30 August 2013

Friday fold: Archean BIF from Montana

Posted by Callan Bentley

My NOVA colleague Shelley Jaye brought this gorgeous banded iron formation fold back from the Archean of Montana:


Gorgeous to think about what this rock represents: (1) an anoxic atmosphere, a world where iron was able to dissolve in seawater; (2) some addition of oxygen, causing the iron to precipitate out as iron oxide minerals, (3) burial to some enormous depth where rocks behave gooey-like, (4) tectonic stresses that caused the ductile rock to fold, and (5) uplift and exposure on Earth’s surface, where a few billion years after it initially formed, Shelley picked it up and brought it back to amaze our students…

Happy Friday!