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7 March 2014
Happy Friday! Here’s a beautiful folded obsidian sample, replete with conchoidal fractures, on display outside the geology department at Arizona State University in Tempe, where I was last week:
28 February 2014
For the Friday fold, let’s journey back to the Silurian, as exposed in the limestones of that age that were deformed during Alleghanian mountain-building (Pennsylvanian and Permian), and exposed along Corridor H in eastern West Virginia. Some buckling (cuspate-lobate form) seen in that one… A little pop-up with hinge collapse: And, finally, as a digestif, consider this little morsel: That’s a bite-sized Friday fold. Have a good weekend!
21 February 2014
Howard Allen, a blog reader from Canada, digitized a bunch of folds for us from his old Kodachrome slides. You’ll be seeing selections from these images over the weeks to come. Get psyched! There are some great folds in this batch. Here’s the first: Howard’s description: 3D folded marble, Shuswap Metamorphic Complex, north of Sicamous, British Columbia. Specimen was bulldozed out of the way for a logging road. Photographed in …
14 February 2014
Scott Johnson contributed this special “Valentine’s Day” edition of the Friday fold: a lovely primary igneous structure that evokes a heart: That’s a close-up view (lens cap for scale) that Scott took when he GigaPanned this feature: link … the big obsidian flow at Newberry Crater in Oregon. That’s a really dry lava flow that oozed out of the Earth sometime in the past thousand years or so. It’s even …
7 February 2014
I ran out of folds last December, I asked for help on Twitter. Laura Hamilton was among the first to respond, with a link to this image: @callanbentley Hartland Quay, Devon UK. Huuuuge chevron folds! pic.twitter.com/7bhRfLib9Y — lau.rah (@hammijam) December 23, 2013 Thanks, Laura, for another great image!
31 January 2014
Todd Redding is our genorous sponsor for this week’s Friday fold. Todd reports that this boulder is derived from the Okanagan Metamorphic Complex near Penticton, British Columbia, Canada. He gives its lat/long as 49°28’14.10″N, 119°30’23.14″W. Did you spot the small fault in there, too? Thanks for sharing, Todd!
24 January 2014
Reader Eric Fulmer contributed this week’s Friday fold. It’s a beauty! Eric writes that this outcrop is from “the Belgian Ardennes near Durbuy. There’s a well-exposed anticline along the Ourthe River. The stone is late-Devonian limestone typical of the immediate area that was later deformed regionally due to the Variscan orogeny. The Ardennes are classic fold-and-thrust belt, much like our Valley-and-Ridge province.” Very cool indeed. Thanks for sharing, Eric!
17 January 2014
Another guest Friday fold – again, from the structural geologist Christie Rowe at McGill University in Montreal: Christie describes this as: growth faulting in beautiful fluvial sediments… Accordingly, I have squinted and annotated it a bit: Happy Friday!
10 January 2014
Another guest submission for the Friday fold. This one comes to us from Christie Rowe, and it shows a tiny kink fold in the Bitter Ridge formation (playa limestones):
3 January 2014
My former student Aaron Barth sent me a few photos of disharmonic folding in metamorphic rocks in Ireland for a guest Friday fold…. Awesome! Thanks Aaron!