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27 October 2017

Friday fold: Quantankerous veins

What does it mean for a vein to be “quantankerous?” Well, to start with, it’s quartz. Second, it has to be disagreeable or cantankerous. This vein, seen in meta-arkose of the Catoctin Formation near the summit of the Blue Ridge at Rockfish Gap (not Afton Mountain), is such a quantankerous individual: You’ll notice its “S” shape, which might imply top-to-the-left kinematics. But just down the outcrop is this set of …

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29 September 2017

Friday folds: soft sediment deformation in thin sections of MTD sandstone

The Friday folds are small soft-sediment deformational features within a dismembered, folded sandstone (a “ploudin”) from a mass transport deposit from the latest Devonian of West Virginia.

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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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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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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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17 February 2017

Friday fold: Buckled at Baltinglass

Garnetiferous beds from the aureole of the Leinster Granite east of Baltinglass, County Wicklow, Ireland (Declan De Paor’s senior thesis mapping area, 1973). Manganese-rich metasediments. The prominent ‘elasticas’ or fan folds (folds with a negative inter-limb angle) are superimposed on isoclinal folds: so the brownish layer at top and bottom are the same, though that is not obvious from the image. This is a sample from the structural geology collection …

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26 January 2017

Dore Holm

The scenic arch of Dore Holm (“Door Island”) in Shetland shows off the most efficient way of breaking a slab of rock. The island’s shape is a reflection of the parsimonious nature of natural deformation.

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16 January 2017

Shear zones in Scottish gabbros

A quest to visit the “first shear zones” described in the scientific literature leads to an alternate location, and some GIGAmacro images of samples from the real, original spot.

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30 December 2016

Friday fold: one from the archive

As noted previously, my colleague Declan De Paor recently retired from Old Dominion University, and I was lucky enough to inherit some of his rock samples. I’ve been making super-high resolution images of the samples ever since. Here’s a particularly striking fold, weathered out differentially. Enjoy exploring it – and have a happy final Friday of 2016! Link 2.04 Gpx GIGAmacro by Callan Bentley (If the embedded GigaPan doesn’t work …

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