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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!

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11 July 2019

A submarine slump complex at Sandy Cove, Newfoundland

Traveling in Newfoundland, Callan visits a seaside outcrop showing a Proterozoic submarine slump complex, overprinted by tectonic cleavage and weathered by the sea.

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21 June 2019

Friday fold: The University of Wisconsin rock garden

I’m at a workshop in Madison, Wisconsin, this week. I took the lunch hour today and walked over to the geology department to check out their rock garden and geology museum. I was pleased to find a Friday fold in the rock garden: a limestone with cherty nodules/layering that has been folded…. Bonus: some nice bookshelfing/boudinage of the chert: …And here’s another boulder of the same lovely stuff. And here …

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14 June 2019

Friday fold: kinked cleavage at Harpers Ferry

Last weekend was the annual meeting of the eastern section of the National Association of Geoscience Teachers. On Friday afternoon, we visited Harpers Ferry, West Virginia, and my colleague Beth Doyle led a great field trip to examine the rocks exposed there. This was my favorite outcrop we saw: Here is a close up of this outcrop, which is framed by (anthropogenic) rock wall: Dipping shallowly from upper left to …

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31 May 2019

Friday fold: Point Arena, California

It’s Friday, and I’m grateful that Bret Leslie of the NRC has stepped up with a Friday fold contribution from coastal California: Bret says this outcrop is: from my trip last month to the Sonoma and Mendocino coast. The first is the cliff below the Pt. Arena lighthouse. The marine deposits (now a marine terrace) are unconformably on top of the folded Miocene sedimentary rocks in the second photo. Here …

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24 May 2019

Friday fold: Riffelhorn (+xenolith)

Naomi Barshi shares this “deskcrop” Friday fold… Naomi says she found this fold: near the Riffelhorn, Gornergrat, above Zermatt, Switzerland. The sample has befriended my other show-off sample of a mantle xenolith from San Quintin, Baja California. Thanks for sharing, Naomi! The xenolith is a nice bonus!

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17 May 2019

Friday fold: Found folds

This week, for Friday folds, I offer up some random folds that have passed my perceptual transom this week. First up: In the new Netflix series Our Planet, in episode 7 (Fresh Water), an anticline/syncline pair makes a brief appearance as David Attenborough discusses glaciers as a reservoir for fresh water. Here is a screenshot: I’m not sure where this is in the world: Greenland? Antarctica? Let me know in …

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3 May 2019

Friday fold: Monarch Canyon

When a dike is subjected to shear, how does it deform? A guest Friday fold from Darrel Cowan of the University of Washington teaches a nice little lesson. Join the field trip in Monarch Canyon of Death Valley National Park…

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26 April 2019

Friday fold: Black Sands Beach

The Friday fold can be found in a boulder of gray chert layers on Black Sands Beach, at Marin Headlands in California.

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19 April 2019

Friday fold: Angel Island “III”

For the third Friday in a row, “Mountain Beltway” features folds from Angel Island, in northern San Francisco Bay, California, This time, it’s meta-cherts on Perles Beach, showing impressive metamorphic recrystallization reactions.

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