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25 October 2019
Friday fold: Identity of a BIF
The Friday fold is a slab of banded iron formation now dwelling in the University of Washington’s Department of Earth & Space Sciences. But where did it come from? India? Brazil? Perhaps you can help identify its provenance.
19 July 2019
Friday fold: Banded iron formation from the University of Wisconsin geology museum
A final Friday fold from Madison, Wisconsin: this one a slab of cut and polished banded iron formation from Australia: What exquisitely beautiful rock! Happy Friday!
2 February 2017
Banded iron formation in Barberton Mountain Land
Banded iron formation is an “extinct rock” that can be found in ancient marine strata such as those found in the Barberton Greenstone Belt. Visit an outcrop on the Barberton GeoTrail and contemplate the bizarre anoxic world that Earth used to be.
28 October 2016
Friday fold: “the eye of Sauron” at Sibubule
Have a look at this week’s Friday fold – but be aware that it will be looking back!
29 March 2016
Four new GIGAmacro images
Here are a few new images I’ve been working on with my home-based Magnify2 imaging system from GIGAmacro. Archean basement complex gneiss from the Gallatin Range of Montana: Link (If this looks familiar, that’s because one of the samples I imaged with the Photoscan 3D modeling technique and published on Sketchfab the week before last.) Banded iron formation from Minnesota with ooids and stromatolites: Link Intrusion breccia: Link Blue Ridge …
18 October 2013
Friday fold: Sliced BIF from Joburg
The Friday fold is a trio of hand samples of folded banded iron formation from South Africa. Collected in 2012 as float from the “contorted bed” outcrop in downtown Johannesburg, these samples are only now being cut and polished in the lab at NOVA.
30 August 2013
Friday fold: Archean BIF from Montana
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 …
24 May 2013
Friday folds: three lovely specimens from the Carleton College rock garden
I was up in Carleton College (Northfield, Minnesota) for most of the week, working on a new teaching module for the InTeGrate project. On the way between our work area and the cafeteria where we ate lunch, we passed the geology department’s rock garden. They have some great specimens there, some big, some small. Here are three that featured folds: Closer in, you can note an exquisite example of differential …
29 May 2012
Snowball students visit the University of Maryland
The final meeting of my spring semester Snowball Earth class was a field trip to the University of Maryland, hosted by Snowball guru Jay Kaufman, a specialist in chemostratigraphy using stable isotopes. Here, Jay welcomes the class to his wet lab: Doing chemostratigraphy takes lots of samples. Here’s a drawer full of samples from one of Jay’s many field areas: Then it was time for show and tell. Jay brought …
6 February 2012
Folded BIFs of Soudan, Minnesota
Why are these people smiling? photo by Yvette Kuiper Because they are structural geologists, and they are psyched to be at an extraordinary outcrop: This is a famous pavement outcrop of polyphase-folded banded iron formation (BIF) near Soudan, Minnesota. I went there last fall before the annual meeting of the Geological Society of America, on the Structural Geology of the Superior Craton’s sub-province boundaries field trip. “Oh YEAH!” What you’re …
Callan Bentley is Associate Professor of Geology at Piedmont Virginia Community College in Charlottesville, Virginia. He is a Fellow of the Geological Society of America. For his work on this blog, the National Association of Geoscience Teachers recognized him with the James Shea Award. He has also won the Outstanding Faculty Award from the State Council on Higher Education in Virginia, and the Biggs Award for Excellence in Geoscience Teaching from the Geoscience Education Division of the Geological Society of America. In previous years, Callan served as a contributing editor at EARTH magazine, President of the Geological Society of Washington and President the Geo2YC division of NAGT.