge (talk) 19:20, 16 June 2020 (UTC)

So I spent a week immersing myself in BIF until I had BIF-on-the-brain, and did some extensive rewriting. If I may be pardoned for saying so, I think it's a big step towards GA status. If any of y'all feel comfortable rerating it, do so. I'm hesitant to rerate my own work. @GeoWriter:, I appreciate your proofreading.

So here is my take on where the article stands and what might still be needed to bring it to GA status.

  • Lead section. I think this is very solid now. It nicely summarizes the essentials without going into details that should be left in the main body. A person reading the first paragraph will have a clear idea what the article is about. A person reading the whole lead section will have a Jeopardy-level understanding of the concept. (A student asked on a test "What is a BIF and why are they important?" would probably get full credit if he simply parroted the lead section.)
  • Description. I think this is also fairly solid. However, I have one nagging worry: A lot of the literature simply speaks of "iron-formation", particularly the literature from outside North America, and the Australians (in particular) like to split iron-formation into BIF and GIF with the iron formations of the Great Lakes listed as GIFS and not BIFs at all. On the other hand, GIFs and BIFs all get rolled into BIFs by some (mostly North American) geologists. Should the article be moved to "Iron formation" and this distinction more emphasized? I'd say no, but I think the possibility should at least be mooted.
Also, one datum this section lacks is what distinguishes Neoproterozoic BIFs from earlier types. I have the sense there are some morphological differences of significance that perhaps ought to be sourced and mentioned.
  • Occurrence. I think we're solid here as well. I do wonder if we ought to have a map of occurrences. I did a hand copy (so to speak; I used Grace) of Trendall's graph, which I think qualifies as an independent work free of copyright; I could do something similar for locations, but that makes me a touch nervous unless I make it a Wiki map. Can those include multiple locations and symbols?
  • Origin. Here I think it starts to be less solid. I think the basic facts are there; perhaps they just need some reorganizing and extension. I recall one source presenting evidence that the original precipitation reaction is directly to hematite, so perhaps that reaction should be included. This would also mean saying more about diagenesis. Perhaps a better organization to call out the differences between non-biological and biological theories, and between anoxygenic and oxygenic biological theories. Would appreciate someone else taking a stab at this; my brain is starting to hurt already.
Would be nice to have an illustration of a Neoproterozoic BIF for the Snowball Earth section. The image of the river in Spain I removed because I see no indication it actually has anything to do with BIFs -- it apparently is colored with iron from a massive sulfide deposit, not the same thing at all. The image of Neoarchean BIF is really just a placeholder.
  • Economic geology. I'm wondering if we should merge in the Taconite article, since taconite is simply unweathered GIF. This would nicely fill out the economic geology section. I think we have good stuff on North American and Australian iron production from BIF, but it looks like Brazil is the second most important iron ore exporter and I'd like a section on that -- the problem being that I've not found a source that indicates to what extend Brazilian production is from BIFs or their weathering products. (I suspect most, but haven'nt found a reliable source on that.)
  • I've toyed with a "History of investigation" section, but, really, the long mention of Cloud in the "Origin" section covers what's historically most significant.

Other thoughts? --Kent G. Budge (talk) 16:28, 21 June 2020 (UTC)

Section: Occurence; Fig 2

Looking at the figure provided I can't seem to differentiate a "light yellow" from a "dark yellow." Are both represented in the picture? I only see yellow, brown, and red. Can "dark yellow" be removed from the caption?

Side question, does Wikipedia implement accessible color options? I'm sure many would find a benefit if an effort was made for accessible graphics colors. A.silentCartographer (talk) 23:52, 7 August 2022 (UTC)

I generated the original figure. Since you point it out, I can imagine that it might be hard for persons with poor color perception to distinguish the limited set of colors. I'll try to generate a new version with more strongly contrasting colors, and perhaps patterning that is distinguishable to colorblind persons. --Kent G. Budge (talk) 02:12, 8 August 2022 (UTC)

Thanks Kent. I appreciate that (and all of your contributions to geology articles that I've read over the years). I meant to refer to the map below that graphic, though.

  1. I'll have to go through your War in the Pacific encyclopedia a bit, too. Had a grandfather in the Marines from '43–'45 roughly I'd recently been trying to find out more about. Also had a great uncle who spent 3½ years as a POW starting in Corregidor and ending with the liberation of Mukden/Hoten Camp if you've got any reading suggestions. A.silentCartographer (talk) 03:29, 11 August 2022 (UTC)
Ah, okay. Yeah, that's pretty tough to distinguish. I'll switch to the same color scheme as the graph, which should make it much easier. --Kent G. Budge (talk) 04:04, 11 August 2022 (UTC)
Well, I understand now why the yellow and dark yellow look the same: They are. I'll have to go back to the sources to figure out which is which and substitute a better color scheme. Will take a little while. --Kent G. Budge (talk) 04:11, 11 August 2022 (UTC)

Hypotheses on termination

Sect. "Absence of oxygen or hydrogen sulfide" mentiones both Holland's and Canfield's hypotheses (with a reference to Holland only), while Sect. "The Great Oxidation Event" mentiones only "oxidation" (with the same reference) not including Canfield's hypothesis, since Fe in pyrite is Fe(II). I suggest to remove the second statement, to change the title of the former section to something containing "termination" or "pause", and include the primary and secondary sources ( Planavsky et al. 2018 ?). --Rainald62 (talk) 17:14, 18 September 2022 (UTC)

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