Siliceous Sediments, Ironstones, and Phosphates (April 9 & 11)

Chert is not a big topic on the Web. Wikipedia’s article on chert is scholarly but short. An amateur has put together a very detailed page on flint and chert (and what may or may not be the differences between the two). The most important ironstones are the banded iron formations (BIF) that form the bulk of Michigan’s iron industry. Wikipedia’s page on banded iron formations is accurate and well-sourced. Nothing very exciting, but note that BIF includes chert. Phosphorites are less common on the Web. At least we can bring in the “Phosphorite War” in Estonia! Oh, and Peak Phosphorus is another future calamity you can now worry about. Otherwise I must say this is a rather boring week for our webpages. Good time to work on your research paper.

Remember that Essay #2 is due on Thursday, April 11, at 7:30 am in your Dropbox folder.

Banded Iron Formation specimen from Upper Michigan. (Click to enlarge.)

Geology in the News –

For the extraordinary story about the end-Cretaceous extinction deposits recently described in North Dakota, first read this BBC account, which is typical of the hundreds of news stories about the finds. Next read this long but entertaining story in The New Yorker. Finally for a more mixed (and realistic) appraisal, read this news article in the journal Science. It is becoming a fascinating scientific and cultural narrative. [Update: Another  perspective on this story.]

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