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15 September 2017

Friday fold: Dextral asymmetry in a shear zone, Italy

The Friday fold comes from highly foliated rocks in a shear zone near Tyrol, Italy. It was contributed by reader Samuele Papeschi.

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8 September 2017

Friday fold: Ptygmatic folding in gneiss

I was transferring some samples into my structural geology cabinet last week when I found this beautiful ptygmatic (“intestine-like”) folded quartz vein. I thought it deserved some wider circulation. I can’t recall where it came from, but it’s beautiful, with a train of a dozen or so isoclinal folds. So I made the digital media you see below. Enjoy! Here’s a GIGAmacro of the sample (you need Flash enabled to …

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18 August 2017

Friday folds: the Roman Forum

When in Rome, do Friday folds as the Romans do? Here are some images from my brief, sweltering visit to the Roman Forum(s) this past summer. The whole region is a jumblepile of ancient ruins in a thousand styles. Almost nothing is labeled. It looks like this: This particular building held up a bit better, and its lovely columns sported some folded marbles: Close-up shots to show the folding internal …

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11 August 2017

Friday fold: Eagle Rock

For the Friday fold, Callan digs out images of Eagle Rock, Virginia, well aged in his digital archive for a decade!

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9 August 2017

A suite of new 3D models

A showcase of five new 3D digital models of awesome rock samples and outcrops, produced using Agisoft Photoscan.

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4 August 2017

Friday fold trio: Samples from UNM, ABQ

It’s Friday and that means “fold time” here at Mountain Beltway. Today, we feature a trio of samples on display in the halls of the Department of Earth and Planetary Sciences at the University of New Mexico.

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28 July 2017

Friday fold: Big kink fold in Grinnell Formation

It’s Friday! How about we celebrate with a beautiful kink fold from a gorgeous national park?

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21 July 2017

Friday fold: Sardinia

My friend Ander Sundell at the College of Western Idaho is the source of today’s Friday fold. It’s from somewhere in Sardinia, and I think you’ll find it visually striking: Ander says: The rocks here are Silurian phyllites generated from mudstones that were deposited on the floor of the rheic ocean basin. The color and grain size variation do an excellent job highlighting compositional layering. They were deformed during the …

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14 July 2017

Friday fold: chevrons in the Scaglia Rossa, Apennines

The Friday fold visits the Apennine Range of central Italy.

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7 July 2017

Friday fold: marble in a thermopolium at Herculaneum

It’s Friday. Let’s find a historic sort of Friday fold in the ruins of Herculaneum, Naples, Italy.

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23 June 2017

Friday fold: Canoeing the Célé River, France

I was in southern France last week, exploring an awesome suite of caves cut into the Causses limestone plateau. My family and I took an afternoon to paddle a canoe down 5 kilometers of the Célé River. While floating along, we spied a gentle, open fold in the limestone layers that crop out along the banks. This low-amplitude fold is highlighted with the “horizontal” reference line of the river’s edge. …

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16 June 2017

Friday fold: toothpasty Tomstown

I spent last weekend at the National Association of Geoscience Teachers’ Eastern Section meeting, based out of the Community College of Baltimore County in Catonsville, Maryland. One of the two field trips I took headed out to the western Piedmont, Blue Ridge and Valley & Ridge provinces of western Maryland. On that trip, we took a tour of Crystal Grottoes, a commercial cave south of Boonsboro. I was impressed at …

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9 June 2017

Friday fold – or is it a fauxld?

Check this out: is it a fold? Annotated to show the 3D expression of the ‘bed’ (left) and cross-sectional view (right): Here’s a 3D model of the outcrop to better convey its shape: [sketchfab id=”7a5a02f9521d45dab56b2464a37c8dd9″ start=”0″ spin=”” controls=”0″] This is in the same sandstone unit I blogged about on Tuesday with the apparent soft-sediment deformation. This could be another example of the same general class of pre-lithification structures, or it …

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26 May 2017

Friday fold: Macigno turbidites II

It’s Friday. We return to Italy’s Macigno Formation for a fold, courtesy of blog reader Samuele Papeschi.

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22 May 2017

Monday Geology Picture: A Vineyard & the Cape Fold Belt

For this week’s “Monday Geology Picture” here’s a view of the Cape Fold Belt with a vineyard in the foreground. I took this picture yesterday when I took a short walk with some friends through a vineyard located in the Stellenbosch winelands, just outside of my home city of Cape Town. You can see some impressive folding in those distant mountains!

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5 May 2017

Friday fold: sea monster in stone

It’s Friday, the end of the workweek, but also the beginning of the celebration of folded rocks. Examine a particularly sinuous example from the buckled Cambrian limestones of Canada’s Kootenay National Park.

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28 April 2017

Friday fold: Two more from the Lewisian gneiss of Scotland

Happy Friday! Here are two more folds in gneisses of the Lewisian, in the North West Highlands of Scotland, near Tarbet. Enjoy!

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21 April 2017

Friday (coal)d

Often I feature a fold photo here on Friday, but today I give you a folded coal, so therefore a “coald” – this is from the Pennsylvanian Conemaugh Formation on the Alleghany Plateau in West Virginia, near Bismarck. Photo by Sebastian Andres Kaempfe Droguett.

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7 April 2017

Friday fold: paper demo

The Friday fold is a sheet of paper. Yes, really!

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27 March 2017

Cleaved, boudinaged, folded Edinburg Formation southwest of Lexington

Explore a dozen photos highlighting the structural geology of an outcrop of limestone and shale near Lexington, Virginia. Cleavage refraction, overturned beds, boudinage, folds, and even a small fossil – we’ve got something for everyone. Bring the whole family!

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